lenticel discolouration on ‘b74’ mango fruit and374759/s4269501_phd_submission.pdfthe award of...

LENTICEL DISCOLOURATION ON ‘B74’ MANGO FRUIT AND

UNDER-SKIN BROWNING ON ‘HONEY GOLD’ MANGO FRUIT

Guoqin Li

B.Sc. (Agriculture)

M.Sc. (Agriculture)

A thesis submitted for the degree of Doctor of Philosophy at

The University of Queensland in 2015

School of Agriculture and Food Sciences

i

Abstract

Lenticel discolouration (LD) on mango fruit is evident as red, brown or black ‗halos‘ surrounding

the lenticels. It is a common skin disorder on ‗B74‘ (CalypsoTM) mangoes. LD is exacerbated by

exposure to γ-irradiation, a disinfestation treatment. Postharvest treatments of ‗B74‘ fruit with

chemicals (viz., anti-browning agents: ascorbic acid, citric acid and calcium ascorbate), wax (viz.,

carnauba coatings), and bags (viz., types and atmospheres) prior to γ-irradiation were investigated

with a view to reduce LD induced by γ-irradiation. Different fruit ripeness stages (viz., hard,

rubbery and sprung) prior to γ-irradiation were also investigated. With a view to better understand

the browning biochemistry, polyphenol oxidase (PPO) and peroxidase (POD) activities and total

phenolics concentration were quantified. Anti-browning agents did not reduce LD. Coating with

three layers of 75% carnauba wax reduced LD, but the fruit failed to ripen. Maintaining fruit inside

macro-perforated bags and paper bags did not reduce LD. Holding fruit inside closed polyethylene

bags reduced LD, but only while fruit remained in the bags. Moreover, maintaining fruit in

polyethylene bags impaired subsequent ripening. Irradiating partially ripe sprung stage fruit

increased LD less that developed at eating ripe as compared to fruit treated when they were hard

green. Thus, irradiating fruit at more advanced stage of ripeness is a promising approach to reduce

LD associated with irradiation. Total fruit skin phenolics concentration was not correlated to LD.

PPO activity after γ-irradiation in hard fruit skin increased more than that in sprung fruit. Also, LD

in irradiated hard fruit skin increased more than in sprung fruit after γ-irradiation. Therefore, LD

induced by irradiation was evidently related to PPO activity. Similarly, POD activity may also be

involved in LD as it was also higher in irradiated fruit. Polyethylene bagging was associated with

reduced PPO and POD activities when fruit were in bags and for a short time after their removal.

Therefore, the transient lessening of LD after bagging is potentially associated with limited oxygen

concentrations within the bags.

Under-skin browning (USB) is manifested as sub-epidermal discolouration. This disorder

predominantly affects ‗Honey Gold‘ mango fruit. Towards understanding the causes of USB and

reducing economic losses to industry, the influences of fruit growing region (viz., Northern

Territory, North Queensland and Southeast Queensland), physical stress (viz., abrasion and

vibration [0, 3, 9 and 18 h at 12 Hz], and reduced storage temperature (viz., 6 – 20°C) were

investigated. Also, transporting fruit in soft polystyrene liner tray inserts was compared to

commercial polyethylene liner tray inserts as a potential means to reduce USB. In addition, mango

sap influences for harvest time (viz., morning, afternoon) and type (viz., spurt and ooze) were

evaluated along with holding temperature (viz., 12 and 20°C) and mechanical damage type (viz.,

ii

abraded, cut and peeled). USB incidence and severity, PPO and POD activities and total phenolic

concentrations were measured. USB incidence was strongly influenced by the fruit growing region.

Fruit grown in the Northern Territory were more susceptible to developing USB than fruit from

North Queensland. Fruit produced in Southeast Queensland had no USB. The test measure of

abrading the fruit skin elevated the incidence of USB on fruit grown in the Northern Territory and

North Queensland. Moreover, the USB area (severity) surrounding the abrasion was generally

larger than was USB expression away from the abrasion site. Simulated road transport vibration of

12 Hz for 18 h induced USB. Compared to at 20°C, vibration at low temperature increased the

incidence of USB on fruit vibrated for 3, 9 and 18 h. Therefore, USB is not simply a chilling injury

response. Physical stress is most likely to directly induce USB, and low temperature exacerbates the

disorder. However, shipment of fruit in a polystyrene liner did not consistently lessen USB

incidence and severity as compared to the polyethylene liner. As for the vibrated fruit, a higher

incidence (%) of USB was found on the ‗shoulder‘ position than on the ‗cheek‘ position. Total

phenolics concentration, and PPO and POD activities were less possible to be closely associated

with USB incidence and severity. Anatomically, USB occurred in sub-epidermal cells surrounding

resin ducts and extending away from resin ducts. Sub-epidermal browning similar to USB could be

induced by injecting mango spurt sap underneath the skin. Exposure of fruit to a low temperature of

12°C resulted in a higher incidence of browning than at 20°C. Overall, observations suggested that

physical stress possibly results in the leakage of sap from resin ducts into surrounding cells to cause

USB, and low temperature intensifies USB.

iii

Declaration by Author

This thesis is composed of my original work, and contains no material previously published or

written by another person except where due reference has been made in the text. I have clearly

stated the contribution by others to jointly-authored works that I have included in my thesis.

I have clearly stated the contribution of others to my thesis as a whole, including statistical

assistance, survey design, data analysis, significant technical procedures, professional editorial

advice, and any other original research work used or reported in my thesis. The content of my thesis

is the result of work that I have carried out since the commencement of my research higher degree

candidature and does not include a substantial part of work that has been submitted to qualify for

the award of any other degree or diploma in any university or other tertiary institution. I have

clearly stated which parts of my thesis, if any, have been submitted to qualify for another award.

I acknowledge that an electronic copy of my thesis must be lodged with the University Library and,

subject to the policy and procedures of The University of Queensland, the thesis be made available

for research and study in accordance with the Copyright Act 1968 unless a period of embargo has

been approved by the Dean of the Graduate School.

I acknowledge that copyright of all material contained in my thesis resides with the copyright

holder(s) of that material. Where appropriate I have obtained copyright permission from the

copyright holder to reproduce material in this thesis.

iv

Publications during Candidature

Conference oral presentations

Post-harvest Treatments Effects on ‗B74‘ Mango Fruit Lenticel Discolouration after Irradiation.

2014. In ‗International Horticulture Congress‘, pp. 17 ˗ 22. Brisbane, Australia.

C. Proceeding papers

Li, G. Q., San, A., Gupta, M., Joyce, D., Hofman, P., Macnish, A., Marques, R. Post-harvest

Treatments Effects on ‗B74‘ Mango Fruit Lenticel Discolouration after Irradiation. Acta

Horticulturae. (submission)

Publications included in this Thesis

Li, G. Q., San, A., Gupta, M., Joyce, D., Hofman, P., Macnish, A., Marques, R. Post-harvest

Treatments Effects on ‗B74‘ Mango Fruit Lenticel Discolouration after Irradiation. Acta

Horticulturae. (submission) - incorporated as part of Chapter 3.

Contributor Statement of contribution

Author Li, G. Q. Designed experiments (60%)

Statistical analyses of data (100%)

Wrote the paper (70%)

Author San, A. Wrote and edited paper (2%)

Author Gupta, M. Wrote and edited paper (5%)

Author Joyce, D. Designed experiments (40%)

Wrote and edited paper (8%)

Author Hofman, P. Wrote and edited paper (3%)

Author Macnish. A. Wrote and edited paper (10%)

Author Marques, R. Wrote and edited paper (2%)

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Contributions by Others to the Thesis

1. Madan Gupta (Thesis Principal Advisor; UQ Senior Lecturer): Advising on experiments and

critically revising drafts of the work so as to contribute to interpretation.

2. Daryl C. Joyce (Thesis Advisor; UQ Professor): Conception and design of the project advising on

individual experiments and critically revising drafts of the work so as to contribute to interpretation.

3. Andrew Macnish (Thesis Advisor; Queensland Department of Agriculture, Fisheries and

Forestry): Advising on experiments and critically revising drafts of the work so as to contribute to

interpretation.

4. Peter J. Hofman (Thesis Advisor; Senior Principal Horticulturist – Postharvest; Queensland

Department of Agriculture, Fisheries and Forestry): Conception and design of the project advising

on individual experiments and critically revising the draft of the work so as to contribute to

interpretation.

5. Allan Lisle (Biometrician; UQ Academic Staff): Advising on experimental design and data

analyses.

6. Kerri Dawson (Biometrician; Queensland Department of Agriculture, Fisheries and Forestry)

Advising on experimental design and data analyses

7. David Myer (Biometrician; Queensland Department of Agriculture, Fisheries and Forestry)

Advising on experimental design and data analyses

8. Roy Short (Editor, UQ): Review of thesis chapters as paid professional English editing.

Statement of Parts of the thesis Submitted to Qualify for the Award of

another Degree

None

vi

Acknowledgements

I express my profound gratitude to my advisor Professor Daryl Joyce for his outstanding guidance,

constructive advice, strict and logical attitude and inspiration in research. I am very appreciative of

Dr Andrew Macnish for, in particular, giving detailed advice on writing thesis. I immensely thank

Dr Peter Hofman and Dr Madan Gupta for also helping during my PhD studies.

I am extremely grateful to the Chinese Scholarship Council and UQ PhD Scholarship which offered

me the opportunity to undertake doctoral study in Australia. I truly appreciated for the Chinese

Scholarship Council for supporting my living expenses and for The University of Queensland for

supporting my tuition fee. The research operating costs on lenticel discolouration of ‗B74‘ mango

fruit were covered by the project MG10008 funded by Horticulture Innovation Australia (HIA)

through voluntary contribution from Harvest Fresh Fruit Company and matched from the Australian

Government. The research operating costs for under-skin browning on ‗Honey Gold‘ mango fruit

were covered by the projects MG10009 and MG13016 funded by HIA through voluntary

contribution from Pinata Farms and matched from the Australian Government.

Technical assistance from current and former staff members of the DAFF Supply Chain Innovation

Team, including Barbara Stubbings, Jonathan Smith, Ian Wells, Christine Nolan and Dr. Roberto

Marques is great acknowledged. I sincerely thank other staff members, including Jan Dean, Dr.

Elizabeth Dann and Dr. Andrew Gerring for advice and help in laboratory use. Advice and support

on statistical analyses from biometricians David Myer, Kerri Dawson and Allan Lisle are gratefully

acknowledged. I sincerely thank fellow postgraduate students Anh Tram San, Tuan Minh Nguyen

and Muhammad Sohail Mazhar who were always friendly and supportive to me. I also express my

thanks to Ecosciences Precinct journal club members of Merran Neilson, Rebecca Roach, Kein Do,

Louisa Parkinson. I reserve very special thanks for my parents, sister and brother for their moral

support throughout the period of my PhD work.

vii

Keywords

Anatomy, lenticel discolouration, low storage temperature, mango fruit, physical stress, postharvest

treatment, quality parameter, sap, under-skin browning

Australian and New Zealand Standard Research Classifications

(ANZSRC; 2008)

070605 Post Harvest Horticultural Technologies 30%

060705 Plant Physiology 40%

060799 Plant Biology 30%

Fields of Research Classification

0706 Horticultural Production 30%

0607 Plant Biology 70%

viii

Table of Contents

ABSTRACT ................................................................................................................... I

PUBLICATIONS DURING CANDIDATURE ......................................................... IV

PUBLICATIONS INCLUDED IN THIS THESIS ..................................................... IV

CONTRIBUTIONS BY OTHERS TO THE THESIS ................................................. V

STATEMENT OF PARTS OF THE THESIS SUBMITTED TO QUALIFY FOR

THE AWARD OF ANOTHER DEGREE ................................................................... V

ACKNOWLEDGEMENTS ........................................................................................ VI

KEYWORDS ............................................................................................................. VII

AUSTRALIAN AND NEW ZEALAND STANDARD RESEARCH

CLASSIFICATIONS (ANZSRC; 2008) .................................................................... VII

FIELDS OF RESEARCH CLASSIFICATION ......................................................... VII

TABLE OF CONTENTS ......................................................................................... VIII

LIST OF FIGURES .................................................................................................... XII

LIST OF TABLES ................................................................................................ XXIV

LIST OF ABBREVIATIONS USED IN THE THESIS ....................................... XXXI

INTRODUCTION .................................................................................. 1 CHAPTER 1

1.1 Mango ................................................................................................................................... 1 1.1.1 Botany ...................................................................................................................... 1

1.1.2 Economic .................................................................................................................. 2

1.2 Background ........................................................................................................................... 3 1.3 Research Hypothesis............................................................................................................. 4

1.4 Objectives ............................................................................................................................. 6 1.5 Thesis Composition .............................................................................................................. 7 References .................................................................................................................................. 7

LITERATURE REVIEW ..................................................................... 10 CHAPTER 2

2.1 Skin Browning Disorders of Harvested Produce ................................................................ 10 2.1.1 Symptoms ............................................................................................................... 10 2.1.2 Mechanism of browning in fruit ............................................................................ 10

2.2 Mango Skin Browning Disorders ....................................................................................... 14 2.2.1 Causes .................................................................................................................... 15

2.2.2 Treatments for controlling browning ..................................................................... 24 2.3 The Mechanism of Lenticel Discolouration and Under-skin Browning ............................ 35 2.4 Perspective and Conclusions .............................................................................................. 39 References ................................................................................................................................ 39

POSTHARVEST TREATMENTS EFFECTS ON REDUCING LD CHAPTER 3

AFTER Γ-IRRADIATION ......................................................................................... 56

Abstract ..................................................................................................................................... 56

3.1 Introduction ........................................................................................................................ 57

ix

3.2 Materials and Methods ....................................................................................................... 58 3.2.1 Materials ................................................................................................................. 58

3.2.2 Experiment 1. Effects of chemicals ....................................................................... 59 3.2.3 Experiment 2. Effects of waxing ............................................................................ 60 3.2.4 Experiment 3. Effects of bagging........................................................................... 61 3.2.5 Experiment 4. Effects of fruit ripeness stage ......................................................... 63

3.2.6 γ-Irradiation ............................................................................................................ 63 3.2.7 Quality assessment ................................................................................................. 64 3.2.8 Weight loss ............................................................................................................. 66 3.2.9 Titratable acidity (TA) and soluble solids concentration (SSC) ............................ 66 3.2.10 Experiment design and statistical analyses .......................................................... 66

3.3 Results ................................................................................................................................ 68 3.3.1 Experiment 1. Effects of chemicals ....................................................................... 68 3.3.2 Experiment 2. Effects of waxing ............................................................................ 73 3.3.3 Experiment 3. Effects of bagging........................................................................... 79 3.3.4 Experiment 4. Effects of fruit ripeness stage ......................................................... 95

3.4 Discussion ......................................................................................................................... 101 3.4.1 LD ........................................................................................................................ 101 3.4.2 Skin colour ........................................................................................................... 103

3.4.3 Firmness ............................................................................................................... 104 3.4.4 Weight loss ........................................................................................................... 104 3.4.5 TA and SSC.......................................................................................................... 105

3.5 Conclusion ........................................................................................................................ 105 References .............................................................................................................................. 105

EFFECTS OF FRUIT RIPENESS STAGE AND POLYETHYLENE CHAPTER 4

BAG PACKAGING ON LENTICEL DISCOLOURATION BIOCHEMISTRY

AFTER Γ-IRRADIATION ....................................................................................... 111

Abstract ................................................................................................................................... 111

4.1 Introduction ...................................................................................................................... 111 4.2 Materials and Methods ..................................................................................................... 112

4.2.1 Fruit materials ...................................................................................................... 112

4.2.2 Experiment 1. Effects of fruit ripeness stage in the 2013 – 14 season................. 113 4.2.3 Experiment 2. Effects of bagging in the 2013 – 14 season .................................. 113

4.2.4 γ-Irradiation .......................................................................................................... 113 4.2.5 LD anatomy .......................................................................................................... 113 4.2.6 Biochemical assays .............................................................................................. 114

4.2.7 Experimental design and statistical analyses ....................................................... 115 4.3 Results .............................................................................................................................. 115

4.3.1 LD anatomy .......................................................................................................... 115 4.3.2 Experiment 1. Effects of fruit ripeness stage in the 2013 – 14 season................. 116 4.3.3 Experiment 2. Effects of bagging in the 2013 – 14 season .................................. 120

4.4 Discussion ......................................................................................................................... 124


EFFECT OF STORAGE TEMPERATURE ON UNDER-SKIN CHAPTER 5

BROWNING ON ‗HONEY GOLD‘ MANGO FRUIT ........................................... 128

Abstract ................................................................................................................................... 128 5.1 Introduction ...................................................................................................................... 129 5.2 Materials and Methods ..................................................................................................... 130

x

5.2.1 Materials ............................................................................................................... 130 5.2.2 Abrasion test......................................................................................................... 130

5.2.3 Experiment 1. Effects of storage temperature and fruit size on abraded fruit in the

2011 – 12 season ............................................................................................... 131 5.2.4 Experiment 2. Effects of storage duration and fruit size on abraded fruit in the

2011 – 12 season ............................................................................................... 131

5.2.5 Experiment 3. Effects of delayed cooling on abraded fruit in the 2011 – 12 season

........................................................................................................................... 132 5.2.6 Experiment 4. Effects of delayed abrasion test on abraded fruit in the 2011 – 12

season ................................................................................................................ 132 5.2.7 Experiment 5. Effects of storage temperature, fruit growing region and abrasion

test on fruit in the 2012 – 13 season .................................................................. 132 5.2.8 Experiment 6. Effects of temperature on discs of mango fruit skin in the 2012 – 13

season ................................................................................................................ 133 5.2.9 Measurements ...................................................................................................... 134 5.2.10 Experimental design and statistical analyses ..................................................... 135

5.3 Results .............................................................................................................................. 136 5.3.1 Experiment 1. Effects of storage temperature and fruit size on abraded fruit in the

2011 – 12 season ............................................................................................... 136

5.3.2 Experiment 2. Effects of storage duration at 13°C and fruit size on abraded fruit in

the 2011 – 12 season ......................................................................................... 140 5.3.3 Experiment 3. Effect of delayed cooling in the 2011 – 12 season ....................... 141

5.3.4 Experiment 4. Effects of delayed abrasion test in the 2011 – 12 season ............. 142 5.3.5 Experiment 5. Effects of storage temperature, fruit growing region and abrasion

test in the 2012 – 13 season ............................................................................... 143

5.3.6 Experiment 6. Effects of temperature on discs of mango fruit skin in the 2012 – 13

season ................................................................................................................ 155

5.4 Discussion ......................................................................................................................... 155 5.5 Conclusion ........................................................................................................................ 157 References .............................................................................................................................. 157

EFFECT OF SIMULATED VIBRATION ON USB OF ‗HONEY CHAPTER 6

GOLD‘ MANGO FRUIT AND THE BROWNING BIOCHEMISTRY OF THE USB

RESPONSE ............................................................................................................... 160


6.2.1 Fruit materials ...................................................................................................... 161 6.2.2 Vibration calibration ............................................................................................ 162

6.2.3 Experiment 1. Effects of fruit growing region, vibration duration, storage

temperature and tray insert in the 2012 – 13 season ......................................... 164 6.2.4 Experiment 2. Effects of vibration duration, storage temperature and tray insert

(fruit grown in North Queensland) in the 2013 – 14 season ............................. 165

6.2.5 Experiment 3. Effects of vibration duration, storage temperature and tray insert

(fruit grown in the Northern Territory) in the 2013 – 14 and 2014 – 15 seasons

........................................................................................................................... 166

6.2.6 Measurements ...................................................................................................... 169 6.2.7 Experimental design and statistical analyses ....................................................... 169

6.3 Results .............................................................................................................................. 169 6.3.1 Experiment 1. Effects of fruit growing region, vibration duration, storage

temperature and tray insert in the 2012 – 13 season ......................................... 169

xi

6.3.2 Experiment 2. Effects of vibration duration, storage temperature and tray insert

type (fruit grown in North Queensland) in the 2013 – 14 season ..................... 171

6.3.3 Experiment 3. Effects of vibration duration, storage temperature and tray inserts

(fruit grown in the Northern Territory) in the 2013 – 14 and 2014 – 15 seasons

........................................................................................................................... 172 6.4 Discussion ......................................................................................................................... 185


THE ROLE OF MANGO SAP IN UNDER-SKIN BROWNING ..... 191 CHAPTER 7


7.2.1 Materials ............................................................................................................... 193

7.2.2 Abrasion, cutting and peeling preparation treatments .......................................... 194 7.2.3 Sap centrifugation ................................................................................................ 194

7.2.4 Experiment 1. Effects of sap sample, storage temperature and damage type ...... 195

7.2.5 Experiment 2. Effects of storage temperature and terpinolene ............................ 196 7.2.6 Anatomy ............................................................................................................... 196 7.2.7 Measurements ...................................................................................................... 196 7.2.8 Experimental design and statistical analyses ....................................................... 196

7.3 Results .............................................................................................................................. 197 7.3.1 Anatomy of tissue affected with USB, severe skin browning, mild skin browning

and no browning ................................................................................................ 198 7.3.2 Experiment 1. Effects of sap sample, storage temperature and damage type ...... 201 7.3.3 Experiment 2. Effects of temperature and volumes of terpinolene ...................... 217

7.4 Discussion ......................................................................................................................... 219 7.5 Conclusion ........................................................................................................................ 221

References .............................................................................................................................. 222

GENERAL DISCUSSION AND CONCLUSION ............................. 224 CHAPTER 8

8.1 Part A. LD on ‗B74‘ Mango Fruit .................................................................................... 224 8.1.1 Postharvest treatments reduce LD ........................................................................ 224

8.1.2 Mechanism of LD on fruit after γ-irradiation ...................................................... 225 8.2 Part B. USB on ‗Honey Gold‘ Mango Fruit ..................................................................... 226

8.2.1 Postharvest treatments effects on USB ................................................................ 227 8.2.2 Mechanism of USB on fruit ................................................................................. 229

8.3 Findings and Directions for Future Research ................................................................... 232

8.3.1 Lenticel discolouration ......................................................................................... 232 8.3.2 Under-skin browning ........................................................................................... 232

References .............................................................................................................................. 233

APPENDICES 1. ....................................................................................................... 236

APPENDICES 2. ....................................................................................................... 271

APPENDICES 3. ....................................................................................................... 282

APPENDICES 4. ....................................................................................................... 301

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List of Figures

Figure 1.1 Images of A: a cultivated mango tree. B: mature mango fruit ........................................... 2

Figure 1.2 Images of A: ‗B74‘ mango fruit displaying LD; B: LD close up on ‗B74‘ mango fruit; C:

‗Honey Gold‘ mango fruit exhibiting under-skin browning; D: USB close up on ‗Honey

Gold‘ mango fruit. ............................................................................................................. 4

Figure 1.3 A diagrammatic interaction model for proposed ameliorative effects of postharvest

treatments with anti-browning chemicals, waxing, bagging and fruit ripeness stages in

reducing LD induced by γ-irradiation. .............................................................................. 5

Figure 1.4 Two potentially interacting models for USB induction whereby hypothesis 1 suggests

that USB involves a ‗typical‘ chilling injury process and hypothesis 2 suggests that

mango sap from resin / latex canals (laticifers) in the fruit is involved in USB initiated

by physical damage and exacerbated by low temperature. ............................................... 6

Figure 2.1 Proposed mechanism of phenolics‘ degradation and tissue browning in fruits (Oren-

Shamir, 2009) .................................................................................................................. 11

Figure 2.2 Metabolism associated with browning induced by wounding (Saltveit, 2000) ................ 11

Figure 2.3 Maillard reaction scheme adapted from Hodge (1953) .................................................... 14

Figure 2.4 Images showing symptoms of handling issues affecting mango fruit. A: Brushing

damage (from DPI, Queensland; http://postharvest.ucdavis.edu/PFfruits/MangoPhotos);

B: Compression damage (from DPI, Queensland;

http://postharvest.ucdavis.edu/PFfruits/MangoPhotos); C: CI (from Edwards, Don

University of California, Davis; http://postharvest.ucdavis.edu/PFfruits/MangoPhotos );

D: Sapburn (from DPI, Queensland;

http://postharvest.ucdavis.edu/PFfruits/MangoPhotos). ................................................. 15

Figure 2.5 Transverse section of lenticel of ‗Tommy Atkins‘ mango fruit (Bezuidenhout et al.,

2005) ............................................................................................................................... 38

Figure 3.1 Image of ‗B74‘ mango fruit during chemical dip treatments ........................................... 60

Figure 3.2 Image of ‗B74‘ mango fruit during air-drying following dip treatment with carnauba wax

......................................................................................................................................... 61

Figure 3.3 Image of ‗B74‘ mango fruit exposed to different bags treatments ................................... 63

Figure 3.4 Image of ‗B74‘ mango fruit inside fibreboard trays prior to γ-irradiation ....................... 64

Figure 3.5 A: A significant (P < 0.001) interaction of time and irradiation for LD (n = 25). B: A

significant (P = 0.018) interaction of chemicals and irradiation for skin browning (n =

25). 100AA = 100 mM ascorbic acid, 100CA = 100 mM citric acid, 500AA = 500 mM

ascorbic acid, 500CA = 500 mM citric acid, DW = distilled water. ‗B74‘ mango fruit

xiii

from Southeast Queensland in the 2011 – 12 season were dipped into 100 or 500 mM,

citric acid or ascorbic acid and subsequently exposed to irradiation or not. Fruit treated

with distilled water were the controls. More details are presented in Table A 1.2 and

Table A 1.3. ..................................................................................................................... 69

Figure 3.6 A: A significant (P < 0.001) interaction of γ-irradiation and time on skin colour (n = 25).

B: A significant (P = 0.003) interaction of chemicals and irradiation on skin colour (n =

40). 100AA = 100 mM ascorbic acid, 100CA = 100 mM citric acid, 500AA = 500 mM

ascorbic acid, 500CA = 500 mM citric acid, DW = distilled water. ‗B74‘ mango fruit

from Southeast Queensland in the 2011 – 12 season were dipped into 100 or 500 mM,

citric acid or ascorbic acid and subsequently exposed to irradiation or not. Fruit treated

with distilled water were the controls. More details are presented in Table A 1.2. ........ 70

Figure 3.7 A: A significant (P < 0.001) interaction of irradiation and time on firmness (n = 25). B:

A significant (P = 0.013) interaction of chemicals and time on firmness (n = 10). ‗B74‘

mango fruit from Southeast Queensland in the 2011 – 12 season were dipped into 100

or 500 mM, citric acid or ascorbic acid, and subsequently exposed to irradiation or not.

Fruit treated with distilled water were the controls. More details are presented in Table

A 1.3. ............................................................................................................................... 71

Figure 3.8 A significant interaction of chemicals, irradiation and time for LD (A) (P = 0.009) and

skin colour (B) (P < 0.001) (n = 15). ‗B74‘ mango fruit from Southeast Queensland in

the 2012 – 13 season were dipped in 100 mM calcium chloride, ascorbic acid or

calcium ascorbate, 10 or 50 mM calcium ascorbate, and subsequently exposed to either

irradiation or not. Fruit treated with DW (distilled water) were the controls. More details

are presented in Table A 1.4. .......................................................................................... 73

Figure 3.9 A and C: A significant (P = 0.024; P = 0.006) interaction of concentration of wax and

time for LD (A) and skin colour (C) (n = 20). B and D: A significant (P < 0.001; P <

0.001) interaction of irradiation and time for LD (B) and skin colour (D) (n = 50). ‗B74‘

mango fruit from Southeast Queensland in the 2011 – 12 season were dipped into 10,

20, 40 or 80% carnauba wax, and subsequently exposed to either irradiation or not. Fruit

treated with DW (distilled water) were the controls. More details are presented in Table

A 1.5 and Table A 1.6. .................................................................................................... 75

Figure 3.10 A significant (P < 0.001) interaction of concentration of wax and time for firmness (n =

20). ‗B74‘ mango fruit from Southeast Queensland in the 2011 – 12 season were dipped

into 10, 20, 40 or 80% carnauba wax, and subsequently exposed to either irradiation or

not. Fruit treated with DW (distilled water) were the controls. More details are

presented in Table A 1.7. ................................................................................................ 76

xiv

Figure 3.11 A: A significant (P < 0.001) interaction of layers of wax, irradiation and time for LD (n

= 15) (A); B: A significant (P = 0.048) interaction of layers of wax, irradiation and time

for skin colour (n = 15). C: A significant (P < 0.001) interaction of layers of wax and

time for firmness (n = 30). D: A significant (P < 0.001) interaction of time, layers of

wax and irradiation for weight loss (n = 15). ‗B74‘ mango fruit from Southeast

Queensland in the 2012 – 13 season were dipped once or three times into 75% carnauba

wax for 10 s and subsequently and then experienced with either irradiation or not. Fruit

treated with DW (distilled water) were the controls. More details are presented in Table

A 1.8 and Table A 1.9. .................................................................................................... 78

Figure 3.12 A: A significant (P < 0.001) interaction of bagging, γ-irradiation and time for LD (n =

15); B: A significant (P < 0.001) interaction of bagging, γ-irradiation and time for skin

colour (n = 15). ‗B74‘ mango fruit from Southeast Queensland in the 2011 – 12 season

were enclosed in polyethylene bags with or without nitrogen flushing, and subsequently

experienced with irradiation or not, and finally removed from the bags after 24 and 48 h

storage. Fruit with no bag were the controls. More details are presented in Table A 1.11.

......................................................................................................................................... 81

Figure 3.13 A significant (P < 0.001) interaction of bagging and time for firmness (n = 30). ‗B74‘

mango fruit from Southeast Queensland in the 2011 – 12 season were enclosed in

polyethylene bags with or without nitrogen flushing, and were subsequently exposed to

γ-irradiation or not, and finally removed from bags after 24 or 48 h storage. Fruit with

no polyethylene bags were the controls. All fruit were all kept in the ripening room at

20C and 90% RH. More details are presented in Table A 1.12. ..................................... 82

Figure 3.14 A, B and C: A significant (P < 0.001; P < 0.001; P = 0.048) interaction of bagging,

irradiation and time for LD (A), skin colour (B) and firmness (C) (n = 15). ‗B74‘ fruit

from Southeast Queensland collected in the 2012 – 13 season were treated with paper

bags, macro-perforated bags, macro-perforated bags with high RH, polyethylene bags,

or polyethylene bags with nitrogen flushing, and subsequently experienced with either

irradiation or not. Fruit not bagged were the controls. Day 0 is the day of bagging and γ-

irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the quality

parameters of fruit before they were bagged and irradiated. Data on day 8 are the quality

parameters of fruit after bags were removed from them. More details are presented in

Table A 1.13 and Table A 1.14. ...................................................................................... 85

Figure 3.15 A significant (P < 0.001; P = 0.009) interaction of bagging and γ-irradiation for weight

loss on days 8 and 10, respectively (n = 15). ‗B74‘ fruit from Southeast Queensland

collected in the 2012 – 13 season were treated with paper bags, macro-perforated bags,

xv

macro-perforated bags with high RH, polyethylene bags, or polyethylene bags with

nitrogen flushing and subsequently experienced with either irradiation or not. Fruit not

bagged were the controls. Day 0 is the day of bagging and γ-irradiation treatment. Day 8

is the day of bags removal. Data on day 0 are the quality parameters of fruit before they

were bagged and irradiated. Data on day 8 are the quality parameters of fruit after bags

were removed from them. More details are presented in Table A 1.14. LSD1 is the least

significant difference for data on day 8 and LSD2 is the least significant difference for

data on day 10. ................................................................................................................ 87

Figure 3.16 A: A significant (P = 0.024) interaction of fruit ripeness stage, γ-irradiation and time for

LD (n = 30). B: A significant (P = 0.001) interaction of fruit ripeness stage, bagging and

time for LD (n = 20). C: A significant (P < 0.001) interaction of bagging, γ-irradiation

and time for LD (n = 30). ‗B74‘ mango fruit from Southeast Queensland collected in the

2013 – 14 season reached to hard, rubbery and sprung after 0, 3 and 8 days. The fruit

were then treated with polyethylene bags with or without nitrogen flushing. Fruit that

were not bagged were the controls. All fruit were subsequently exposed to either γ-

irradiation or not. Day 0 is the day of bagging and γ-irradiation treatment. Day 8 is the

day of bags removal. Data on day 0 are the quality parameters of fruit before they were

bagged and irradiated. Data on day 8 are the quality parameters of fruit after bags were

removed from them. More details are presented in Table A 1.15. .................................. 89

Figure 3.17 A: A significant (P < 0.001) interaction of fruit ripeness stage, γ-irradiation and time for

skin colour (n = 30). B: A significant (P = 0.007) interaction of fruit ripeness stage,

bagging and time for skin colour (n = 20). C: A significant (P < 0.001) interaction of

bagging, γ-irradiation and time for skin colour (n = 30). ‗B74‘ mango fruit from

Southeast Queensland collected in the 2013 – 14 season reached hard, rubbery and

sprung after 0, 3 and 8 days. The fruit were then treated with polyethylene bags with or

without nitrogen flushing. Fruit that were not bagged were the controls. All the fruit

were subsequently exposed to either γ-irradiation or not. Day 0 is the day of bagging

and γ-irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the

quality parameters of fruit before they were bagged and irradiated. Data on day 8 are the

quality parameters of fruit after bags were removed. More details are presented in Table

A 1.15. ............................................................................................................................. 91

Figure 3.18 A: A nearly significant (P = 0.05) interaction of fruit ripeness stage, γ-irradiation and

time for firmness (n = 30). B: A significant (P = 0.001) interaction of fruit ripeness

stage, bagging and time for firmness (n = 20). ‗B74‘ mango fruit from Southeast

Queensland collected in the 2013 – 14 season reached hard, rubbery and sprung after 0,

xvi

3 and 8 days and then treated with polyethylene bags with or without nitrogen flushing.

Fruit that were not bagged were the controls. All the fruit were subsequently exposed to

either γ-irradiation or not. Day 0 is the day of bagging and γ-irradiation treatment. Day

8 is the day of bags removal. Data on day 0 are the quality parameters of fruit before

they were bagged and irradiated. Data on day 8 are the quality parameters of fruit after

bags were removed. More details are presented in Table A 1.16. .................................. 93

Figure 3.19 Significant (P = 0.011; P = 0.002) interactions of fruit ripeness stage and bagging for

weight loss on day 8 and 10 (n = 10). B: Significant (P < 0.001; P < 0.001) effects of γ-

irradiation for weight loss on day 8 and 10 (n = 90). ‗B74‘ mango fruit from Southeast

Queensland collected in the 2013 – 14 season reached to hard, rubbery and sprung after

0, 3 and 8 days. They were then treated with polyethylene bags with or without nitrogen

flushing. The fruit that were not bagged were the controls. All the fruit were

subsequently exposed to either γ-irradiation or not. Day 0 is the day of bagging and γ-

irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the quality


parameters of fruit after bags were removed. More details are presented in Table A 1.16.

......................................................................................................................................... 94

Figure 3.20 A and B: A significant (P = 0.001; P < 0.001) interaction of fruit ripeness stage, γ-

irradiation and time for LD (A) and skin colour (B) (n = 10). C: A significant (P <

0.001) interaction of fruit ripeness stage and time for firmness (n = 20). D: A significant

(P = 0.011) interaction of fruit ripeness stage and time for weight loss (n = 20). ‗B74‘

mango fruit from Southeast Queensland collected in the 2013 – 14 season reached hard,

rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH,

and were subsequently exposed to either γ-irradiation or not. More details are presented

in Table A 1.16 and Table A 1.17. .................................................................................. 96

Figure 3.21 A: A significant (P = 0.012) interaction of time, fruit ripeness stage and γ-irradiation on

LD (n = 10). B. A significant (P < 0.001) interaction of time and fruit ripeness stage on

firmness (n = 20). C. Significant interactions of fruit ripeness stage and irradiation on

weight loss (%) on day 1 (P = 0.034) and 4 (P = 0.002) (n = 10). ‗B74‘ fruit in the 2013

– 14 season reached hard, rubbery and sprung fruit in a ripening room at 20°C and 90 –

100% RH after 0, 5 and 8 days, and subsequently exposed to either γ-irradiation or not.

More details are presented in Table A 1.19. ................................................................... 99

Figure 3.22 A: A significant (P < 0.001) interaction of fruit ripenessand time on skin colour (n =

20). B: A significant (P = 0.05) interaction of γ-irradiation and time on skin colour in

fruit ripeness treatments (n = 30). ‗B74‘ mango fruit in the 2013 – 14 season reached

xvii

hard, rubbery and sprung fruit after 0, 5 and 8 days in a ripening room at 20°C and 90 –

100% RH, and subsequently exposed to γ-irradiation or not. More details are presented

in Table A 1.19. ............................................................................................................. 100

Figure 4.1 Transverse unstained hand sections of LD through irradiated and ripened ‗B74‘ mango

fruit skin samples (A): [× 4], (B): [× 10], (C) [× 20] and D [× 20]. Scale bars in A, B, C

and D represent 100 µm, 50 µm, 20 µm and 20 µm respectively. RD: resin duct. L:

lenticel cavity. ............................................................................................................... 116

Figure 4.2 A: A significant (P < 0.001) interaction of fruit ripeness stage and time for total

phenolics concentration (mg GA / g FW) in skin tissue (n = 6). B: A significant (P <

0.001) interaction of irradiation and time for POD activity (units / mg Protein) in skin

tissue (n = 9); C: A significant (P < 0.001) interaction of fruit ripeness stage, irradiation

and time for PPO activity (units / mg Protein) in skin tissue (n = 3). ‗B74‘ fruit from

Southeast Queensland in the 2013 – 14 season reached hard, rubbery and sprung after 0,

3 and 8 days in a ripening room at 20°C and 90 – 100% RH. The fruit were exposed to

either 0 or 576 Gy (min – max: 493 – 716 Gy) γ-irradiation and finally kept in the

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. More details

seen in Table A 2.2, Table A 2.3 and Table A 2.3. ....................................................... 119

Figure 4.3 A significant (P = 0.024) interaction of time, fruit ripeness stage, bagging and irradiation

for total phenolics concentration (mg GA equivalents / g FW) in skin tissue (n = 3).

‗B74‘ fruit from Southeast Queensland in the 2013 – 14 season reached hard, rubbery

and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH. The

fruit were treated with polyethylene bags with or without nitrogen. The fruit not held in

bags were the controls. They were subsequently exposed to either -irradiation or not

and finally kept in the ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe. More details seen in Table A 2.5. .............................................................. 120

Figure 4.4 A: A significant (P = 0.043) interaction of time and irradiation for POD activity (units /

mg protein) (n = 18). B: A significant (P = 0.016) interaction of irradiation, fruit

ripeness stage and bagging for POD activity (units / mg protein) in skin tissue (n = 6).



fruit were treated with polyethylene bags with or without nitrogen. The fruit not held in

bags were the controls. They were subsequently exposed to either -irradiation or not

and finally kept in the ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe. More details seen in Table A 2.7. .............................................................. 121

xviii

Figure 4.5 A: A significant (P < 0.001) interaction of time, fruit ripeness stage and bagging for PPO

activity (n = 6); B: A significant (P = 0.007) interaction of irradiation and fruit ripeness

stage for PPO activity (n = 12); C: A significant (P < 0.001) interaction of irradiation

and time for PPO activity (n = 18); D: A significant (P < 0.001) interaction of

irradiation and bagging for PPO activity (n = 12). ‗B74‘ fruit from Southeast

Queensland in the 2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8

days in a ripening room at 20°C and 90 – 100% RH. The fruit were treated with

polyethylene bags with or without nitrogen. The fruit not held in bags were the controls.

They were subsequently exposed to -irradiation or not, and finally kept in the ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. More details seen in

Table A 2.6. ................................................................................................................... 123

Figure 5.1 Image of the assembly for mango fruit abrasion test application ................................... 131

Figure 5.2 Image of thermal gradient block set up with associated apparatus including water bath

unit (A), cooling unit (B), and the temperature gradient block with holes (C). ............ 133

Figure 5.3 Images of USB expression on abraded ‗Honey Gold‘ mango fruit at eating ripe. Green-

mature fruit were harvested from the Northern Territory, abraded with sandpaper,

maintained at 7C (A), 10C (B), 13C (C), 16C (D) or 20C (E) for 6 days, and then

transferred to 20C and 90 – 100% RH until they reached eating ripe. ........................ 138

Figure 5.4 Images of abraded ‗Honey Gold‘ mango fruit at eating ripe. A. Green-mature fruit were

harvested from the Northern Territory (A), North Queensland (B) and Southeast

Queensland (C), abraded with sandpaper and maintained at 10ºC and 90 – 100% RH for

8 days and then transferred to 20ºC and 90 – 100% RH until they were eating ripe. ... 143

Figure 5.5 A: A significant (P < 0.001) interaction of time, abrasion and temperature for skin colour

of fruit grown in the Northern Territory (n = 15); B: A significant (P < 0.001)

interaction of time and temperature for skin colour of fruit grown in North Queensland

(n = 30); C and D: Significant (P < 0.001; P = 0.005) interactions of time and

temperature (C) (n = 30) and of time and abrasion (D) (n = 75) for skin colour of fruit

grown in Southeast Queensland. ‗Honey Gold‘ mango fruit harvested from the Northern

Territory, North Queensland or Southeast Queensland collected in the 2012 – 13 season.

The fruit were either abraded with sandpaper or not abraded, and subsequently kept in

different rooms operating at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH for eight

days. All fruit were kept in a ripening room at 20°C and 90 – 100% RH until they

reached eating ripe. More details are presented in Table A 3.5, Table A 3.6 and Table A

3.7. ................................................................................................................................. 150

xix

Figure 5.6 A: A significant (P = 0.036) interaction of time, abrasion and temperature was

determined for firmness of fruit grown in The Northern Territory (n = 15); B: A

significant (P < 0.001) interaction of time and temperature for firmness of fruit grown in

North Queensland (n = 30); C and D: Significant (P < 0.001, P = 0.024) interactions of

time and temperature (C) (n = 30) and of time and abrasion (D) (n = 75) for firmness of

fruit grown in Southeast Queensland. After ‗Honey Gold‘ mango fruit being harvested

from the Northern Territory and North Queensland, fruit were either abraded with

sandpaper or not abraded. They were then kept at different rooms operating at 6 or 8 or

10 or 12 or 20°C, and 90 – 100% RH for eight days. Fruit were finally kept in the

ripening room at 20°C and 90 – 100% RH until they reached eating ripe. More details

are presented in Table A 3.8, Table A 3.9 and Table A 3.10. ....................................... 152

Figure 5.7 A, B and C: Significant (P < 0.001; P = 0.002, P < 0.001) effects of time (A) (n = 150),

temperature (B) (n = 120) and abrasion (C) (n = 300) on weight loss (%) of fruit grown

in the Northern Territory; D and E: Significant (P < 0.001, P < 0.001) interactions of

time and abrasion (n = 30) and of time and abrasion (n = 30) for weight loss of fruit

grown in North Queensland; F: A significant (P < 0.001) interactions of time, abrasion

and temperature for weight loss (%) of fruit grown in Southeast Queensland (n = 15).

After ‗Honey Gold‘ mango fruit being harvested from The Northern Territory and North

Queensland, fruit were either abraded with sandpaper or not abraded. They were then

kept in different rooms operating at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH for

eight days. Fruit were finally kept in ripening room at 20°C and 90 – 100% RH until

they reached eating ripe. More details are presented in Table A 3.11, Table A 3.12 and

Table A 3.13. ................................................................................................................. 154

Figure 6.1 Image of vibration table for fruit treatments .................................................................. 163

Figure 6.2 Recorded calibration frequencies (Hz) and amplitudes (cm) for the vibration table

carrying 0, 25 and 50 kg loads. ..................................................................................... 163

Figure 6.3 Images of tray inserts used in the vibration table experiments; black: polyethylene liner;

pink: polystyrene liner. .................................................................................................. 164

Figure 6.4 A: Fruit subjected to 3 h of vibration at 12 Hz in polyethylene liners (n = 16); B: Fruit

subjected to 3 h of vibration at 12 Hz in polystyrene liners (n = 16); C: Fruit subjected

to 9 h of vibration at 12 Hz in polyethylene liners (n = 16); D: Fruit subjected to 9 h of

vibration at 12 Hz in polystyrene liners (n = 16); A hard paper board was used to cover

each fibreboard tray. ...................................................................................................... 165

Figure 6.5 A, C and F: Fruit treated with 3 h of vibration in polystyrene (left half) and polyethylene

liners (right half) prior to post-treatment quality assessment (n = 8 / block and 3 blocks);

xx

B, G and H: fruit treated with 9 h of vibration in polystyrene (left half) and polyethylene

liners (right half) prior to post-treatment quality assessment (n = 8 / block and 3 blocks);

D and E: spare fruit used to maintain weight balance. An empty fibreboard tray was

placed on top of each second layer tray. ....................................................................... 166

Figure 6.6 A and D: Fruit subjected to 18 h of vibration at 12 Hz in polyethylene and polystyrene

liners, respectively (n = 15); E and H: Fruit subjected to 3 h of vibration at 12 Hz in

polyethylene and polystyrene liners, respectively (n = 15); F and G: Fruit subjected to 9

h of vibration at 12 Hz in polyethylene and polystyrene liners, respectively (n = 15); B

and C: Fruit subjected to 18 h of vibration at 12 Hz in polyethylene liners, respectively,

prior to later biochemical analysis (n = 15). An empty fibreboard tray was placed on top

of each second layer tray. .............................................................................................. 167

Figure 6.7 A and D: Each polyethylene-lined tray contained half 3 h treatment group, half 18 h

treatment group (n = 14). After 3 h of vibration at 12 Hz, half of these fruit were then

replaced by the fruit for 9 h of vibration (n = 14). These treatments were all for later

quality assessment. After 9 h of vibration, the removed fruit were replaced with spare

non-experimental fruit to maintain tight fruit contact for finishing the 18 h vibration

treatments; B and C: Each polystyrene-lined tray contained half 3 h treatment group,

and half 18 h treatment group (n = 14). After 3 h of vibration at 12 Hz, half of these

fruit were then replaced by the fruit for 9 h of vibration (n = 14). These treatments were

all for later quality assessment. After 9 h of vibration treatment, the removed fruit were

replaced with spare non-experimental fruit to maintain tight fruit contact for finishing

the 18 h vibration treatments. An empty fibreboard tray was placed on top of each

bottom layer tray. .......................................................................................................... 168

Figure 6.8 A and B: Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3 and 9 h) ,

tray insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C

[B]) (n = 8 / block and 3 blocks). ‗Honey Gold‘ mango fruit grown in North Queensland

collected in the 2013 – 14 season were vibrated for 0 (control), 3 and 9 h at either 12 or

20°C and 90 – 100% RH, and subsequently kept at 20 or 12°C, respectively, for eight

days in total. All the fruit were moved to the ripening room at 20°C and 90 – 100% RH

until fruit reached eating ripe. Data are expressed as the mean and standard error of the

mean. ............................................................................................................................. 172

Figure 6.9 A and B: Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3 and 9 h), tray

insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n

= 15). C and D: Effects on USB incidence (%) of vibration duration (0 and 18 h) and

tray insert (polyethylene and polystyrene) at different storage temperature (20 [C] and

xxi

12°C [D]) (n = 15). ‗Honey Gold‘ fruit grown in the Northern Territory collected in the

2013 – 14 season were vibrated for 3 and 9 h in the second layer and for 18 h in the first

layer at either 20 (A) or 12°C (B) and 90 – 100% RH, and subsequently kept at either 20

(A) or 12°C (B), respectively, for eight days in total. As for the four controls treatments,

fruit exposed to no vibration in different liners (polyethylene and polystyrene) were

kept at different temperatures (20 and 12°C) for eight days in total. After eight days

storage, all the fruit were moved to a ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe. ............................................................................................... 174

Figure 6.10 A and B: Effects on USB severity (rating scale) of vibration duration at 12 Hz (0, 3 and

9 h), tray insert (polyethylene and polystyrene) and storage temperature (20 [A] and

12°C [B]) (n = 15). C and D: Effects on USB severity (rating scale) of vibration

duration (0 and 18 h), and tray insert (polyethylene and polystyrene) at different storage

temperature (20 [C] and 12°C [D]). ‗Honey Gold‘ fruit grown in the Northern Territory

collected in the 2013 – 14 season were vibrated for 3 and 9 h in the second layer and for

18 h in the first layer at either 20 (A) or 12°C (B) and 90 – 100% RH, and subsequently

kept at either 20 (A) or 12°C (B), respectively, for eight days in total. As for the four

controls treatments, fruit exposed to no vibration in different liners (polyethylene and

polystyrene) were kept at different temperatures (20 and 12°C) for eight days in total.

After eight days storage, all the fruit were moved to a ripening room at 20°C and 90 –

100% RH until fruit reached eating ripe. ...................................................................... 175

Figure 6.11 Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray

insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n

=14). ‗Honey Gold‘ mango fruit grown in the Northern Territory collected in 2014 – 15

season were vibrated for 0 (control), 3, 9 and 18 h in polyethylene and polystyrene

liners at 12 and 20°C, and subsequently kept at 12 and 20°C, respectively, for eight days

in total. All the fruit were moved to a ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe. ............................................................................................... 179

Figure 6.12 Effects on USB rating scale of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =14).

‗Honey Gold‘ mango fruit grown in the Northern Territory collected in the 2014 – 15

season were vibrated for 0 (control) or 3 or 9 or 18 h in polyethylene and polystyrene

liners at 12 and 20°C, and then kept at 12 and 20°C, respectively, for eight days in total.

All the fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit

reached eating ripe. ....................................................................................................... 180

xxii

Figure 6.13 Effects on skin colour of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =14).

‗Honey Gold‘ mango fruit grown in the Northern Territory collected in the 2014 – 15

season were vibrated for 0 (control) or 3 or 9 or 18 h in polyethylene or polystyrene

liners at either 12 or 20°C, and subsequently kept at either 12 or 20°C, respectively, for

eight days in total. All the fruit were moved to a ripening room at 20°C and 90 – 100%

RH until they reached eating ripe. ................................................................................. 181

Figure 6.14 Effects on firmness of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 14).

‗Honey Gold‘ mango fruit grown in the Northern Territory were vibrated for 0 (control)

or 3 or 9 or 18 h in polyethylene or polystyrene liners at 12 or 20°C, and subsequently

kept at 12 or 20°C for eight days in total. All the fruit were moved to a ripening room at

20°C and 90 – 100% RH until fruit reached eating ripe. .............................................. 182

Figure 6.15 Effects on weight loss of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 14).

‗Honey Gold‘ mango fruit grown in the Northern Territory were vibrated for 0 (control)

or 3 or 9 or 18 h in polyethylene or polystyrene liners at 12 or 20°C, and subsequently

kept at 12 or 20°C for eight days in total. All the fruit were moved to a ripening room at

20°C and 90 – 100% RH until fruit reached eating ripe. .............................................. 183

Figure 6.16 Images of ‗light‘ USB in ‗Honey Gold‘ fruit treated with 18 h vibration in a polystyrene

liner at 20°C (A), and of ‗dark‘ USB in fruit treated with 9 h vibration in a polyethylene

liner at 12°C (B). ........................................................................................................... 185

Figure 7.1 Image of the device used to collect spurt and ooze sap from ‗Honey Gold‘ mango fruit.

....................................................................................................................................... 194

Figure 7.2 Images of symptoms caused by afternoon spurt sap topically applied at a mechanically

damaged site to a ‗Honey Gold‘ mango fruit (A), typical USB symptoms on a ‗Honey

Gold‘ mango fruit treated with 12 Hz of vibration for 9 h in soft polystyrene liner

(Chapter 6) (B) and symptoms of terpinolene damage on a ‗Honey Gold‘ mango fruit

(C). SB: Severe skin browning; MB: mild skin browning; USB: under-skin browning.

....................................................................................................................................... 198

Figure 7.3 Transverse unstained hand sections through ‗Honey Gold‘ mango fruit skin samples

treated with 12°C as affected with no USB (control; A [× 4], B [× 10]), with USB (C [×

4], D [× 10]), with severe skin browning due to terpinolene application (E [× 4], F [×

10]), with severe skin browning due to spurt sap application (G [× 4], H [× 10]) and

with mild skin browning spurt sap application (I [× 4], J [× 10]). Bars 100 μm (A, C, E,

xxiii

G and I) and 50 μm (B, D, F, H and J). Ep: epidermal cells; Sp: sub-epidermal cells;

RD: resin duct;GB: greenish browning; DBL dark browning; MB: mild skin browning.

....................................................................................................................................... 200

Figure 8.1 A schematic model on the effects on lenticel discolouration of postharvest treatments

(chemicals [anti-browning agents], bagging, waxing and fruit ripeness) prior to γ-

irradiation and the mechanism of lenticel discolouration induced by γ-irradiation. The

red arrow means ‗did not influence‘. The black arrow means ‗is related with‘. ........... 226

Figure 8.2 A schematic model on the effects on under-skin browning of postharvest treatments

(physical stress: abrasion and vibration, low storage temperature and sap) and the

mechanism of under-skin browning. The red arrow means ‗not influence‘. The black

arrow means ‗is related with‘ ........................................................................................ 231

xxiv

List of Tables

Table 2.1 Problem, causes and class of mango fruit disorders associated with skin browning ......... 17

Table 2.2 Physical factors that may reduce browning disorders (mechanical damage and CI) of

mango fruit (M. indica L.) ............................................................................................... 30

Table 2.3 Physical factors that may reduce browning disorders (heat damage and disease) of mango

fruit (M. indica L.) .......................................................................................................... 31

Table 2.4 Physical factors that may reduce browning disorder (sapburn) of mango fruit (M. indica

L.) .................................................................................................................................... 32

Table 2.5 Chemicals that may reduce browning disorder of mango fruit (M. indica L.) .................. 33

Table 2.6 Preharvest, postharvest and other factors increasing LD of fruit....................................... 36

Table 2.7 Preharvest, postharvest and other factors decreasing LD of fruit ...................................... 37

Table 3.1 Rating scales for LD severity, skin colour (based on the proportion of the non-blushed

area with yellow skin colour), firmness and skin browning of ‗B74‘ mango fruit

(Hofman et al., 2010) ...................................................................................................... 65

Table 3.2 A significant (P = 0.01) interaction of layers of 75% carnauba wax and γ-irradiation on

titratable acidity (%) at eating ripe (n = 10). ‗B74‘ mango fruit from Southeast

Queensland in the 2012 – 13 season were dipped once into 75% carnauba wax for 10 s

and then experienced with either irradiation or not. Fruit treated with DW (distilled

water) were the controls. Data are expressed as means and those followed by the same

letters are not significant at P = 0.05 according to the Fisher Protected test. More details

are presented in Table A 1.10. ........................................................................................ 79

Table 3.3 A significant (P < 0.001; P = 0.001; P = 0.027) interaction of fruit ripeness stage and γ-

irradiation on LD and skin colour at eating ripe (n = 10). ‗B74‘ mango fruit from

Southeast Queensland in the 2013 – 14 season reached hard, rubbery and sprung fruit

after 0, 3 and 8 days at ripening room at 20°C and 90 – 100% RH, respectively, and

subsequently exposed to either γ-irradiation or not. Data are expressed as mean and

those followed by the same letters are not significant different at P = 0.05 according to

the Protected Fisher test. More details are presented in Table A 1.18. ........................... 97

Table 3.4 A significant interaction of irradiation and fruit ripeness stage on LD at eating ripe based

on firmness = 3 (n = 10). ‗B74‘ mango fruit from the Northern Territory in the 2013 –

14 season reached to hard, rubbery and sprung fruit after 0, 5 and 8 days in a ripening

room at 20°C and 90 – 100% RH, and subsequently exposed to either γ-irradiation or

not. Data are expressed as mean and those followed by the same letters are not

significant different at P = 0.05 according to the Fisher Protected test. ....................... 101

xxv

Table 4.1 A significant (P = 0.034) interaction of fruit ripeness stage and irradiation for total

phenolics concentration (mg GA equivalents / g FW) in skin tissue at eating ripe (n = 3).



fruit were exposed to either 0 or 576 Gy (min – max: 493 – 716 Gy) γ-irradiation and

finally kept in the ripening room at 20°C and 90 – 100% RH until fruit reached eating

ripe. Data are expressed as mean and those followed by the same letters are not

significant. ..................................................................................................................... 117

Table 4.2 Significant effects of irradiation (n = 9) and fruit ripeness stage (n = 6) on PPO and POD

activities (units / mg Protein) in skin tissue at eating ripe. ‗B74‘ fruit from Southeast

Queensland in the 2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8

days in a ripening room at 20°C and 90 – 100% RH. The fruit at different ripeness

stages exposed to either 0 or 576 Gy (min – max: 493 – 716 Gy) and kept in the

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. More details

seen in Table A 2.1. ....................................................................................................... 118

Table 5.1 Effects of fruit size (large [12 / tray], medium [14 / tray] and small [16 / tray]) and storage

temperature (7, 10, 13, 16 and 20ºC) on AUSB, EUSB and TUSB incidence and

severity on abraded ‗Honey Gold‘ fruit at eating ripe. ‗Honey Gold‘ mango fruit of

different sizes were harvested from the Northern Territory in the 2011 – 12 season.

They were abraded with sandpaper and stored at different temperatures and 90 – 100%

RH for 6 days prior to transfer to 20ºC and 90 – 100% RH until fruit reached eating

ripe. Data are expressed as treatment means. Data followed by the same letters are not

significantly different at P = 0.05. More details are presented in Table A 3.1. ............ 139


duration (1, 3, 6 and 9 days) at 13°C on abraded fruit AUSB, EUSB and TUSB

incidence and severity (area) on ‗Honey Gold‘ mango fruit at eating ripe (n = 12, 14 and

16). Fruit of different sizes were harvested from the Northern Territory in the 2011 – 12

season. They were abraded with sandpaper and stored at different temperatures and 90 –

100% RH for 6 days prior to transfer to 20ºC and 90 – 100% RH until fruit reached

eating ripe. Data are expressed as treatment means. Data followed by the same letters

are not significantly different at P = 0.05. More details are presented in Table A 3.15.

....................................................................................................................................... 141

Table 5.3 Effects of delayed cooling of fruit on days 0, 1, 2 and 4 on the severity of EUSB and

TUSB (n = 5) on ‗Honey Gold‘ fruit at eating ripe. Fruit were harvested from the North

Queensland collected in the 2011 – 12 season. The fruit were abraded with sandpaper

xxvi

and then kept in a ripening room at 20°C and 90 – 100% RH for zero or one or two or

four days. They were then kept in a cold room at 13°C and 90 – 100% RH for six days.

Fruit with no abrasion kept at 13°C for six days were the controls. All fruit were finally

moved to the ripening room until fruit reached eating ripe. Data are expressed as

treatment means. Data followed by the same letters are not significantly different at P =

0.05. More details are presented in Table A 3.16. ........................................................ 142

Table 5.4 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on AUSB, EUSB

and TUSB incidence and severity (cm2 affected) on ‗Honey Gold‘ fruit at eating ripe.

Fruit were harvested from the Northern Territory during the 2012 – 13 season. The fruit

were abraded or not abraded with sandpaper, and then kept at different temperatures for

eight days. All fruit were finally kept in the ripening room at 20°C and 90 – 100% RH

until they reached eating ripe. Data are expressed as treatment means. Data followed by

the same letters are not significantly different at P = 0.05. NS: non-significant. More

details are presented in Table A 3.2. ............................................................................. 145

Table 5.5 Effect of abrasion test on TUSB incidence on ‗Honey Gold‘ fruit at eating ripe (n = 15).

Fruit grown in North Queensland were either abraded with sandpaper or not abraded,

and then kept at different storage temperatures for eight days. Fruit were finally kept in

a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are

expressed as treatment means. Data followed by the same letters are not significantly

different at P = 0.05. More details are presented in Table A 3.3. ................................. 147

Table 5.6 Summary of abrasion and storage temperature (6, 8, 10, 12 and 20°C) on the incidence

and severity of AUSB, EUSB and TUSB at eating ripe (n = 15). ‗Honey Gold‘ mango

fruit grown in Southeast Queensland were either abraded with sandpaper or not abraded,

and then kept in rooms at 6, 8, 10, 12 and 20°C, and 90 – 100% RH for eight days. Fruit

were then kept in a ripening room at 20°C and 90 – 100% RH until fruit reached eating

ripe. All treatments were not involved in analysis because few fruit were affected with

USB. Data are expressed as treatment means. .............................................................. 148

Table 6.1 Effects on USB incidence (%) and severity (rating scale and area [cm2 affected]) of

growing region (Northern Territory and North Queensland), vibration duration at 12 Hz

(0, 3 and 9 h) and tray insert (polyethylene and polystyrene) at eating ripe (n = 15).

‗Honey Gold‘ fruit grown in the Northern Territory and North Queensland collected in

the 2012 – 13 season were vibrated for 3 and 9 h in polyethylene and polystyrene liners

in a cold room at 12°C and 90 – 100% RH, and then kept in the same room for eight

days in total. Fruit not treated with vibration at 20°C and others at 12°C for eight days

were the two controls. All of them were then moved to the ripening room at 20°C and

xxvii

90 – 100% RH until fruit reached eating ripe. Data of incidence are expressed as mean

and data of severity are expressed as mean and standard error of the mean. ................ 171

Table 6.2 Effects of vibration duration at 12 Hz (0, 3 and 9 h), storage temperature (20 and 12°C)

and tray insert (polyethylene and polystyrene) on the incidence (%) and severity (rating

scale and area [cm2 affected]) of USB and on the incidence of USB on either ‗cheeks‘ or

‗shoulders‘ positions close to the stem (n =14) at eating ripe. ‗Honey Gold‘ mango fruit

grown in the Northern Territory in the 2014 – 15 season were vibrated for 0 (control), 3,

9 or 18 h in polyethylene or polystyrene liners at 12 or 20°C, and then kept at 12 or

20°C, respectively, for eight days in total. All the fruit were then moved to a ripening

room at 20°C and 90 – 100% RH until they reached eating ripe. Data are expressed as

mean and standard error of the mean. ........................................................................... 177

Table 6.3 Effects on PPO and POD activities (units / mg protein) and total phenolics concentration

(mg GA equivalents / g FW) of vibration for 0 and 18 h at 20 and 12°C in polyethylene

and polystyrene liners in the first layer on a vibration table and then kept at 20 and

12°C, respectively, for eight days in total (n = 3). ‗Honey Gold‘ fruit grown in the

Northern Territory collected in the 2013 – 14 season were vibrated for 18 h at 12 or

20°C and at 90 – 100% RH, and subsequently kept at 12 or 20°C, respectively, for eight

days in total. Fruit exposed to no vibration holding at 20 and 12°C for eight days were

the controls. After eight days storage, all fruit were moved to a ripening room at 20°C

and 90 – 100% RH until ripe. Data are expressed as the mean and standard error of the

mean. ............................................................................................................................. 184

Table 7.1 Two significant interactions of storage temperature and damage type, and of sap sample

and damage type on severe skin browning incidence (%) (n = 3 individual fruit

replicates comprising 4 sub-samples per fruit). ‗Honey Gold‘ mango fruit were

harvested from Northern Territory in the 2013 – 14 season. Different sap sample of 100

µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl of

terpinolene and 100 µl of distilled water was applied to small areas of the fruit abraded

with sand paper or peeled with peeler or cut with a scalpel blade. The fruit were then

held in either 12 or 20°C room at 90 – 100% RH for eight days and all fruit were moved

to a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for

incidence are expressed as mean and those followed by the same letters are not

signficant. ...................................................................................................................... 203

Table 7.2 Two significant interactions of sap sample and storage temperature, and of sap sample

and damage type on severe skin browning severity (cm2 affected) (n = 3 individual fruit

replicates comprising 4 sub-samples per fruit). ‗Honey Gold‘ fruit were harvested from

xxviii

Northern Territory in the 2013 – 14 season. Different sap sample of 100 µl aliquots of

morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and

100 µl of distilled water was applied to small areas of the fruit abraded with sand paper

or peeled with peeler or cut with a scalpel blade. The fruit were then held in either 12 or

20°C room at 90 – 100% RH for eight days and all fruit were moved to a ripening room

at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for severity are

expressed as mean and the significant difference between the treatments when the

difference of them is ≥ the data of LSD. ..................................................................... 205

Table 7.3 Significant effect of storage temperature and a significant interaction of sap sample and

damage type on mild skin browning incidence (%) (n = 3 individual fruit replicates

comprising 4 sub-samples per fruit). ‗Honey Gold‘ mango fruit were harvested from the


morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and

100 µl of distilled water was applied to small areas of the fruit abraded with sand paper

or peeled with peeler or cut with a scalpel blade. The fruit were then held in either 12 or

20°C at 90 – 100% RH for eight days and all fruit were moved to a ripening room at

20°C and 90 – 100% RH until fruit reached eating ripe. Data for incidence are

expressed as mean and those followed by the same letters are not significant. ............ 207

Table 7.4 A significant interaction of damage type and sap sample on mild skin browning severity

(cm2

affected) (n = 3 individual fruit replicates comprising 4 sub-samples per fruit).

‗Honey Gold‘ fruit were harvested from Northern Territory in the 2013 – 14 season.

Different sap sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of

their upper-phase, 50 µl of terpinolene and 100 µl of distilled water was applied to small

areas of the fruit abraded with sand paper or peeled with peeler or cut with a scalpel

blade. The fruit were then held in either 12 or 20°C at 90 – 100% RH for eight days and

all fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe. Data for severity are expressed as mean and the significant difference

between the treatments when the difference of them is ≥ the data of LSD. ................ 208

Table 7.5 Effect of storage temperature and a significant interaction of sap sample and damage type

on total skin browning incidence (%) (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ fruit were harvested from Northern Territory in the

2013 – 14 season. Different sap sample of 100 µl aliquots of morning and afternoon

spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and 100 µl of distilled water

was applied to small areas of the fruit abraded with sand paper or peeled with peeler or

cut with a scalpel blade. The fruit were then held in either 12 or 20°C at 90 – 100% RH

xxix

for eight days and all fruit were moved to a ripening room at 20°C and 90 – 100% RH

until fruit reached eating ripe. Data for incidence are expressed as mean and those

followed by the same letters are not significant. ........................................................... 210

Table 7.6 A significant interaction of sap sample, damage type and storage temperature on total skin

browning severity (cm2 affected) (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ fruit were harvested from the Northern Territory in the

2013 – 14 season. Different sap sample of 100 µl aliquots of morning and afternoon

spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and 100 µl of distilled water

were applied to small areas of the fruit abraded with sand paper or peeled with peeler or

cut with a scalpel blade. The fruit were then held in either 12 or 20oC at 90 – 100% RH

for eight days and all fruit were moved to a ripening room at 20oC and 90 – 100% RH

until fruit reached eating ripe. Data for severity are expressed as mean and the

significant difference between the treatments when the difference of them is ≥ the data

of LSD. .......................................................................................................................... 212

Table 7.7 Effects of storage temperature on incidence (%) of mild, severe and total skin browning

of abraded fruit (n = 3 individual fruit replicates comprising 4 sub-samples per fruit for

morning and afternoon spurt sap, terpinolene; n = 3 individual fruit replicates

comprising 1 sub-sample per fruit for upper-phase morning and afternoon spurt sap).

The fruit were harvested from Northern Territory in the 2014 – 15 season. Different sap

sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-

phase and 50 µl of terpinolene were applied to small areas of the fruit abraded with sand

paper or peeled with peeler or cut with a scalpel blade. The fruit were then held in either

12 or 20°C at 90 – 100% RH for eight days and all fruit were moved to a ripening room

at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for incidence are


Table 7.8 Effects on total, severe and mild skin browning severity (cm2 affected) on abraded fruit

treated with different sap sample and kept at 12 or 20°C (n = 3 individual fruit replicates

comprising 4 sub-samples per fruit for morning and afternoon spurt sap, terpinolene; n

= 3 individual fruit replicates comprising 1 sub-sample per fruit for upper-phase

morning and afternoon spurt sap). ‗Honey Gold‘ mango fruit were harvested from


morning and afternoon spurt sap, 100 µl of their upper-phase and 50 µl of terpinolene

were applied to small areas of the fruit abraded with sand paper or peeled with peeler or

cut with a scalpel blade. The fruit were then held in either 12 or 20°C at 90 – 100% RH

for eight days and all fruit were moved to a ripening room at 20°C and 90 – 100% RH

xxx

until fruit reached eating ripe. Data for incidence are expressed as mean which

calculated by the number affected with severe skin browning divided by total number.

Data for severity are expressed as mean and those followed by the same letters are not

significant. ..................................................................................................................... 216

Table 7.9 Effect on the incidence (%) of the abraded position treated with different volumes of

terpinolene kept at 12 and 20°C (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ mango fruit were harvested from Northern Territory in

the 2013 – 14 season. Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl

terpinolene) were applied to small areas of the fruit that were abraded with sand paper

or peeled with peeler or cutted with scalpel. All fruit were then kept in different rooms

(12 and 20°C) at 90 – 100% RH for eight days and all fruit were moved to a ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data of incidence were

expressed as mean which calculated by the number affected with mild skin browning

divided by total number. Data of severity are expressed as mean and those followed by

the same letters are not significant. ............................................................................... 218

Table 7.10 Effect on the severity (cm2 affected) of the abraded position treated with different

volumes of terpinolene kept at 12 and 20°C (n = 3 individual fruit replicates comprising

4 sub-samples per fruit). ‗Honey Gold‘ mango fruit were harvested from Northern

Territory in the 2013 – 14 season. Different volumes of terpinolene (3.1, 6.3, 12.5, 25,

50 and 100 μl terpinolene, and distilled water) were applied to small areas of the fruit

that were abraded with sand paper or peeled with peeler or cutted with scalpel. All fruit

were then kept in different rooms (12 and 20°C) at 90 – 100% RH for eight days and all

fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe. Data of incidence were expressed as mean which calculated by the number

affected with mild skin browning divided by total number. Data of severity are


xxxi

List of Abbreviations Used in the Thesis

% Percent

± Plus or minus

® Registered trademark

Degree

AA Ascorbate acid

AUSB Abrasion under-skin browning (under-skin browning occurs surrounding the abrasion

position)

CA Calcium ascorbate

Ca Calcium

CI Chilling injury

cm centimeter

Co Cobalt

CO2 Carbon dioxide

DW Distilled water

e.g. For example

et al. And others

EUSB Extra under-skin browning (under-skin browning away from the abrasion position)

FW Frozen skin tissue weight

Gamma

Gy Gray

h Hour

kg kilogram

kGy Kilo Gray

kN Kilo Newton

LD Lenticel discolouration

LSD Least significant difference

mg Miligram

min Minute

mM mmol / L

N Newton

na Not statistical analysed

NS Not significant

O2 Oxygen

xxxii

PAL Phenylalanine ammonia-lyase

PE Pectin esterase

PG polygalacturonase

POD Peroxidase

PPO Polyphenol oxidase

RH Relative humidity

s Second

TA Titratable acidity

SSC Soluble solids concentration

TUSB Total under-skin browning (AUSB plus EUSB)

USB Under-skin browning

Viz. Namely

w / v Weight per volume

β Beta

μ Micro

1

Introduction Chapter 1

1.1 Mango

Mango belongs to the genus Mangifera from the Anacardiaceae family of flowering plants. The

genus Mangifera is comprised of various species, including Mangifera indica, Mangifera gedebe,

Mangifera minor and Mangifera mucronulate (Bally, 2006). Most commercially traded mango fruit

belong to Mangifera indica (Bally, 2006, Bally, 2009). This species originated in India. It was

traded and cultivated in neighbouring south-east Asia countries because of its pleasant appearance,

taste and aroma (Mukherjee, 1953, Mukherjee, 1972). Mangifera indica is currently commercially

grown in over 103 countries in tropical and sub-tropical regions of the world (Dillon et al., 2013).

1.1.1 Botany

The mango is a long-lived evergreen tree (Litz, 2009a). Cultivated mango trees typically grown to

between ~ 3 and 10 m tall. Wild non-cultivated seedling trees can reach ~ 15 to 30 m (Bally, 2006).

Mangoes are suitable for cultivation in tropical or sub-tropical regions (Litz, 2009b). The tree

generally has two to four major anchoring taproots that can reach to 6 m below ground level.

Fibrous finer roots extend to ~ 1 m under the ground (Bally, 2006). The leaves are oblong in shape

and vary from rounded to acuminate (Bally, 2006). They emerge green, turning tan-brown to purple

as they expand. When they mature, the colour of leaves changes to dark green (Bally, 2006).

Flowers are produced on terminal panicles with each flower consisting of five small white petals

that produce a mild sweet odour (Singh, 1960). Hermaphrodite and male mango flower forms are

found (Mukherjee and Litz, 2009).

Mango fruit typically take ~ 3 to 6 months to develop from a pollinated flower to the ripe fruit

(Singh, 1960, Knight and Schnell, 1994). Mango seed can be divided to monoembryonic and

polyembryonic. The monoembryonic axis is the true sexual cross and has one embryo.

Polyembryonic seed has more than one embryos of one is asexual in origin. The others are

genetically identical to the maternal parent (Bally, 2006). Mango fruit consist morphologically of

peel (skin), flesh (pulp) and seed. The fruit exhibit different shapes from round to ovate or oblong

depending on the cultivar (Campbell and Campbell, 1993, Mukherjee, 1976). As the fruit develop,

orange to red pigmented blush is manifested on the skin of fruit cheeks in association with exposure

to direct sunlight (Bally, 2006).

2

Figure 1.1 Images of A: a cultivated mango tree. B: mature mango fruit

1.1.2 Economic

Mango fruit are popular all over the world for their unique appearance, taste and aroma. They also

contain essential vitamins and nutrients beneficial for human health (Masibo and He, 2008). In 2010,

world production was ~ 35.9 million tonnes of mango fruit. India produced 46% of the total

production world production. China contributed ~ 12% of the total production (FAOSTAT, 2010).

Other production countries include Thailand, Pakistan, Mexico and Indonesia. Australia produces

just ~ 0.1% of world mango fruit production (AMIA, 2015).

Mango production in Australia is low by world measures. However, 53,500 tonnes to Australia

were contributed by Australia Agriculture (AMIA, 2015). Commercial mango production in

Australia is mostly confined to northern Australia. Mangoes are predominately cultivated in the

Northern Territory near Darwin, Katherine and Mataranka, in Western Australia near Kununurra

and Carnarvon, in North Queensland near Mareeba, the Burdekin and Bowen and in Central to

Southeast Queensland near Rockhampton, Bundaberg (Dirou, 2004). ‗Kensington Pride‘, also

known as the ‗Bowen‘, ‗B74‘ (CalypsoTM), ‗R2E2‘ and ‗Honey Gold‘ are the four most popular

cultivars in Australian commercial markets. ‗Kensington Pride‘ tree accounts for ~ 70% of the total

number of trees under cultivation in Australia (AMIA, 2014). ‗Palmer‘, ‗Keitt‘, ‗Kent‘, ‗Pearl‘ and

‗Brooks‘ cultivars are also produced in Australia, but in relatively low volumes (AMIA, 2014). The

mango summer season in Australia generally starts in September for Northern production regions

and ends in the following April for Southern production regions (Australian Mangoes;

A B

3

http://www.mangoes.net.au/buying_storage/availability.aspx). ‗Kensington Pride‘ and ‗B74‘

cultivars are harvested from September to March. The ‗Honey Gold‘ cultivar is harvested from

November to March. ‗R2E2‘ is harvested from November to February. ‗Keitt‘, ‗Kent‘ and ‗Palmer‘

cultivars are harvested from January to March. The cultivar ‗Pearl‘ is harvested from January to

February. Lastly, ‗Brooks‘ is harvested from February to April. Nowadays, Australian mango fruit

are successfully exported to markets that include Hong Kong, the United Arab Emirates, Singapore,

New Zealand and the UK / EU (AMIA, 2014).

1.2 Background

‗B74‘ (CalypsoTM) (Whiley, 2001) and ‗Honey Gold‘ (Dillon et al., 2013) are two recently bred

Australia mango cultivars (Figure 1.2 A and C). ‗B74‘ cultivar originated from a cross of

‗Kensington Pride‘ (an Australia cultivar) and ‗Sesation‘ (an American cultivar) (Hofman et al.,

2010). ‗Honey Gold‘ was from a cross of ‗Kensington Pride‘ and an unknown cultivar (Pinata

company, Pers. Comm.). ‗B74‘ is popular because of its particularly firm fibreless flesh, sweet

flavour and smooth orange blushed skin (AMIA, 2014). It currently represents ~ 20% of Australia‘s

total mango production and its‘ fruit are available from October to March (Dillon et al., 2013).

‗Honey Gold‘ mango is popular for its firm and juicy flesh, rich sweet flavour and brilliant golden

apricot-yellow colour. This fruit is available from November to March (AMIA, 2014).

Mature and harvested mango fruit are susceptible to pest and disease-causing organisms. Thus, they

have a short postharvest life and are subject to potentially severe losses during storage and transport

(Brecht and Yahia, 2009). γ-Irradiation has received approval in some jurisdictions for use as a

phytosanitarty insect disinfestation treatments on mango fruits prior to export to countries, such as

China (Thayer and Rajkowski, 1999, Arvanitoyannis et al., 2009, Morehouse and Komolprasert,

2004). However, discolouration of fruit lenticels, the macro pores that facilitate gas exchange

through the fruit skin, can be markedly exacerbated by γ-irradiation treatment. This is a major

problem for ‗B74‘ mango fruit that markedly adversely influences fruit quality (Hofman et al.,

2009). Fruit with pronounced lenticel discolouration (LD) (Figure 1.2 B) are unacceptable to

consumers, consequently depreciating the economic value of the fruit (Bezuidenhout, 2005). With a

view to reduce this disorder, the studies of underlying biological mechanisms regulating its

expression are important (Joyce et al., 2011).

Under-skin browning (USB) (Figure 1.2 D) is a peel discolouration disorder of ‗Honey Gold‘

mango fruit expressed as fruit ripen during or following freighting from production areas. It is

http://www.mangoes.net.au/buying_storage/availability.aspx

4

manifested as a brown-grey bruise-like lesion involving cells below the epidermis (Hofman et al.,

2009). Fruit skin abrasion has been used as a test means to induce USB (Hofman et al., 2009).

Starch is accumulated beneath the skin of mango fruit afflicted by USB (Marques et al., 2012).

1.3 Research Hypothesis

For LD and its worsening upon γ-irradiation, the working proposition was that it is the result of

enzymatic browning reactions. Therefore, it was hypothesised that postharvest treatments of mango

fruit with anti-browning chemicals, by bagging and by waxing to reduce stress would reduce

enzymatic browning (Figure 1.3). Ascorbic acid reduces coloured o-quinones to colourless di-

phenol (Gill et al., 1998) and citric acid inhibits PPO activity (Guerrero-Beltrán et al., 2005) (see

Chapter 3). Ca2+

of calcium ascorbate and of calcium chloride may maintain cell wall and

membrane structure to reduce enzymatic browning (Fan et al., 2005) (Chapter 3). Atmosphere

modification by waxing and bagging may reduce LD by limiting oxidative O2 entry into fruit

Figure 1.2 Images of A: ‗B74‘ mango fruit displaying LD; B: LD close up on ‗B74‘ mango fruit; C:

‗Honey Gold‘ mango fruit exhibiting under-skin browning; D: USB close up on ‗Honey Gold‘

mango fruit.

A B

C D

5

through lenticels and limit oxidative enzymes activities and total phenolics level (Chapters 3 and 4).

It was also proposed that different levels of PPO and / or POD activity and / or total phenolics

concentration at various fruit development stages would affect LD expression after γ-irradiation

(Chapter 4).

Two main alternative or potentially complimentary hypothesises relating to the mechanism of USB

were addressed (Figure 1.4). Hypothesis 1 was that exposure to low temperature induced chilling

injury involving enzymatic browning that expressed as USB (Chapter 5). Hypothesis 2 was that

mango sap in resin ducts adjacent to or in positions mechanically damaged by abrasion and / or

vibration caused USB which was intensified by low temperature (see Chapter 6 and 7).

Figure 1.3 A diagrammatic interaction model for proposed ameliorative effects of postharvest

treatments with anti-browning chemicals, waxing, bagging and fruit ripeness stages in reducing LD

induced by γ-irradiation.

6

Figure 1.4 Two potentially interacting models for USB induction whereby hypothesis 1 suggests

that USB involves a ‗typical‘ chilling injury process and hypothesis 2 suggests that mango sap from

resin / latex canals (laticifers) in the fruit is involved in USB initiated by physical damage and

exacerbated by low temperature.

1.4 Objectives

Part A. LD on ‗B74‘ mango fruit

Research was aimed at understanding the mechanisms involved in regulating LD on ‗B74‘ mango

fruit and at finding postharvest treatments that reduced LD.

The specific objectives were as follows:

a. Develop and evaluate postharvest treatments to reduce LD after γ-irradiation

b. Characterise biochemical changes (viz., PPO and POD activities, and total phenolics

concentration) in the fruit skin in response to postharvest treatments

Part B. USB on ‗Honey Gold‘ mango fruit

Research was aimed at finding the causes of USB and understanding the mechanism in terms of

‗Honey Gold‘ mango fruit skin biochemistry.

The specific objectives were as follows:

a. Characterise fruit growing region, physical stress (viz., abrasion and vibration) and storage

temperature factors related to USB on ‗Honey Gold‘ mango fruit.

7

b. Characterise biochemical changes (viz., PPO and POD activities and total phenolics

concentration) in fruit skin with versus without USB in response to postharvest treatments.

c. Characterise browning caused by sap and by the sap component terpinolene as at anatomical level.

1.5 Thesis Composition

This current Chapter overviews the thesis focus and its research aims. Chapter 2 reviews the

literature on causes of skin browning and treatments to reduce this disorder in fruits. Chapter 3

examines the effects of postharvest anti-browning chemicals, waxing, bagging and fruit ripeness

stage treatments on reducing LD induced by γ-irradiation. Chapter 4 studies the changes in PPO and

POD activities and in total phenolics concentration towards better understanding demonstrated

ameliorative effects of postharvest bagging treatments and fruit ripeness stage treatments in

reducing LD. LD structure was concomitantly characterised to further appreciate the mechanism/s.

Chapter 5 examines whether USB is typically chilling injury. Chapter 6 investigates the effects of

vibration plus low temperature on USB expression, and also the browning biochemistry. Chapter 7

examines the effects of mango sap and low temperature in inducing severe skin browning

symptoms similar to USB and also the anatomical characteristics of severe skin browning and USB.

Chapter 8 presents discussion and conclusion for the preceding research chapters and suggests

future directions for work to reduce LD and USB in commercial practice.

References

Australian Mangoes. http://www.mangoes.net.au/buying_storage/availability.aspx

[AMIA] Australian Mango Industry Association. 2014.

http://industry.mangoes.net.au/?PageID=112. [Online].

Arvanitoyannis, I. S., Stratakos, A. C. and Tsarouhas, P. 2009. Irradiation applications in vegetables

and fruits: a review. Critical Reviews in Food Science and Nutrition, 49: 427-462.

Bally, I. S. 2006. Species Profiles for Pacific Island Agroforestry. In ‗Mangifera indica (Mango)‘,

pp. 1-25. Permanent Agriculture Resources, Hōlualoa, Hawaii.

Bally, I. S. E. 2009. Australian national mango genebank. In ‗The 14th Australasian Plant Breeding

Conference and 11th Society for the Advancement of Breeding Research in Asia and

Oceania (SABRAO) Congress‘, Cairns, Australia.

Bezuidenhout, J. L. J. 2005. Anatomical investigation of lenticel development and subsequent

discolouration of ‗Tommy Atkins‘ and ‗Keitt‘ mango (Mangifera indica L.) fruit. Journal of

Horticultural Science and Biotechnology, 80: 18-22.

8

Brecht, J. K. and Yahia, E. M. 2009. Postharvest physiology. In ‗The Mango: Botany, Production

and Uses‘ (Litz, R. E. ed), pp. 484-528. CAB International, Wallingford, UK.

Campbell, R. J. and Campbell, C. W. 1993. Commercial Florida mango cultivars. Acta

Horticulturae, 341: 55-59.

Dillon, N. L., Bally, I. S. E., Wright, C. L., Hucks, L., Innes, D. J. and Dietzgen, R. G. 2013.

Genetic diversity of the Australian national mango genebank. Scientia Horticulturae, 150:

213-226.

Dirou, J. 2004. Mango growing.

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/119787/mango-growing.pdf

[online].

Fan, X., Niemera, B. A., Mattheis, J. E., Zhuang, H. and Olson, D. W. 2005. Quality of fresh-cut

apple slices as affected by low-dose ionizing radiation and calcium ascorbate treatment.

Journal of Food Science, 70: 143-148.

FAOSTAT. 2013. http://faostat.fao.org/.

Guerrero-Beltrán, J. A., Swanson, B. G. and Barbosa-Cánovas, G. V. 2005. Inhibition of

polyphenoloxidase in mango puree with 4-hexylresorcinol, cysteine and ascorbic acid. LWT

- Food Science and Technology, 38: 625-630.

Gil, M. I., Gorny, J. R. and Kader, A. A. 1998. Responses of ‗Fuji‘ apple slices to ascorbic acid

treatments and low-oxygen atmospheres. HortScience, 33: 305-309.

Hofman, P. J., Marques, J. R., Taylor, L. M., Stubbings, B. A., Ledger, S. N. and Jordan, R. A.

2009. Skin damage to two new mango cultivars during irradiation and cold storage. Acta


Hofman, P. J., Marques, J. R., Taylor, A. H., Stubbings, B. A., Ledger, S. N. and Jordan, R. A.

2010. Devlopment of best practice pre- and postharvest of ‗B74‘ mango fruit: Phase II. Final

report MG06005. Horticulture Australia Ltd., Sydney, Australia.

Joyce, D., Hofman, P., Marques, R., Nguyen, T. and Gupta, M. 2011. Lenticel damage on ‗Calypso‘

mango. In ‗Conference on Horticulture for the Future‘, pp. 18-19.

Knight, R. J., Jr. and Schnell, R. J. 1994. Mango introduction in Florida and the ‗Haden‘ cultivar‘s

significance to the modern industry. Economic Botany, 48: 139-145.

Litz, R. E. 2009a. Mango. part 5. transgenic tropical and subtropical fruits and nuts. Compendium

of Transgenic Crop Plants. 6: 163-174.

Litz, R. E. 2009b. Introduction: botany and importance. In ‗The Mango: Botany, Production and

Uses (2nd)‘ (Litz, R. E. ed), pp. 1-11. CAB international, Wallingford, UK.

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9

Marques, J. R., Hofman, P. J., Giles, J. E. and Campbell, P. R. 2012. Reducing the incidence of

under-skin browning in ‗Honey Gold‘ mango (Mangifera indica L.) fruit. Journal of

Horticultural Science and Biotechnoloty, 87: 341-346.

Masibo, M. and He, Q. 2008. Major mango polyphenols and their potential significance to human

health. Comprehensive Reviews in Food Science and Food Safety, 7: 309-319.

Morehouse Kim, M. and Komolprasert, V. 2004. Irradiation of food and packaging: an overview. In

‗Irradiation of Food and Packaging‘ (Morehouse, K. M. and Komolprasert, V. eds), pp. 1-

11. American Chemical Society, Washington, USA.

Mukherjee, S. K. and Litz, R. E. 2009. Introduction: botany and importance. In ‗The Mango:

Botany, Production and Uses‘ (Litz, R. E. ed.), pp. 1-18. CAB international, Wallingford,

UK.

Mukherjee, S. K. 1953. The mango: its botany, cultivation, uses and future improvement, especially

as observed in India. Economic Botany, 7: 130-162.

Mukherjee, S. K. 1972. Origin of mango (Mangifera indica). Economic Botany, 26: 260-264.

Mukherjee, S. K. 1976. Current advances on mango research around the world. Acta Horticulturae,

57: 37-42.

Singh, L. B. 1960. The mango. In ‗The Mango‘, pp. xiii and 438. Leonard Hill Books Ltd., London,

UK.

Thayer, D. W. and Rajkowski, K. T. 1999. Developments in irradiation of fresh fruits and

vegetables. Food Technology, 53: 62-65.

Whiley, A. 2001. Mango (Mangifera indica) ‗B74‘. Plant Varieties Journal, 14: 45-46.

10

Literature Review Chapter 2

2.1 Skin Browning Disorders of Harvested Produce

2.1.1 Symptoms

Browning disorders on harvested produce are cosmetic features that adversely influence the

purchasing decisions of consumers. Skin browning disorders are seen on the surfaces of many fruits

including litchi (Jiang and Fu, 1998), peaches and nectarines (Cheng and Crisosto, 1994, Cheng and

Crisosto, 1995), pears (Guan et al., 2006) and table grapes (Vial et al., 2005).

2.1.2 Mechanism of browning in fruit

2.1.2.1 Enzymatic browning

Most browning disorders of fruits and vegetables are catalysed by enzymes. The most common

biochemical browning process involves the reaction of polyphenol oxidase (PPO) and / or

peroxidase (POD) enzymes with phenolic substrates in the presence of oxygen (Figure 2.1, Oren-

Shamir, 2009). Factors limiting enzymatic browning include the concentration of phenolics (Rocha

and Morais, 2002, Prohens et al., 2007), the activity of PPO and POD enzymes, and levels of

antioxidants, such as L-ascorbic acid. Anthocyanins can also be the substrates for PPO, such as in

litchi fruit browning (Figure 2.1, Oren-Shamir, 2009, Jiang et al., 2004). The phenylalanine

ammonia-lyase (PAL) enzyme can also be involved in enzymatic browning through the synthesis of

phenolic compounds under external stress (Figure 2.2, Saltveit, 2000). Disruption of cell integrity is

always associated with the onset of enzymatic browning.

11

Figure 2.1 Proposed mechanism of phenolics‘ degradation and tissue browning in fruits (Oren-

Shamir, 2009)

Figure 2.2 Metabolism associated with browning induced by wounding (Saltveit, 2000)

Enzymes

Polyphenol oxidases

12

PPOs consist of a group of copper-containing enzymes which are also known as catechol oxidase,

catecholase, diphenol oxidase, o-diphenolase, phenolase and tyrosinase (Martinez and Whitaker,

1995). PPOs are mostly located in plastids (Guo et al., 2009, Queiroz et al., 2011) including

chloroplasts (Mayer, 2006) and other sub-cellular organelles, such as mitochondria (Matheis et al.,

1983). PPOs are widely distributed in the microbial, animal and plant kingdoms (Tomás-Barberán

and Espín, 2001). They play a significant role in enzymatic browning processes. PPOs generally

first hydrolyse the monophenols to o-diphenols which then oxidise to o-quinones. The o-quinoes

condense to form brown melanin pigments (Oren-Shamir, 2009). An anthocyanase-anthocyanin-

phenolic-PPO activity reaction has been suggested as the mechanism of skin browning of litchi fruit

(Jiang et al., 2004). Based on their ability to oxidise specific phenolic substrates in the presence of

molecular oxygen, PPOs are divided into monophenol oxidases, o-diphenol oxidases and multi-

copper oxidases (Aniszewski, 2008).

Peroxidases

PODs are a group of enzymes which can also be involved in enzymatic browning reactions (Nicolas

et al., 1994, Oren-Shamir, 2009). They are located mainly plastids, including chloroplasts and the

cell walls in plants (Passardi et al., 2004). They perform single-electron oxidation on a wide of

compounds in the presence of hydrogen peroxide. PODs involved in enzymatic browning may

make use of hydrogen peroxide produced in a PPOs-catalysed reaction (Tomás-Barberán and Espín,

2001).

Phenylalanine ammonia-lyase (PAL)

PAL is the first enzyme in the phenylpropanoid pathway. It plays a key regulatory role in the

synthesis of phenolic compounds in plants (Pina and Errea, 2008). These compounds can be further

converted to other phenolic compounds via coumarate. These phenolics, including the flavonols,

anthocyanins, chlorogenic acid and caffeic acid derivatives, are thought to serve as browning

substrates in some plant tissues (Tomás-Barberán et al., 1997, Saltveit, 2000). PAL is responsive to

stress such as wounding (Tomás-Barberán et al., 1997, Saltveit, 2000), low temperature (Sanchez-

Ballesta et al., 2000, Nguyen et al., 2003) and irradiation (Jan et al., 2012). The involvement of

PAL in enzymatic browning of tissue under wound stress has been proposed by Saltveit (2000)

(Figure 2.2).

13

Substrate

Phenolics are the primary substrates and oxygen is the ‗co-substrate‘ in the process of enzymatic

browning. Phenolics are divided into non-flavonoids (viz., phenolic acids and stilbenes) and

flavonoids (viz., flavonols, flavones, flavonones, flavanols and anthocyanins) (Rinaldo et al., 2010).

They are characteristically located in the vacuole of higher plant cells and are distributed within

most tissues. While phenolics act as substrates involved in enzymatic browning (Cheynier, 2005),

others are antioxidants that help to provide protection from free radical damage (Robards et al.,

1999). The levels of phenolics help modulate the rate of enzymatic browning (Rocha and Morais,

2002, Prohens et al., 2007). As explained above, monophenols are oxidized to di-phenol and then

further oxidized to o-quinones under oxygen. The degradation of anthocyanin acts as a browning

process in litchi pericarp via the anthocyanin-PPO-phenol system (Jiang, 2000, Zhang et al., 2001).

Chlorogenic acid (Cheng and Crisosto, 1995) and (-)-epiccatechin (Liu et al., 2010) levels have

been positively correlated with browning in peaches, nectarines and litchi pericarp.

2.1.2.2 Non-enzymatic browning

Non-enzymatic browning (NEB) is a process promoted by heat, resulting in brown, dark or red

melanin without the involvement of enzymes. Non-enzymatic browning has been studied in fruits

such as pear puree (Ibarz et al., 1999), peach puree (Garza et al., 1999) and pineapple juice

(Rattanathanalerk et al., 2005). The maillard reaction (carbonyl-amino reaction), caramelisation

(non-amino carbonyl reaction, chemical oxidation of ascorbic acid and maderisation are four forms

of non-enzymatic browning (Ibarz et al., 2000, Manzocco et al., 2000). The maillard reaction, one

typical non-enzymatic browning, is a reaction between reducing sugars and amino-acids (Martins et

al., 2000). The reactive carbonyl group of the sugar reacts with the free amino group to produce a

condensation product of N-substitued glycosilamine, which rearranges to form an Amadori product

(Martins et al., 2000). The subsequent degradation of the Amadori product is dependent on the pH

of the system (Figure 2.3). Caramelisation is an another type of non-enzymatic browning that

involves pyrolosis of sucrose, which is different from the Maillard reaction (Quintas et al., 2010).

Degradiation of L-Ascorbic acid produces reactive carbonyl compounds and undergoes further

reactions leading to the formation of brown pigments (Roig et al., 1999). Maderisation is one non-

enzymatic form between the heating and oxidisation of wine (Eichner and Ciner-Dorux, 1981).

14

Figure 2.3 Maillard reaction scheme adapted from Hodge (1953)

2.2 Mango Skin Browning Disorders

Mango fruit have a relatively short postharvest life at ambient temperature (Sivakumar et al., 2011).

Their high metabolic activity, sensitivity to pathogen attack and responsiveness to surrounding

environments result in economic loss (Sivakumar et al., 2011). Skin browning occurs in the supply

chain and is influenced by orchard, harvesting and postharvest practices (Sivakumar et al., 2011).

The later include postharvest treatments, packing operations, temperature management,

transportation and storage conditions (Sivakumar et al., 2011, Singh et al., 2013). Disorders on

mango fruit expressed as skin browning result from mechanical damage, chilling injury (CI), heat

damage, sapburn, anthracnose, stem end rot and black spot (Figure 2.4, Sivakumar et al., 2011,

Singh et al., 2013). Lenticel discolouration (LD) is a common browning disorder focused on

lenticels and / or immediately surrounding areas of the mango fruit skin (Hofman et al., 2009).

Under-skin browning (USB) is a less common browning disorder focused in sub-epidermal cells

(Hofman et al., 2009).

http://www.sciencedirect.com/science/article/pii/S092422440100022X

15

Figure 2.4 Images showing symptoms of handling issues affecting mango fruit. A: Brushing

damage (from DPI, Queensland; http://postharvest.ucdavis.edu/PFfruits/MangoPhotos); B:

Compression damage (from DPI, Queensland;

http://postharvest.ucdavis.edu/PFfruits/MangoPhotos); C: CI (from Edwards, Don University of

California, Davis; http://postharvest.ucdavis.edu/PFfruits/MangoPhotos ); D: Sapburn (from DPI,

Queensland; http://postharvest.ucdavis.edu/PFfruits/MangoPhotos).

2.2.1 Causes

2.2.1.1 Physical

Handling, packaging and transportation

Mechanical damage is a major contributor to postharvest loss through the chain from harvest

through packing shed and wholesaler to retailer (Sivakumar et al., 2011). Impact damage often

occurs during fruit harvest, selection, manipulation, and transportation (Sivakumar et al., 2011). It

can involve the impact with other fruit and with containers or machinery (Sivakumar et al., 2011).

B A

D C

http://postharvest.ucdavis.edu/PFfruits/MangoPhotos




http://ucanr.edu/repository/fileaccess.cfm?article=83443&p= ZQJFMV

http://ucanr.edu/repository/fileaccess.cfm?article=83449&p= NLYYQB

http://ucanr.edu/repository/fileaccess.cfm?article=83456&p= JIJXCO






















16

Compression damage is associated with loads during packing and in storage (Martinez-Romero et

al., 2004). Puncture and vibration damage are other mechanical injuries, the later especially during

transportation (Sivakumar et al., 2011). A loosely associated issue is that fresh-cut preparation, such

as by peeling or cutting also causes browning.

Field handling issues including abrasion caused by stems and harsh packing-house procedures such

as brushing (Figure 2.4 A), can damage fruit. Compression from the upper fibreboard tray (Figure

2.4 C) and vibration during transportation caused skin browning (Kader, 2002). Threshold

compression values which damage cells of ‗Carabao‘ mango fruit were 0.8 kN at green mature, 0.2

kN at colour break and 0.05 kN at 30% yellow peel colour stages (Valerio et al., 2000). During

distribution of ‗Nam Dokmai‘ mango fruit, a 5 cm height was found to be a safe drop height for

fruit within corrugated fibreboard boxes and reusable plastic containers (Chonhenchob and Singh,

2003).

17

Table 2.1 Problem, causes and class of mango fruit disorders associated with skin browning

Problem Cause/s Class Author

Mechanical damage Abrasion, brush or compression or wind Physical Kader (2002)

Heat damage Heat treatment Joyce and Shorter (1994), Jacobi et al.

(2001a)

CI Low temperature Wang et al. (2008), Chidtragool et al. (2011)

Others ɣ- irradiation Thomas and Janave (1973)

Sapburn (also sap

injury)

Mango sap (latex) Chemicals Robinson et al. (1993)

Others detergent Bally et al. (1996)

Stem end rots Fungal pathogens: Dothiorella dominicana, Dothiorella

mangiferae, Lasiodiplodia theobromae (Syn. Diplodia

natalensis Phomopsis mangiferae, Cytosphaera

mangiferae, Pestalotiopsis sp. and Dothiorella‗long‘

Biological Johnson et al. (1992)

Anthracnose Fungal pathogens: Colletotrichum gloeosporioides

Penz.).

Fitzell and Peak (1984)

Alternaria black spot Fungal pathogens: Alternaria alternata Biological

Prusky et al. (1993), Prusky et al. (2006)

Others Fruit flies: Bactrocera tryoni (Queensland fruit fly) and

Ceratitis captitata (Mediterranean fruit fly)

Heather et al. (1997)

18

Apple-to-apple impact caused bruising damage (Pang et al., 1992). Compression forces ranging

from 9 to 21 N in the box used for transportation caused damage on tomatoes (Silva, 1992).

Compression of Asian pear fruit with a 20-mm diameter steel sphere to 25 N force to achieve 1.5

and 3.0 mm deformation caused bruising (Chen, 1987). Vibration during transportation or simulated

vibration caused mechanical damage on ‗Huanghua‘ pear (Zhou et al., 2007), ‗Abate‘ pear

(Berardinelli et al., 2005) and ‗Solo‘ papaya (Quintana and Paull, 1993) fruits.

Browning of plant tissues typically results from membrane disruption which leads to PPO mixing

with phenolic compounds (Kader, 2002). PAL is suggested to be involved in tissue browning by

synthesising phenolic compounds that can act as substrates for enzymatic browning (Saltveit, 2000).

Meanwhile, accumulation of H2O2 in association with tissue wounding followed by the increase of

PAL contributes to the destruction of cell membrane integrity, resulting in browning in apple fruit

(Su et al., 2011). In addition, physical damage can increase the rates of respiration, ethylene

production, membrane lipid degradation, water loss and accumulation of secondary metabolites at

the damage site (Watada et al., 1996).

Aside from brusing per se, improper handling increases other disorders including LD and USB of

mango fruit (Rymbai et al., 2012). LD is manifested on mango fruit that are harvested wet

(Duvenhage, 1993). That is, humid or wet conditions on the harvest day are associated with a high

incidence of post-storage LD (Oosthuyse, 2002). Similarly, Everett et al. (2008) found increased

LD on ‗Hass‘ avocado fruit after 2 h of imbibing water. Among operations, brushing of mango fruit

was found to contribute the most damage to lenticels, followed by soap washing and hydro-heating

(Oosthuyse, 2000). With USB of ‗Honey Gold‘ mango fruit, long transportation increased this

disorder (Hofman et al., 2009).

Sites of physical damage can become openings for fruit pathogen entry (Prusky et al., 2006). High

relative humidity and warm temperature are the preferred conditions for disease progression

(Sivakumar et al., 2011).

Low temperature

Exposure to low, non-freezing temperatures is routinely utilised commercially to prolong the

storage life of many fruits (Kader, 2002). However, maintaining fruits at low temperature for

prolonged periods can cause CI in selected harvested fruits. These include mangoes (Chidtragool et

19

al., 2011), peaches (Lurie and Crisosto, 2005), plums (Luo et al., 2011), loquats (Cao et al., 2009),

pomegranates (Barman et al., 2011) and bananas (Pongprasert et al., 2011).

The critical temperature for CI in mango fruit is ~ 12 – 13°C (González-Aguilar et al., 2001).

Mango fruit can show red and green LD when stored at 12°C (Aharoni et al., 2000, Feygenberg et

al., 2004). Skin browning can also occur when mango fruit are stored below ~ 12 – 13°C but above

the freezing point (Wang et al., 2008). Skin browning is a common symptom of CI (Pesis et al.,

2000, Phakawatmongkol et al., 2004). CI symptoms developed on ‗Kent‘ mango fruit during

storage at 5 or 10°C for 14 days (González-Aguilar et al., 2001) and on ‗Nam Dok Mai‘ mango fruit

during storage at 4ºC for 30 days (Chidtragool et al., 2011). PAL activity in mango fruit skin is

suggested to be closely related to browning induced by low temperature (Chidtragool et al., 2011).

Expression of CI symptoms increases after the fruit are moved from low temperature to ambient

temperature. For example, it became obvious on green mature ‗Kensington‘ mango fruit after the

fruit were moved to 20°C following low temperature (1 or 5ºC) storage for one week (Chaplin et al.,

1989) and after one day on ‗Zihua‘ mango fruit moved to 25°C from 2°C for ten days (Zhao et al.,

2009). Duration of exposure to low temperature was found to be related to chilling injury with

greater CI injury for longer storage periods (Saltveit and Morris, 1990).

Fruit maturity and cultivar are the factors related to the susceptibility to CI. ‗Haden‘ mango fruit

can be stored at 1.7°C for 4 weeks with no CI (Hatton, 1990). However, ‗Kent‘ mango fruit showed

CI during storage at 5 or 10°C for 14 days. Mature ‗Tommy Atkins‘ mango fruit had no CI

symptoms after 18 days storage at 5°C plus one or three days at conditions of 20°C as compared to

immature and half-mature ‗Tommy Atkins‘ mango fruit (Mohammed and Brecht, 2002). ‗Zihua‘

mango fruit at 45% – 55% yellow and at 10 – 20% preyellow were more tolerant to CI at 2°C for 12

days plus two days at 20°C than fruit at 100% green (Zhao et al., 2009). In that study, PPO activity

and phenolic compounds did not appear to directly contribute to CI development in fruit. Rather,

the authors suggested that membrane damage is the onset of CI and a higher antioxidant capacity is

involved in relative tolerance of tissues to low temperature. CI has also been reported to be

expressed as skin browning on ‗Luoyangqing‘ loquat fruit stored at the low temperature of 5°C.

Nguyen et al., (2003) reported that CI that occurred on ‗Kluai Khai‘ and ‗Kluai Hom Thong‘

banana fruit skins was related to relative changes in PAL and PPO activity and total phenolics

concentration rather than the absolute concentrations. An increase in membrane permeability,

evident as increased relative electrolyte leakage, can also be found in chilled banana peel (Jiang et

al., 2004).

20

It is evident from the literature that oxidative stress is an early response of horticultural produce to

CI at least partly because hydrogen peroxide accumulates and damages membranes. An increase in

the malondialdehyde content in ‗Tainong‘ mango fruit stored at low temperature (4°C) confirms

lipid peroxidation and disruption of membrane integrity (Wang et al., 2008).

ɣ- Irradiation

ɣ- Irradiation (from Co60

) is a phytosanitary treatment for harvested fruit (Bustos et al., 2004).

According to the World Health Organisation, Food & Agriculture Organisation and the Atomic

Energy Agency, irradiation of food with up to 10 kGy is safe. According to the USA Food and

Drug Administration (FDA), the allowed dosage for irradiation of fresh produce allowed is 1 kGy.

The USA has agreed to import irradiated mango fruit from India and Mexico (FDA, 1984). ɣ-

Irradiation with up to 600 Gy has been determined to reduce the incidence of disease such as

anthracnose on mango fruit (Johnson et al., 1990a). Using higher irradiation doses is more cost

effective to the growers than using lower doses. However, if higher irradiation doses are adopted,

the incidence of irradiation stress injury expressed as surface browning in mango fruit can be higher

(Sivakumar et al., 2011). Irradiation with 2 kGy caused skin browning on ‗Totapuri‘ mango fruit

(Thomas and Janave, 1973) and on ‗B74‘ mango fruit (Hofman et al., 2009b). Similar adverse

effects of ɣ- irradiation have been reported for potato tubers (Ogawa and Uritani, 1970) and banana

peel (Thomas and Nair, 1971). In the study, the increase of total phenolics concentration and POD

activity and a transient increase of o-diphenol oxidase activity were associated with irradiated

potato tuber browning (Ogawa and Uritani, 1970). A good correlation was found between PPO

activity and skin browning in irradiated banana fruit (Thomas and Nair, 1971). Irradiation with 2

kGy at 32 kGy / h induced browning on ‗Albidus‘ mushroom (Beaulieu et al., 2002). The authors

suggested that the irradiation-induced browning mechanism involved oxidative molecular oxygen in

the cell cytoplasm, and decompartmentation of phenolic compounds from the vacuole and mixing

with PPO. Irradiation with 3 kGy induced browning of cut ‗witloof chicory‘ by increasing the total

phenolics concentration and possibly also by increasing membrane permeability (Hanotel et al.,

1995). ɣ-Irradiation can induce free radicals that could damage cell-wall membrane and lead to fruit

softening (Kovacs and Keresztes, 2002). ɣ-Irradiation at ≥ 600 Gy caused severe LD on

‗Kensington Pride‘ mango fruit (Johnson et al., 1990b).

21

Heat treatment

Heat treatments are applied to harvested fruit to kill fruit flies and pathogens. They can also be used

to reduce CI. Three methods used to disinfect fruit including mango fruit, are vapour heat treatment

(VHT), forced hot-air treatment (FHAT) and hot water immersion treatment (HWT) (Jacobi et al.,

2001b). VHT is also called high humidity air heating. Vapour heat treatment as a VHT dis-

infestation protocol of mango fruit is accepted for exporting to Japan from the Philippines, Thailand

and Australia (Armstrong, 1996, Jacobi et al., 2001b). FHAT is also known as non-condensing air

heating. This technology, as developed in the United States for mango fruit (Mangan and Ingle,

1992), requires that relative humidity should be controlled carefully. It is commercially used as a

phytosanitory tool on papaya fruit grown in Hawaii and exported to the mainland United States, and

also for papaya fruit grown in the Cook Islands and exported to New Zealand (Armstrong, 1996).

With hot water immersion, the heat transfers from the water to the skin of the fruit and then to the

centre of the fruit. This method gives faster of heat transfer to the skin of the fruit than from the skin

to centre (Jacobi et al., 2001b). It has been used for litchi fruit (Jacobi et al., 1993).

Mechanistically, hot air treatment at 45°C for 3 h reduced disease on strawberry fruit by increasing

antioxidants capacities, such as ascorbate peroxidase and superoxide dismutase (Vicente et al.,

2006). Hot air at 36 – 60°C for 1 – 3 h reduced mould decay by increasing chitinase, β-1, 3-

glucanase, peroxidase and polyphenol oxidase enzymes and inhibiting spore germination, germ tube

elongation and mycelial growth. Based on the literature, heat treatment can have direct effects on

the slowing of gem tube elongation and / or of inactivating killing germinating spores so as to

reduce inoculum load and minimise rots. However, the indirect effects of increasing pathogenesis

related proteins, such as chitinase and β-1,3-glucanase, and antifungal-like defence enzymes, such

as PPO and / or POD, may also be important (Schirra et al., 2000).

Heat treatment used to reduce disease can also cause heat damage to plant tissues, including damage

on mango fruit (Ghasemnezhad et al., 2008). HWT at 42 – 48°C for 30 – 90 min induced skin

scalding on ‗Kensington‘, ‗Irwin‘, ‗Haden‘ and ‗Tommy Atkins‘ mango fruit (Smith and Chin,

1989). Furthermore, HWT at 48°C for 7.5 – 30 min caused skin scalding on ‗Kensington‘ mango

fruit (Jacobi and Wong, 1992). Miller et al. (1991) found that FHAT at 51.5°C for 125 min

increased peel pitting on ‗Tommy Atkins‘ mango fruit. VHT to a seed surface temperature at

47°Cfor 15 min caused browning on ‗Kensington‘ mango fruit (Jacobi and Giles, 1997). Joyce and

Shorter (1994) reported that HWT at 47°C for 2 h induced browning on ‗Kensington Pride‘ mango

fruit.

22

Postharvest handling treatments can also increase LD. A combination of hot water and hot air on

‗Kensington Pride‘ mango fruit (Jacobi et al., 1996), HWT at 46°C for 120 min or HWT at 49ºC for

60 min on ‗Tommy Atkins‘ mango fruit‘ (Jacobi et al., 2001b) and HWT 46°C for 90 min or HWT

at 49°C for 60 min on ‗Keitt‘ (Jacobi et al., 2001b) increased LD. While hot water dipping reduced

red LD, it increased black LD on ‗Tommy Atkins‘ mangoes from Northeast Brazil (Self et al.,

2006).

2.2.1.2 Chemicals

Chemical compounds in mango sap and exogenous detergents can induce sapburn. Sap and

exogenous detergents can also cause skin browning on mango fruit.

Sapburn or sap injury is a common disorder of mango fruit (Loveys et al., 1992). Mango plants

have an extensive system of ducts in both the fruit and stem (Joel, 1978, Joel, 1980 and Joel, 1981).

The sap contained in the fruit ducts can be deposited on the fruit surface during harvest operations

(Joel, 1978, Joel, 1980 and Joel, 1981). Damage caused to the skin where it comes in contact with

exuded sap is often expressed as dark, sunken lesions. Mango sap or latex can be separated into two

phases: upper-phase (yellow-brown, oily part) and lower-phase (milk liquid). Terpinolene has been

found to be the principal compound that damages membranes and causes browning (Loveys et al.,

1992). Terpinolene contributed 58% to the oily upper phase of the spurt sap from ‗Kensington Pride‘

mango fruit. Exposure of fruit to ≥ 1% synthesised terpinolene could cause sapburn (Loveys et al.,

1992). In addition, car-3-ene accounted for 59.1% in the oily upper phase of the spurt sap from

‗Irwin‘ mango fruit. The severity of sapburn has been reported to be closely related to the time of

harvesting.

Sap collected in the afternoon damaged more than the sap collected in the morning for ‗Samar

Bahisht Chaunsa‘ mango fruit (Maqbool, 2007). Fruit harvested in the morning suffered less

sapburn than fruit harvested in the afternoon (Maqbool, 2007, Amin et al., 2008). The authors

suggested that it is possibly because of the lower concentration of terpinolene in the morning sap

compared to the afternoon sap. Higher PPO activity was also found in sap from ripened fruit than

that from that of unripened fruit (Robinson et al., 1993). However, the mechanism of sapburn on

biochemistry was suggested to be an enzymatic browning involving catechol oxidase-type PPO

activity in fruit skin rather than laccase-type activity in sap (Robinson et al., 1993). Similar to

mango sapburn, oleocellosis on citrus fruit such as sweet oranges, lemons and limes is a effect of

the release of oil from peel oil glands that leaks to surrounding cells after mechanical damage

23

(Montero et al., 2012). Factors related to the occurrence of oleocellosis are: the composition of the

oil of the different cultivars and species of citrus fruit (Montero et al., 2012); weather conditions

during fruit harvesting and fruit ripeness (Alférez et al., 2000); fruit moisture (Zheng et al., 2010);

the season of fruit development, the position of fruit in the canopy and temperatures beyond 38°C

(Chikaizumi, 2000). This symptom is not consistent with a fruit nutrition disorder (Assimakopoulou

et al., 2009).

With regard to harvest and postharvest practices for mango fruit, washing fruit in ambient water

(O‘Hare et al., 1996) and washing fruit in one or several, disinfectants or soaps including Agral®

,

Cold Power® or Mango Wash

® (Bally et al., 1997) can reduce sapburn but may increase skin

browning as well as LD.

2.2.1.3 Biological

Pathogens and insect pests afflict mango fruit. The three predominant poshravest mango disease are:

anthracnose disease is caused by the fungal pathogen Colletotrichum gloeosporiodes (Fitzell and

Peak, 1984); stem end rots are caused by Dothiorella dominicana, Phomopsis spp., Botryodiplodia

theobromae, Lasiodiplodia theobromae (Johnson et al., 1992), and Phnomopsis mangiferae

(Davidzon et al., 2010); and alternaria black spot is caused by Alternaria alternata. Anthracnose is

charcterised by dark, sunken lesions on ripe fruit with pink slimy spore masses (Jeffries et al., 1990).

Stem end rot is manifested as a dark brown to black rot that starts at the stem end as a dark brown

ring and spreads through the fruit. Alkenylresorcinols (5-n-pentadecylresorcinol and 5-n-

heptadecenylresorcinol) in the mango fruit peel were associated with anthracnose resistance

(Hassan et al., 2007, Zainuri et al., 2010, Karunanayake et al., 2014) and at least partially explained

why some cultivars were more resistant to anthracnose. Levels of chitinase in mango skin may

account for the relative susceptibility of specific cultivars to stem end rots (Karunanayake et al.,

2014). As fruit became mature, they became more susceptible to disease. In the case of alternaria

black rot, relative humidity of fruit in the orchard ≥ 80% (Prusky et al., 1993) and warm ambient

temperatures (Sivakumar et al., 2011) increased the incidence of the disease.

Bactrocera tryoni, Queensland fruit fly, and Ceratitis captitata, Mediterranean fruit fly, are

common pests in Australia. Infestation by these flies induced browning for ‗Kensington Pride‘

mango fruit (Heather et al., 1997)

24

2.2.2 Treatments for controlling browning

2.2.2.1 Physical

Handling, packaging and transportation

As discussed above, sapburn, LD and mechanical damage are the issues during handing, packaging

and transportation.

As sapburn mainly occurs to mango fruit during harvest time, proper handling may efficiently

reduce this disorder. One method of harvesting is to pick mango fruit with long stems and transport

them to the packing shed in plastic crates (Holmes et al., 1992). The fruit are then de-sapped by

removing the stem and placing the fruit with their stem down on a conveyor or rack to drain for 20

or 30 min. De-sapping on the ground or on special de-sapping racks and trays by keeping the fruit

in an inverted position or on conveyor belts have also been reported to lessen sapburn on mango

fruit (Brown et al., 1986). Detergent dips and sprays prior to de-stemming, or de-stemming under a

lime solution, or picking without stems onto a harvesting aid with immediate dipping or

immediately spraying detergent onto the fruit reduced sapburn of ‗Kensington Pride‘ cultivar

(Holmes et al., 1992). According to Mazhar et al. (2011), harvesting mango fruit with 11 – 15 cm

long pedicels and then carefully de-stemming, de-sapping in 0.5% lime solution for 2 – 3 min and

washing in tap water reduced sapburn, stem rot and physical damage as compared to traditional

procedures. As noted above, the afternoon sap resulted in more severe damage than the morning sap,

although a greater volume of sap flew out in the morning than in the afternoon (Maqbool, 2007,

Amin et al., 2008). This being the case, morning harvests could reduce the problem.

With regard to physical injury, careful picking and not throwing fruit in conjuction with tidy

packaging could reduce mechanical damage. The use of foam nets can protect mango fruit from

mechanical damage during transportation (Chonhenchob and Singh, 2003).

With regard to reducing LD on mango fruit, drying the orchard soil to at least –50 kPa has been

reported to reduce LD on mango fruit (Cronje, 2009). Fruit bagging by placing of paper around and

on top of the fruit also reduced LD in ‗Tommy Atkins‘ and ‗Keitt‘ mango fruit (Cronje, 2009).

25

Modified atmosphere

Modified atmospheres have been used to reduce the browning of fresh-cut fruit, including for

mangoes. They are also used to reduce CI and disease on fresh mango fruit. The practice reduces

browning mainly by modifying tissue concentrations of O2, CO2 and/or C2H4 (Kader, 1989).

Bagging and coating could create a modified atmosphere for fruit (Kader, 1989).

Modified atmosphere packaging (MAP) combined with chemicals and low temperature (Zagory and

Kader, 1988, Rojas-Graü et al., 2009) is used to reduce browning and decay of fresh-cut fruit. MAP

created by thermo conglutination with Cryovac LDX-5406 film wrapping polystyrene plastic trays,

combined with 0.001 M 4-hexylresorcinol plus 0.05 M potassium sorbate and / or 0.5M D-

isoascrobic acid reduced browning of fresh-cut mangoes (González-Aguilar et al., 2000b). Coating

with 0.5 – 2% chitosan with an over-wrap of PVDC film (Wu-Yu Chemistry Co, Japan) and

holding at 6oC also reduced fresh-cut mango browning and decay (Chien et al., 2007).

Modified atmosphere packaging can help control CI of fresh fruit (Table 2.2). Modified atmosphere

packaging with reduced O2 (19.7%) and elevated CO2 (2.6%) concentrations reduced CI on ‗Nam

Dok Mai‘ mango fruit stored at 4oC with no change in flavour and decay. This treatment decreased

PPO activity and increased total phenolics to protect the fruit (Chidtragool and Ketsa, 2010).

Modified atmosphere packaging is also used to reduce disease in fresh fruit (Jitareerat et al., 2007,

Abd-AllA and Haggag, 2010). Coating ‗Tainong‘ mango fruit with 2% chitosan containing 1% tea-

polyphenols can reduce anthracnose (Wang et al., 2007b). Coating ‗Tommy Atkins‘ mango fruit

with carnauba wax was reported to reduce anthracnose and stem end rot with no flavour change

(Baldwin et al., 1999). Bentonite and bentonite combined with potassium sorbate coatings reduced

anthracnose on ‗Ivory‘ mango fruit (Liu et al., 2014). Using 12% (v / v) polyethylene emulsion wax

dipping after hot water brushing for 15 – 20 s reduced stem end rot on ‗Keitt‘ mango fruit (Prusky

et al., 1999).

Temperature control

Low temperature conditioning is a specific approach to avoid CI on ‗Alphoso‘ mango fruit (Thomas

and Joshi, 1988) (Table 2.2). Low temperature conditioning has also been reported for loquat (Cai

et al., 2006) and avocado (Woolf et al., 2003) fruits. As an alternative, cold shock treatment at 0°C

for 4 h and then transfer to 20°C for 20 h prior to storage at 2°C for 12 days reduced CI (Zhao et al.,

26

2006). The increases in glutathione and phenolics contents and of antioxidant enzymes (viz.

catalase and ascorbate peroxidase) were involved in induced chilling tolerance.

Heat treatment at 38°C for 24 or 48 h prior to cold temperature storage could also reduce CI

(McCollum et al., 1993, Nair et al., 2000) (Table 2.3). Hot water dipping at 53°C for 4 min or 45°C

for 4 min alleviated CI of pepper fruit and pomegranate fruit by increasing polyamine levels

(González-Aguilar et al., 2000a, Mirdehghan et al., 2007). Somewhat similarly, hot air conditioning

at 39 ± 1°C for 8 h prior to HWT at 45°C for 30 min or 47°C for 15 min alleviated heat damage of

‗Kensington‘ cultivar mango fruit (Jacobi et al., 1996, Jacobi et al., 2000) (Table 2.3).

Other factors

Nitric oxide fumigation at 10, 20 or 40 μL / L for 2 h alleviated decay of ‗Kensington Pride‘ mango

fruit stored at 5ºC and 94% RH (Zaharah and Singh, 2011). Exposure of ‗Tommy Atkins‘ mango

fruit to lower RH of ~ 90% inside X tend® film packaging reduced sapburn as compared to

maintaining fruit inside PE packaging with a higher RH of ~ 99% (Pesis et al., 2000). UV-C

treatment at 4.93 kJm-2

alleviated pathogen decay on ‗Haden‘ cultivar mango fruit (González-

Aguilar et al., 2007). UV-C has been reported to reduce CI for banana (Pongprasert et al., 2011) and

peach (Gonzalez‐Aguilar et al., 2004) fruits.

2.2.2.2 Chemicals

Use of various chemical treaments can reduce flesh browning of on fresh-cut mango fruit, CI,

sapburn, disease (anthracnose, stem end rot and black spot), and other flesh browning caused by

fruit flies (Table 2.5).

Treating with 0.5 – 1% (w / v) ascorbic acid (Lee et al., 2003), 0.5 – 1% (w / v) citric acid (Lee et

al., 2003), 0.1 – 0.5% (w / v) cysteine (Perez-Gago et al., 2006), 0.005% – 0.02% (w / v) of 4 –

hexylresorcinol (Perez-Gago et al., 2006), 0.75 – 2% (w / v) glutathione (Rojas-Graü et al., 2007),

and 0.75 – 2% (w / v) N-acetylcysteine (Rojas-Graü et al., 2007) reduced browning of fresh-cut

fruit. Ascorbic acid, an antioxidant, is commonly used to prevent enzyme-catalysed discolouration

of fruits by reducing the colourless diphenols. Citric, malic, or phosphoric acid can inhibit PPO

activity by reducing pH and / or chelating copper in a food product (Guerrero-Beltrán et al., 2005).

Cysteine reduces PPO activity by forming the colourless Cys-quinone-adducts (Dudley and

Hotchkiss, 1989). 4-Hexylresorcinol interacts with PPO to render an inactive complex incapable of

27

catalysing the browning reaction (Guerrero-Beltrán et al., 2005). Combined application of several

browning inhibitors can be more effective than those applied individually to reduce fresh-cut mango

browning (González-Aguilar et al., 2000b). For instance, a solution containing 4-hexylresorcinol (1

mM), potassium sorbate (50 mM) and D-isoascorbic acid under MAP atmosphere conditions was

tested to reduce browning of ‗Kent‘ mango fruit. The combination of anti-browning agents had a

greater association with reduced browning than MAP (González-Aguilar et al., 2000b). 1-

Methylcyclopropene at 1 μL / L for 6 h at 10oC was found to reduce browning of fresh-cut ‗Kent‘

and ‗Keitt‘ mango slices. Citric acid dipping at 5 g / L and cassava starch coating at 10 g / L

reduced browning of fresh-cut ‗Tommy Atkins‘ mango fruit. Ascorbic and citric acid in an alginate

coating reduced browning of fresh-cut ‗Kent‘ mango fruit (Robles-Sánchez et al., 2013). An

ascorbic acid solution of 250 – 1000 mg / kg (w:w = ascoribc acid: phosphoric acid solution

adjusted mango puree [pH = 3.5]) and a cysteine solution of 300 mg / kg (w : w = cysteine :

phosphoric acid solution adjusted mango puree [pH = 4.0]) lessened browning of mango puree

(Guerrero-Beltrán et al., 2005). These chemicals combined with 4-hexylresorcinol slowed down the

tissue darkening effects (Guerrero-Beltrán et al., 2005).

Exposure to methyl jasmonate (10 mM) vapour for 24 h at 25°C before storage at 7°C for 21 days

plus 5 days at 20°C reduced CI on ‗Tommy Atkins‘ mango (Gonzalez-Aguilar et al., 2000) and

‗Kent‘ mango (González-Aguilar et al., 2001) fruit. A similar effect for methyl jasmonate treatment

in reducing CI on guava fruit was found to be associated with higher antioxidant enzyme activity

(González-Aguilar et al., 2004, Cao et al., 2009). Also, 2,4-dichlorophenoxyacetic acid treatment at

150 mg / L by vacuum infiltration under low pressure (-50 kPa) at 25°C for 5 min reduced CI on

‗Tainong‘ mango fruit by enhancing endogenous abscisc acid (ABA) and gibberellin (GA30) levels

(Wang et al., 2008). Dipping ‗Zill‘ cultivar into either 5 mM oxalic acid or 2 mM salicylic acid for

10 min reduced CI probably by increasing the reducing status of ascorbate and glutathione,

decreasing the accumulation of O2- and increasing the accumulation of H2O2 (Ding et al., 2007).

De-stemming fruit in a 1% Cold Power ® detergent solution reduced sapburn on ‗Kensington‘ fruit

(O'Hare and Prasad, 1991), ‗Sindhri‘ and ‗Samar Bahisht Chaunsa‘ mango fruit (O'Hare and Prasad,

1991, O'Hare, 1994, Maqbool and Malik, 2008), but not as effeciently as 1% calcium hydroxide.

Treatment with 1% sodium hydroxide reduced sapburn on ‗Chausa‘ mango fruit more effectively

than 1% calcium hydroxide (Barman et al., 2015).

Calcium ascorbate is one of the common antibrowning agents that is currently used by the fresh-cut

apple industry (Karaibrahimoglu et al., 2004, Fan et al., 2005). It could reduce disease by

28

maintaining the cell wall structure with a synthesis of calcium pectate (Alandes et al., 2009).

Calcium supply can also increase cell turgor pressure and stabilize cell membranes by binding to

phospholipids to prevent degradation of phospholipids (Chéour Foued et al., 1992). Postharvest

treatment with calcium ascorbate at a high concentration of 20% (w / w) prevented browning more

effectively on fresh-cut ‗Braeburn‘ apple slices than did lower concentrations ranging through 0, 2,

6 and 12% (Aguayo et al., 2010). Treatment with 7% calcium ascorbate reduced browning on ‗Gala‘

apple slices, even including irradiated samples, when compared with no calcium ascorbate (Fan et

al., 2005). Similarly, 5% calcium ascorbate combined with acidic electrolyzed water or with

peroxyacetic acid treatments inhibited browning on fresh-cut apples (Wang et al., 2007a). Vacuum

infiltration of salicylic acid (1 mM) for 2 min at a low pressure (-80 kPa) with an additional 10 min

at atmospheric pressure reduced anthracnose was associated with higher PAL and β-1,3-glucanase

activity as well as H2O2 and O2- (Zeng et al., 2006). Treatments with 20 or 40 mM postassium

oxalate or ammonium oxalate solution for 10 min reduced the disease severity of ‗Zill‘ mango fruit

by increasing PPO and POD activities and by elevating total phenolics concentration (Zheng et al.,

2007, Zheng et al., 2012). Insecticides and fungicides at low concentrations are generally used to

kill fruit insects and pathogens, and ultimately reduce browning. Associated with these agents,

prochloraz is a common fungicide that can be used for postharvest treatments of mango fruit. A

single spray treatment with 900 μg ml−1

prochloraz was used commercially until 1998. Recently,

prochloraz treatment has been combined with hot water brushing to reduce stem end rot and black

spot diseases of mango fruit (Prusky et al., 1999). Insecticides that include organophosphates,

carbamates and pyrethroids have been used on mango fruit to control insects (Ahmad et al., 2010).

2.2.2.3 Biological

The use of biological control with microorganisms is another approach to control postharvest

disease on mango fruit. It can be based on the use and management of beneficial microflora that

already exist on fruit and vegetable surfaces or on the artificial introduction of antagonists against

postharvest disease-causing organisms (Wisniewski and Wilson, 1992). Revundimonas diminuta

isolate B-62-13, Stenotrophomonas maltophilia L-16-12, a member of Enterobacteriaceae L-19-13,

Candida membranifaciens F-58-22 microbes have been shown to reduce the severity of anthracnose

on ‗Amaba Kurfa‘ mango fruit (Kefialew and Ayalew, 2008). Bacillus licheniformis, a biological

control agent at 107

cfu / mL combined with hot water treatment of 5 min at 45ºC followed by ¼

strength recommended rate prochloraz treatment for 20 s and waxing with CitrashineTM

(Citrashine

29

Pvt Ltd., Johannesburgh, South Africa) is another method controlling anthracnose and stem end rot

(Govender et al., 2005).

Overall, physical, chemicals and biological factors for reducing browning disorders in mango fruit

were summarized in Table 2.2, Table 2.3, Table 2.4and Table 2.5.

30

Table 2.2 Physical factors that may reduce browning disorders (mechanical damage and CI) of mango fruit (M. indica L.)

Treatment and conditions Cultivar Browning

disorders

lessened

Source

Packaging (foam netting) ‗Nam Dok Mai‘ Mechanical

damage

Chonhenchob and

Singh (2003)

Microperforated polyethylene or X tend® film packaging (5% CO2 and 10% O2) ‗Tommy Atkins‘

and ‗Keitt‘

CI Pesis et al. (2000);

Microperforated X tend® film packaging (19.7% O2 and 2.6% CO2) ‗Nam Dok Mai‘ CI Chidtragool and Ketsa

(2010)

No fumigation (10 or 20 or 40 μL / L for 2 h) ‗Kensington

Pride‘

Decay (disease) Zaharah and Singh

(2011)

Carbon dioxide atmosphere (5 – 10%) ‗Kensington

Pride‘

CI O'Hare and Prasad

(1992)

Heat treatment (38°C for 24h or 48 h) ‗Kensington

Pride‘

CI McCollum et al.

(1993), Nair et al.

(2000);

Cold shock treatment (0°C for 4 h before fruit storage at 2°C) ‗Wacheng‘ CI Zhao et al. (2006)

Low temperature conditioning (Fruit held and ripened at 20°C and 80 – 90% RH,

and subsequently kept at 5 or 10°C up to 14 days; fruit held at 10°C for a minimum

period of 30 days and then held at 27 – 34°C until fruit ripened)

‗Alphoso‘ CI Thomas and Joshi

(1988)

31

Table 2.3 Physical factors that may reduce browning disorders (heat damage and disease) of mango fruit (M. indica L.)

Treatments and conditions Cultivar Browning disorders lessened Author(s)

Conditioning hot air (38°C from 0 to 24 h prior to

HWT at 46°C with fruit core about 45°C for 30 min)

‗Kensington Pride‘ Heat damage (skin scald) and / or

Disease

Jacobi et al. (1996),

Jacobi et al. (2000)

Coating with cellulose-based polysaccharide or

carnauba wax

‗Tommy Atkins‘ Anthracnose or stem end rot; Baldwin et al. (1999)

Coating with 0.2 – 2% chitosan;

Coating with 2% chitosan containing 1% tea

polyphenols

‗Sanara‘

‗Tainong‘

Anthracnose Abd-AllA and Haggag

(2010).

Wang et al. (2007b)

Coating with bentonite (B: DW = 15:1) / potassium

sorbate (B: DW: potassium sorbate = 15: 1: 0.7)

‗Ivory‘ Stem end rot Liu et al. (2014)

HWT (53°C for 10 min) ‗Carabao‘ Anthracnose, stem end rot and

fruit fly damage

Buganic Jr et al. (1996)

A combination of hot water brushing (48 – 64°C) and

dipping fruit in 12% polyethylene emulsion wax

‗Tommy Atkins‘, ‗Keitt‘,

‗Haden‘, ‗Kent‘, ‗Palmer‘ and

‗Lily‘

Alternaria black spot Prusky et al. (1996),

Prusky et al. (1999)

UV-C (4.93 kJm-2) ‗Haden‘ Fungi decay González-Aguilar et al.

(2007)

Polyethylene-based wax ‗Kensington Pride‘ Sapburn Shorter and Joyce

(1994)

32

Table 2.4 Physical factors that may reduce browning disorder (sapburn) of mango fruit (M. indica L.)

Physical Treatments Cultivar Browning disorders lessened Source

Sap harvested time (morning than

afternoon)

‗Samar Bahisht Chaunsa‘ Sapburn Maqbool (2007), Amin et al.

(2008)

De-sap handling Sapburn Holmes et al. (1992)

Low humidity in X tend® film

packaging (RH = 90%)

‗Tommy Atkins‘ and ‗Keitt‘ Sapburn Pesis et al. (2000)

33

Table 2.5 Chemicals that may reduce browning disorder of mango fruit (M. indica L.)

Chemicals and conditions Cultivar Browning disorders

lessened

Source

2,4- Bichlorophenoxyacetic acid (150 mg / L vacuum-

infiltrated)

‗Tainong‘ CI or anthracnose Wang et al. (2008);

Hot water (T: 55°C) including 225 and 900 μg / ml

prochloraz brushing for 15 – 20 s and 12% soluble

solids, polyethylene emulsion wax containing 75 – 175

μg / ml 2, 4 – dichlorophenoxyacetic acid

‗Tommy Atkins‘ and ‗Keitt‘ Stem end rots Kobiler et al. (2001)

Oxalic acid (5 mM) ‗Zill‘ CI Zheng et al. (2007), Zheng et

al. (2012)

Salicylic acid (2 mM) ‗Zill‘ CI Zheng et al. (2007)

Calcium hydroxide (1% [w / v]) ‗Kensington Pride‘ Sapburn O'Hare and Prasad (1991),

Maqbool and Malik (2008)

Sodium hydroxide (1% for 5 min) followed by 0.5%

alum

‗Samar Bahisht Chaunsa‘ Sapburn Barman et al. (2015)

Salicyclic acid or potassium phosphonate (1000 mg/L)

followed by hot water treatment including 3% aqueous

sodium bicarbonate (51.5°C for 3 min)

anthracnose Dessalegn et al. (2013)

2,4-Dichlorophenoxyacetic acid Stem end rot Kobiler et al. (2001)

34

Table 2.5 (continued)

Chemicals and conditions Cultivar Browning disorders

lessened

Source

Ammonium oxalate (30 mM) and potassium oxalate (30

mM)

‗Xiaojinhuang‘ Anthracnose; Zheng et al. (2012)

HCl (50 mM) and / or prochloraz (45 μg ml-1

) followed

by hot water spray and brushing (HWB) for 15 – 20 s

Stem end rot Prusky et al. (2006)

Ethanol (300 ml / L) combined with hot water treatment

(50°C for 60 s)

‗Tommy Atkins‘ Disease Gutiérrez-Martínez et al.

(2012)

35

2.3 The Mechanism of Lenticel Discolouration and Under-skin Browning

Lenticels are macroscopic pores that regulate gas exchange in plant tissue (Kader and Saltveit,

2003), including mango fruit (Figure 2.5). Lenticel discolouration (LD) is a cultivar dependant

discolouration that afflicts ‗Keitt‘, ‗Kent‘ and ‗Tommy Atkins‘ mango fruit (Du Plooy et al., 2006).

This disorder also affects ‗B74‘ (CalypsoTM

) mango cultivar more than other Australia mango

cultivars, such as ‗Honey Gold‘ and ‗Kensington Pride‘ (Joyce et al., 2011). The entry of air and

water into lenticels was firstly reported to be a casual factor in causing LD (Tamjinda et al., 1992).

Wind or cold might increase LD on mango fruit (Pesis et al., 2000). Over the years, the following

factors including moisture status at harvest, cultivar differences, postharvest handling and storage

temperature might increase LD on fruit (Table 2.6). However, the following factors including

drying of orchard soil, paper bagging around and on top of fruit, use of insect predator, harvesting

methods, and de-sapping and storage conditions possibly decreased LD (Table 2.6).

36

Table 2.6 Preharvest, postharvest and other factors increasing LD of fruit

Factors Cultivar(s) Source

Preharvest

factors

Occurrence of rain at harvest;

Fruit are harvested wet;

Wind and cold.

Avocado;

Avocado;

Mango (Unknown cultivar).

Duvenhage, 1993;

Duvenhage, 1993.

Pesis et al., 2000.

Postharvest

factors:

Imbibing fruit in water for 2 h

Dipping fruit in hot water at 45°C for 30 min;

Dipping fruit in hot water at 46°C for 120 min;

A combination of hot water and hot air;

Washing fruit in one or several disinfectants or soap

including Agral®, Cold Power

® or Mango Wash

®;

Washing fruit in ambient water;

Washing fruit in calcium hydroxide solution;

Storage temperature below 10 – 12°C;

Irradiation;

Storage fruit high temperature (fruit) and low humidity

in baulk bin.

Avocado;

Mango (‗Kensington Pride‘);

Mango (‗Tommy Atkins‘)

Mango (‗Kensington Pride‘)；

Mango (Unknown cultivar);

Mango (Unknown cultivar);

Mango (‗Tommy Atkins‘)

Mango (‗Tommy Atkins‘ and ‗Keitt‘)

Mango (‗B74‘)

Mango ( ‗Kensington Pride‘ )


Everett et al., 2008;

Jacobi et al., 2001;

Mitcham and Yahia, 2009;

Jacobi et al., 1996;

Bally, et al., 1997;

O‘Hare et al., 1996;

Simão de Assis et al., 2009;

Pesis et al., 2000;

Joyce et al., 2011;

Johnson et al., 1990b

Cronje, 2009.

Others: Cultivars;

Sap

(B74 > other cultivars including

‗Kensington Pride‘, ‗R2E2‘ and ‗Honey

Gold‘;


Joyce et al., 2011;

Pesis et al., 2000.

37

Table 2.7 Preharvest, postharvest and other factors decreasing LD of fruit

Factors Cultivar(s) Source

Preharvest

factors

Drying of orchard soil to a level of at least – 50 kPa Mango (unknown cultivar) Johnson et al.,

1997;

Postharvest

factors:

Different picking method to avoid sap and decreased storage time in the

packhouse and adopted procedures in the pckline;

Fruit bagging around and on top of fruit;

The weaver ants, Oecophyll smaragdina (Fab.) plus soft chemicals

(potassium) treatment;

Storage of fruit in bulk bins without paper lining or ventilation;

Storaging of fruit at low temperature (fruit and air) and high humidity in bulk

bins

Mango (‗Tommy Atkins‘

and ‗Keitt‘);


and ‗Keitt‘);

Mango (unknown

cultivar);


and ‗Keitt‘)

Cronje, 2009;

Cronje, 2009;

Peng and

Christian, 2005;

Cronje, 2009.

38

At the cellular level, LD may be the result of endomembrane collapse, possibly induced by the

release of toxic compounds from cork cambium and cork cells (Bezuidenhout, 2005) and / or the

liberation of phenolics in response to physiological stress of the tissue surrounding lenticels

(Beckman, 2000, Bezuidenhout, 2005). Mango sap can destroy the integrity of membranes and

allow PPO to come into contact with phenolics (Joel, 1981, Loveys et al., 1992, Robinson et al.,

1993). In turn, brown or dark LD occurs upon accumulation of melanin in the cell walls

(Bezuidenhout, 2005). Red lenticel discolouration may occur with the accumulation of

anthocyanins (Kangatharalingam et al., 2002), flavonoids (Dixon and Paiva, 1995) and

phenylpropanoid derivatives (Du Plooy et al., 2009). Another view is that, LD involves an active,

stress-related self-defence mechanism without necessarily entailing structural disorganisation, such

as vacuolar collapse or membrane disintegration. However, based on transmission electron

microscopy observations, it would still entail conjugation of simple phenolics (Du Plooy et al.,

2009). Nonetheless, the full detailed mechanism of LD in physico-chemical terms is relatively

poorly understood (Joyce et al., 2011).

Figure 2.5 Transverse section of lenticel of ‗Tommy Atkins‘ mango fruit (Bezuidenhout et al., 2005)

Under-skin browning (USB) occurs in ‗Honey Gold‘ mango fruit after transportation (Hofman et al.,

2009b). While a few reports have been published, the cause and mechanism of USB are unclear.

With USB, affected tissue features retention and / or accumulation of starch (Marques et al., 2012).

‗Honey Gold‘ fruit harvested in the afternoon was reportedly more susceptible for USB as

compared to fruit harvested in the morning in commercial market (P. Hofman, pers. comm., 2012).

39

Abrasion of the fruit skin has been used a test for inducing USB on fruit (Hofman et al., 2009).

Road transportation combined with 12 – 14°C increased the incidence of USB by 83% as compared

to no road transportation combined with 12 – 14°C (Marques et al., 2012). Delays of one day at 27

– 35ºC before packing plus two days at 18 – 20°C after packing before moving fruit to 12 – 14°C

and road transportation, reduced the incidence of USB by 83% as compared to moving fruit to 12 –

14°C within 13 h after picking and road transportation (Marques et al., 2012).

2.4 Perspective and Conclusions

Browning disorders on mango fruit induced by physical, chemical and biological agents involve

enzymes (viz., PPO and POD) and substrates (viz., oxygen and total phenolics). In the context of

the present thesis, LD on ‗B74‘ mango fruit becomes worse after ɣ- irradiation and USB occurs

after transportation. Postharvest treatments (e.g., modified atmosphere packaging, anti-browning

agents and degree of fruit ripeness) prior to ɣ- irradiation might potentially be used to reduce LD.

Better understanding of the mechanism of browning underpinning LD induced by ɣ- irradiation

could help toward devising measures to reduce LD on ‗B74‘ mango fruit. USB in ‗Honey Gold‘

mango fruit may be induced by sap leakage from resin ducts beneath the skin surface upon physical

damage during transportation. As with LD, understanding the biochemistry of USB might help

towards managing this similarly unsightly browning disorder.

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56

Postharvest Treatments Effects on Reducing LD after γ-Chapter 3

Irradiation

Abstract

Lenticel discolouration (LD) is a common skin disorder on ‗B74‘ mango fruit especially after γ-

irradiation. Postharvest chemical treatments, including ascorbic acid, citric acid, calcium ascorbate

and calcium chloride, postharvest waxing treatments including different concentration and multiple

coatings of carnauba wax dipping, postharvest bagging including polyethylene bagging for one and

two days with and without nitrogen flushing, bagging for eight days using different types of bags

with and without nitrogen flushing or high relative humidity (RH) and bagging at varying degrees

of fruit ripeness with and without nitrogen flushing, and varying degrees of fruit ripeness prior to γ-

irradiation were investigated towards potentially reducing LD induced by γ-irradiation. Fruit quality

parameters including LD, skin colour, firmness, skin browning, weight loss, titratable acidity and

soluble solids concentration were measured. γ-Irradiation significantly (P < 0.05) increased LD.

Chemicals treatments did not reduce LD after γ-irradiation. However, they adversely increased skin

browning except the 100 mM citric acid treatment. Three layers of 75% carnauba wax treatment

significantly (P < 0.05) decreased LD after γ-irradiation. Macro-perforated bags and paper bags

treatments did not reduce LD. High RH in macro-perforated bags and nitrogen in polyethylene bags

did not reduce LD either. Polyethylene bagging treatments applied prior to irradiation significantly

(P < 0.05) decreased LD while fruit remained in the bags. However, LD increased soon after fruit

were removed from the bags. Three layers of 75% carnauba wax and polyethylene bagging for eight

days treatments delayed skin colour change, fruit softening and weight loss and caused failure of

fruit to ripen. Irradiating partly ripe (sprung) fruit increased LD significantly (P < 0.05) less for the

first 5 days than irradiating hard fruit. When fruit at different stages of ripeness all reached eating

ripe, the initial treated sprung fruit had significantly (P < 0.05) lower LD than for other stages of

fruit ripeness, with no adverse effects on skin colour, firmness, titratable acidity and soluble solids

concentration. Therefore, irradiating fruit at the sprung stage rather than irradiating fruit at the hard

stage is the most promising approach identified to reduce LD associated with irradiation.

Keywords: ɣ-irradiation, lenticel discolouration, mango fruit, postharvest treatments, quality

parameter

57

3.1 Introduction

The ‗B74‘ mango cultivar was bred from a cross of ‗Kensington Pride‘ and ‗Sensation‘ cultivars in

Australia and has now been commercialised as Calypso™ since 2000 (Chapter 1). This cultivar is

grown in the Northern Territory, Queensland and Western Australia and constitutes ~ 20% of total

Australia mango production each year (AMIA, 2014). It is typically harvested from September to

March in Australia (AMIA, 2014).

Lenticels are macroscopic pores in plant tissues that regulate gas exchange (Kader and Saltveit,

2003). Lenticel discolouration (LD) is a physiological skin disorder of mango fruit that is evident as

red, brown or black ‗halos‘ surrounding lenticels. LD is a common disorder on mango fruit all over

the world (Du Plooy et al., 2009). ‗B74‘ is relatively more susceptible to LD than other cultivars

such as ‗Honey Gold‘, ‗Kensington Pride‘ and ‗R2E2‘ (Joyce et al., 2011). Exposure to γ-irradiation

with a commercial dose of 400 – 500 Gy, a phytosanitary treatment, has been reported to markedly

increase LD (Hofman et al., 2009).

A range of chemicals, applied postharvest, have been used to reduce browning in vegetables and

fruits, especially on fresh-cut fruit. For example, treatments with ascorbic acid and citric acid have

been shown to reduce browning of peaches (Li-Qin et al., 2009), Chinese water chestnuts (Jiang et

al., 2004) and lettuces (Altunkaya and Gökmen, 2008). These chemicals decreases tissue browning

either by reducing o-quinones back to phenolic compounds before they form brown melanin

pigments (Pizzocaro et al., 1993, Gil et al., 1998) or by reducing pH and / or chelating copper

(McEvily, 1992). Applications of compounds containing Ca2+

, such as calcium chloride and

calcium ascorbate, have been reported to reduce browning in fresh-cut apple by maintaining cell

membrane and structure (Luna-Guzmán and Barrett, 2000, Fan et al., 2005, Aguayo et al., 2010).

Edible coatings and bagging treatments have been shown to reduce browning on fruit and

vegetables via the creation of modified atmospheres around the harvested product and protection

against physical injury (Soliva‐Fortuny et al., 2002, Morehouse and Komolprasert, 2004, Pérez-

Gago et al., 2010, Kore and Chakraborty, 2014). Treatment with carnauba wax, a natural edible

coating (Baldwin et al., 1999, Chien et al., 2007, Dang et al., 2008) reduced pomegranate fruit

tissue browning (Barman et al., 2011) and pear friction browning (Amarante et al., 2001). Short-

term exposure to nitrogen-rich atmospheres can also extend the green life of fruit (Klieber et al.,

2002) by reducing available oxygen for tissue browning reaction (Thompson, 2010).

58

The ripeness stage has been reported to influence the response of mango fruit to postharvest

treatments. For example, immature ‗Kensington‘ mango fruit were damaged more by hot air insect

disinfestation treatments than mature fruit (Jacobi et al., 1995). It has been reported that the levels

of metabolites involved in tissue browning reactions (viz., polyphenol oxidase, peroxidase and total

phenolics) can vary substantially in ‗Ataulfo‘ mango fruit skin during postharvest storage (Palafox-

Carlos et al., 2012). However, the sensitivity of mango fruit at different ripeness stages to

developing LD induced by γ-irradiation has not yet been thoroughly investigated.

LD on mango fruit is hypothesised to be an enzymatic browning process which is associated with

enzymes, phenolics and oxygen. In the present study, the effect of chemicals (anti-browning agents)

and fruit ripeness stage treatments on limiting enzymatic browning of ‗B74‘ mango fruit lenticels

were tested. Waxing and bagging fruit were also examined as a means to reduce enzymatic

browning by lowering the concentration of oxygen surrounding fruit and / or by decreasing

endogenous oxidative enzymes activity and phenolic compounds. The effects of these treatments on

fruit quality parameters including LD, skin colour, firmness, weight loss, titratable acidity and

soluble solids concentration were evaluated.

3.2 Materials and Methods

3.2.1 Materials

Hard green mature ‗B74‘ fruit (Mangifera indica L) (dry matter content Table A 1.1) were grown

under standard commercial conditions at an orchard near Childers (25°17‘S, 152°17‘E) in Southeast

Queensland, Australia or an orchard near Katherine (14°46‘S, 132°26‘E) in the Northern Territory,

Australia. Harvested fruit were de-stemmed and de-sapped in a solution of Mango Wash®

(Septone,

ITW AAMTech, NSW, Australia). They were taken to a nearby packinghouse and treated and

packed under standard commercial conditions, including fungicide treatment (Sportak®, a.i.

prochloraz, Bayer Crop Science, VIC, Australia), brushing, drying and sorting (Hofman et al.,

2010). The fruit were graded for uniform quality and size. They were then packed into single layer

fibreboard trays with polyethylene liners. The fruit were transported to the Ecosciences Precinct

(27°49‘S, 153°03‘E) in Brisbane, Queensland, Australia or the Maroochy Research Facility in

Nambour (26°62‘S, 152°95‘E), Queensland, Australia by car and / or air-plane. They were assigned

to treatments in a completely randomised design.

59

3.2.2 Experiment 1. Effects of chemicals

3.2.2.1 Citric acid and ascorbic acid in the 2011 – 12 season

Fruit from Southeast Queensland collected in the 2011 – 12 season were dipped into 100 and 500

mM citric acid (BDH Australia Pty Ltd, VIC, Australia), and 100 and 500 mM ascorbic acid (BDH

Australia Pty Ltd, VIC, Australia) for 10 min (Figure 3.1). Fruit treated with distilled water were the

controls. The fruit were put on tissue paper to dry at room temperature (~ 30°C) for 1 h. Fruit were

then prepared for exposure to -irradiation or not as described in Section 3.2.6. Thereafter, the fruit

were maintained in a ripening room at 20°C and 90 – 100% relative humidity (RH) until fruit

reached eating ripe. Five individual fruit replicates per treatment were used in this experiment.

Individual fruit was taken as the replicate.

3.2.2.2 Ascorbic acid, calcium chloride and calcium ascorbate in the 2012 – 13 season

Fruit from Southeast Queensland collected in the 2012 – 13 season were treated with 100, 50 and 10

mM calcium ascorbate (Melrose Laboratories Pty Ltd, VIC, Australia), 100 mM ascorbic acid

(BDH Australia Pty Ltd, VIC, Australia) and 100 mM calcium chloride (BDH Australia Pty Ltd,

VIC, Australia) as above. Fruit treated with distilled water were the controls. Fruit were then

prepared for exposure to -irradiation or not as described in Section 3.2.6 and then maintained in a

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Fifteen individual fruit

replicates per treatment were used in this experiment. Individual fruit was taken as the replicate.

60

3.2.3 Experiment 2. Effects of waxing

3.2.3.1 Carnauba wax concentration in the 2011 – 12 season

Fruit from Southeast Queensland collected in the 2011 – 12 season were dipped once into 10, 20, 40

and 80% (v / v) carnauba wax (Natural Shine™ TFC 210, Pace International LLC, WA, USA) for

10 s. The fruit were then air-dried at room temperature (~ 26°C) for 1 h (Figure 3.2). Fruit dipped in

distilled water were the controls. Fruit were then prepared for exposure to -irradiation or not as

described in Section 3.2.6 and then maintained in a ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe. Ten individual fruit replicates per treatment were used in this experiment.


3.2.3.2 Multiple coatings of carnauba wax in the 2012 – 13 season

Fruit from Southeast Queensland collected in the 2012 – 13 season were dipped once and three

times in 75% (v / v) carnauba wax (Natural Shine™ TFC 210, Pace international LLC, WA, USA)

for 10 s, and air-dried at room temperature (~ 26°C) for 1 h as above. Fruit were air-dried for 30

min between the second and third coatings of carnauba wax. Fruit dipped in distilled water were the

controls. Fruit were then prepared for exposure to -irradiation or not (Section 3.2.6) and then

maintained in a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Fifteen

individual fruit replicates per treatment were used in this experiment. Individual fruit was taken as

the replicate.

Figure 3.1 Image of ‗B74‘ mango fruit during chemical dip treatments

61

3.2.4 Experiment 3. Effects of bagging

3.2.4.1 Polyethylene bagging in the 2011 – 12 season

Individual fruit from Southeast Queensland collected in the 2011 – 12 season were enclosed in 20 x

19 cm polyethylene GLAD®

snap lock bags (Clorox Australia Pty Limited, NSW, Australia) with

and without nitrogen gas flushing. High purity nitrogen (BOC, Kunda Park, QLD, Australia) was

introduced into bags via a plastic tube connected to a pressurised cylinder of gas. The tube was

inserted into a small opening in the bottom edge of each bag that had been partly sealed with a heat

sealer. The bag atmosphere was flushed with nitrogen for 1 min. Before starting nitrogen flushing,

the air inside the partly sealed bag was pushed out. Fruit not held in bags were the controls. Fruit

remained inside bags for γ-irradiation or not (Section 3.2.6). The fruit were removed from bags at

24 and 48 h after γ-irradiation, and then maintained in a ripening room at 20°C and 90 – 100% RH

until fruit reached eating ripe. Fifteen individual fruit replicates were used in this experiment.


3.2.4.2 Bagging with different types of bags in the 2012 – 13 season

Individual fruit from Southeast Queensland collected in the 2012 – 13 season were enclosed in 22 ×

22 cm polyethylene bags (permeability characteristics: 24,000 mL. bag-1

. day-1

. atm-1

O2 and 19,000

mL. bag-1

. day-1

. atm-1

CO2, Amcor LifeSpan, NSW, Australia) with and without nitrogen flushing

Figure 3.2 Image of ‗B74‘ mango fruit during air-drying following dip treatment with carnauba wax

62

(as described in Section 3.2.4.1), 22 × 22 cm macro-perforated bags (Amcor LifeSpan, NSW,

Australia) with and without high RH (described below), and 19 × 30 Kraft paper (80 g.m-2

) bags,

respectively (Figure 3.3). High levels of RH in the macro-perforated bags were created by placing a

free water source in bags. Briefly, a soil wetting hydrogel crystals (Woolworths Supermarkets,

Australia) was placed inside 4 × 5 cm bags made from baby diapers. The diaper bags were then

heat-sealed closed and immersed into distilled water to trigger absorption of water by the hydrogel.

The diaper bags were placed into the respective macro-perforated bags. Fruit that were not bagged

were the controls. Fruit remained inside bags for γ-irradiation or not as described in Section 3.2.6.

The fruit were removed from bags after irradiation plus storage in a ripening room at 20°C for eight

days. The fruit were then maintained in a ripening room at 20°C and 90 – 100% RH until fruit

reached eating ripe. Fifteen individual fruit replicates per treatment were used in this experiment.


3.2.4.3 Polyethylene bagging fruit of different ripeness stages in the 2013 – 14 season

Fruit from Southeast Queensland collected in the 2013 – 14 season were maintained in the ripening

room at 20°C and 90 – 100% RH for three and eight days until they reached the rubbery and sprung

stages of firmness, respectively. Individual fruit at each stage were then enclosed in polyethylene

bags (Amcor LifeSpan, NSW, Australia) with and without nitrogen flushing respectively as per

Section 3.2.4.1. Fruit not held in bags were the controls. Fruit remained inside bags for γ-irradiation

or not as described in Section 3.2.6. The fruit were removed from bags after irradiation plus storage

in a ripening room at 20°C and 90 – 100% RH for eight days. The fruit were then maintained in a

ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Ten individual fruit

replicates per treatment were used in this experiment. Individual fruit was taken as the replicate.

63

3.2.5 Experiment 4. Effects of fruit ripeness stage

3.2.5.1 Different ripeness stages of fruit grown in Southeast Queensland in the 2013 – 14 season

Fruit from the same batch used in Section 3.2.4.3 were maintained at 20°C and 90 – 100% RH for 0,

3 and 8 days until they reached ripeness stages of hard, rubbery and sprung firmness, respectively.

Fruit were then prepared for exposure to -irradiation or not as described in Section 3.2.6. Ten

individual fruit replicates per treatment were used in this experiment. Individual fruit was taken as

the replicate.

3.2.5.2 Different ripeness stages of fruit grown in the Northern Territory in the 2013 – 14 season

Fruit were maintained at 20°C and 90 – 100% RH for 0, 5 and 8 days until they reached hard,

rubbery and sprung firmness stages, respectively. Fruit were then prepared for -irradiation

exposure or not in Section 3.2.6. Ten individual fruit replicates per treatment were used in this

experiment. Individual fruit was taken as the replicate.

3.2.6 γ-Irradiation

Fruit were packed into fibreboard trays in a completely randomised fashion and transported by car

to Steritec, a commercial γ-irradiation facility near Narangba, Queensland, Australia within 1 h of

the pre-irradiation treatments. Half of the fruit for each postharvest treatment were exposed to a

Figure 3.3 Image of ‗B74‘ mango fruit exposed to different bags treatments

64

commercial dose of -irradiation (Table A 1.1) from a cobalt-60 source (Figure 3.4). The remaining

half of the fruit were not exposed to -irradiation. The fruit were then transported back to the

Ecosciences Precinct or the Maroochy Research Facility by car. In one sub-experiment with fruit

ripeness stage treatments, fruit from the Northern Territory were air-freighted to the Australian

Nuclear Science and Technology Organisation irradiation facility at Lucas Heights in Sydney,

Australia for γ-irradiation.

3.2.7 Quality assessment

All fruit were regularly assessed for quality parameters including LD, skin colour, firmness and skin

browning based on rating scales developed by Hofman et al. (2010) (Table 3.1).

Figure 3.4 Image of ‗B74‘ mango fruit inside fibreboard trays prior to γ-irradiation

65

Table 3.1 Rating scales for LD severity, skin colour (based on the proportion of the non-blushed area with yellow skin colour), firmness and skin

browning of ‗B74‘ mango fruit (Hofman et al., 2010)

Rating LD severity Skin colour Firmness Skin browning

0 No LD Hard (no ‗give‘ in the fruit) No

1 Light discolouration on ≤ 25% of the surface or dense, pronounced

discolouration on ≤ 5% of the surface, not cracked

0 – 10% Rubbery (slight ‗give‘ in the

fruit with strong thumb

pressure)

< 1 cm2

2 Light discolouration on ≤ 50% of the surface or dense, pronounced

discolouration on ≤ 10% of the surface, not cracked

10% – 30% Sprung (flesh deforms by 2 -

3mm with moderate thumb

pressure)

1 – 3 cm2 (3%)

3 Scattered pronounced discolouration on ≤ 50% of the surface, or dense,

pronounce discolouration on > 25% of the surface, not cracked

30% – 50% Firm soft (whole fruit deforms

with moderate hand pressure)

3 – 12 cm2

(10%)

4 Dense, pronounced discolouration on ≤ 50% of the surface 0 – 70% Soft (whole fruit deforms with

slight hand pressure)

12 cm2 (10%) –

5%

5 Dense, pronounced discolouration on > 50% of the surface 70% – 90% More than 25%

6 90% –

100%

66

3.2.8 Weight loss

Fruit weight loss was expressed as a relative proportion (%) by calculating the initial fresh weight

minus the final fresh weight and dividing by the initial fresh weight (Parra et al., 2014).

3.2.9 Titratable acidity (TA) and soluble solids concentration (SSC)

When fruit reached eating ripe, flesh samples were collected from five fruit with three replicates per

treatment. The replicate used for this parameter is different from the replicate used for quality

parameters. Briefly, the fruit skin was removed and flesh samples were excised from fruit cheeks.

The flesh samples were diced and stored at – 20°C for soluble solids concentration and titratable

acidity analysis within 2 months. Juice was extracted from the samples by squeezing the thawed

flesh through two layers of cheesecloth. The soluble solids concentration of juice samples was

measured using a digital pocket refractometer (PAL-1, Atago Co. Ltd, Tokyo, Japan) and expressed

as ° Brix. The TA of juice samples was determined for 10 g samples by titration with 0.1 M NaOH

(Melrose Laboratories Pty Ltd, VIC, Australia) to an end point pH of 8.1 and / or to end point

colour change with 0.4% (4 g dissolved in 100ml 95% ethanol) phenolphthalein indicator (Melrose

Laboratories Pty Ltd, VIC, Australia) (El Ghaouth et al., 1991). TA was calculated and expressed

as % citric acid equivalents.

3.2.10 Experiment design and statistical analyses

Completely randomised designs were used for all experiments. Repeated measurement ANOVA

was used in the statistical analyses of changes in LD, skin colour, firmness in four experiments and

skin browning in chemical treatments. The same repeated measurement ANOVA analyses was used

for weight loss in Sections 3.3.2.2, 3.3.3.1 and 3.3.4.2. However, a general ANOVA analyses was

used on weight loss in Sections 3.3.3.2 and 3.3.3.3 becaused of limited data achieved. The same

general ANOVA analyses was used on titratable acidity, soluble solids concentration for Sections

3.3.2.2, 3.3.4.1 and 3.3.4.2, and on skin colour and LD for Sections 3.3.4.1 and 3.3.4.2 on the day of

eating ripe.

The treatment factors in Section 3.3.1.1 for the parameters of LD, skin colour, firmness and skin

browning were irradiation (irradiation and non-irradiation) and chemicals (distilled water, 100 and

500 mM ascorbic acid and citric acid). The factors in Section 3.3.1.2 for the parameters of LD and

skin browning were irradiation (irradiation and non-irradiation) and chemicals (distilled water, 100

67

mM calcium chloride, calcium ascorbate and ascorbic acid, 10 and 50 mM calcium ascorbate). The

factors in Section 3.3.2.1 for the parameters of LD, skin colour, firmness and weight loss were

irradiation (irradiation and non-irradiation) and waxing (10, 20, 40, 80% and distilled water). The

factors in Section 3.3.2.2 for the parameters of LD, skin colour, firmness and weight loss were

irradiation (irradiation and non-irradiation) and waxing (One and three layers of 75% carnauba wax,

and distilled water). The factors in Section 3.3.3.1 for the parameters of LD, skin colour, firmness

and weight loss were irradiation (irradiation and non-irradiation) and bagging (bagging for 24 h

[one day] with and without nitrogen flushing, bagging for 48 h [two days] with and without

nitrogen flushing and no bag). The factors in Section 3.3.3.2 for the parameters of LD, skin colour

and firmness were irradiation (irradiation and non-irradiation) and bagging (polyethylene bagging

with and without nitrogen flushing for eight days, macro-perforated bagging with and without high

RH for eight days, paper bag for eight days and no bag). The factors in Section 3.3.3.3 for the

parameters of LD, skin colour and firmness were fruit ripeness stage (hard, sprung and rubbery),

irradiation (irradiation and non-irradiation) and bagging (no bag, and polyethylene bag with and

without nitrogen flushing). The factors in Section 3.3.4.1 for the parameters of LD, skin colour and

firmness were fruit ripeness stage (hard, sprung and rubbery) and irradiation (irradiation and non-

irradiation). The factors in Section 3.3.4.2 on LD, skin colour, firmness and weight loss were fruit

ripeness stage (hard, sprung and rubbery) and irradiation (irradiation and non-irradiation).

General ANOVA was used to analyse treatment effects for weight loss in Sections 3.3.3.2, 3.3.3.3

and 3.3.4.2. The factors in Section 3.3.3.2 were irradiation (irradiation and non-irradiation) and

bagging (no bag, polyethylene bag, polyethylene bag with nitrogen flushing, macro-perforated bag,

macro-perforated bag with high RH and paper bag) for weight loss on days 8 and 10, respectively.

The factors in Section 3.3.3.3 were, fruit ripeness stage (hard, sprung and rubbery), irradiation

(irradiation and non-irradiation) and bagging (no bag, polyethylene bag and polyethylene bag with

nitrogen flushing) for weight loss on days 8 and 12, respectively. The factors in Section 3.3.4.2 fruit

ripeness stage (hard, sprung and rubbery) and irradiation (irradiation and non-irradiation) for weight

loss on days 1 and 4. General ANOVA was used in statistical analyses of titratable acidity and

soluble solids concentration at eating ripe by factors of irradiation (irradiation and non-irradiation)

and waxing (distilled water and one layer of 75% carnauba wax) in Section 3.3.2.2. General

ANOVA was used in statistical analyses of LD and skin colour at eating ripe in Section 3.3.4.1 by

factors of factors of fruit ripeness stage (hard, sprung and rubbery) and irradiation (irradiation and

non-irradiation). General ANOVA was used in statistical analyses of LD, skin colour, titratable

acidity and soluble solids concentration at eating ripe in Section 3.3.4.2 by factors of fruit ripeness

68

stage (hard, sprung and rubbery) and irradiation (irradiation and non-irradiation). The significance

of differences between treatments was tested using the protected Fisher‘s LSD test at the 5% level.

All statistical analyses were conducted in GenStat (2013) statistical software.

3.3 Results

3.3.1 Experiment 1. Effects of chemicals

3.3.1.1 Effects of citric acid and ascorbic acid in the 2011 – 12 season

A highly significant (P < 0.001) interaction of time and irradiation was found for LD development

on ‗B74‘ mango fruit (Figure 3.5 A). LD on non-irradiated fruit increased at higher rates than did

LD of irradiated fruit from day 10 to 14, the day fruit became over-ripe. However, at any time from

day 1 to 10, LD on irradiated fruit was significantly (P < 0.05) higher than LD on non-irradiated

fruit. Any interaction of chemicals and other factors such as time and irradiation were found to not

significantly (P < 0.05) affect LD (Table A 1.2).

A significant (P = 0.018) interaction of irradiation and chemicals was found for skin browning

(Figure 3.5 B). Skin browning on irradiated and non-irradiated fruit varied in response to different

chemical treatments. Irradiated fruit had significantly (P < 0.05) higher skin browning than did the

non-irradiated fruit except for the treatment of 100 mM citric acid.

69

Two significant (P < 0.05) interactions of time and irradiation and of irradiation and chemicals were

found for skin colour (Figure 3.6). In the significant (P < 0.001) interaction of time and irradiation,

the trends for skin colour of irradiated and non-irradiated fruit were different across sequential times

(Figure 3.6 A). Skin colour of irradiated fruit increased from day 4, whereas the skin colour of non-

irradiated fruit increased from day 1 (Figure 3.6 A). Irradiated fruit exhibited significantly (P < 0.05)

lower skin colour than non-irradiated fruit on days 5 and 10 but not on day 14. In the significant (P

= 0.003) interaction of irradiation and chemicals, skin colour of irradiated and non-irradiated fruit

varied according to the different chemical treatments (Figure 3.6 B). Skin colour decreased with

increasing concentrations of ascorbic acid for irradiated and non-irradiated fruit. Skin colour

decreased with increasing concentrations of citric acid for non-irradiated fruit, but it increased with

increasing concentrations of citric acid for irradiated fruit. Irradiated fruit with chemicals had

significantly (P < 0.05) lower skin colour than non-irradiated fruit those except those treated with

500 mM citric acid.

Figure 3.5 A: A significant (P < 0.001) interaction of time and irradiation for LD (n = 25). B: A

significant (P = 0.018) interaction of chemicals and irradiation for skin browning (n = 25). 100AA

= 100 mM ascorbic acid, 100CA = 100 mM citric acid, 500AA = 500 mM ascorbic acid, 500CA =

500 mM citric acid, DW = distilled water. ‗B74‘ mango fruit from Southeast Queensland in the

2011 – 12 season were dipped into 100 or 500 mM, citric acid or ascorbic acid and subsequently

exposed to irradiation or not. Fruit treated with distilled water were the controls. More details are

presented in Table A 1.2 and Table A 1.3.

Time from chemicals and irradiation treatments (days)

0 2 4 6 8 10 12 14

LD

( 0

- 5

)

0

1

2

3

4

5No irradiation

Irradiation

LSDLSD = 0.51

Chemicals

100AA 100CA 500AA 500CA DW

Skin

bro

wnin

g (

0 -

5)

0

1

2

3

4

5Irradiation

No irradiation

A B

70

Two significant (P < 0.05) interactions of time and irradiation and of time and chemicals were

found for fruit firmness. In the significant (P < 0.001) interaction of time and irradiation, the pattern

of firmness of irradiated and non-irradiated fruit across sequential times are significantly (P < 0.001)

different, in which two trends crossed over (Figure 3.7 A). However, the differences between

irradiation and non-irradiation treatments at any time were minor (Figure 3.7 A). In the significant

(P = 0.013) interaction of time and chemicals, the firmness of fruit treated with any chemical

increased over time with the same trend except for fruit treated with 500 mM ascorbic acid (Figure

3.7 B).

Figure 3.6 A: A significant (P < 0.001) interaction of γ-irradiation and time on skin colour (n = 25).

B: A significant (P = 0.003) interaction of chemicals and irradiation on skin colour (n = 40). 100AA

= 100 mM ascorbic acid, 100CA = 100 mM citric acid, 500AA = 500 mM ascorbic acid, 500CA =

500 mM citric acid, DW = distilled water. ‗B74‘ mango fruit from Southeast Queensland in the

2011 – 12 season were dipped into 100 or 500 mM, citric acid or ascorbic acid and subsequently

exposed to irradiation or not. Fruit treated with distilled water were the controls. More details are

presented in Table A 1.2.

A B

Time from chemicals

and irradiation treatments (days)

0 2 4 6 8 10 12 14

Skin

co

lou

r (

0 -

6 )

0

1

2

3

4

5

6

No irradiation

Irradiation

LSD LSD = 0.33

Chemicals

100AA100CA500AA500CA DW

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

Irradiation

No irradiation

71

3.3.1.2 Effects of ascorbic acid, calcium chloride and calcium ascorbate in the 2012 – 13 season

A significant (P = 0.009) interaction of time, irradiation and chemicals was found for LD. LD on

non-irradiated and irradiated fruit increased with different trends across sequential times depending

upon the chemical treatments (Figure 3.8 A). LD on irradiated fruit increased at higher rates than

LD on non-irradiated fruit for the first 4 days. LD on fruit exposed to irradiation were significantly

(P < 0.05) higher than that for non-irradiated fruit at any time from day 1 to 11. Although LD on

fruit treated with chemicals and exposed to irradiation or non-irradiation treatments increased

differently, the differences between chemical treatments in irradiation or non-irradiation treatments

were not significant (P < 0.05).

A significant (P < 0.001) interaction of time, γ-irradiation and chemicals was also found for skin

browning (Figure 3.8 B). Skin browning increased with different trends across different times

Figure 3.7 A: A significant (P < 0.001) interaction of irradiation and time on firmness (n = 25).

B: A significant (P = 0.013) interaction of chemicals and time on firmness (n = 10). ‗B74‘ mango

fruit from Southeast Queensland in the 2011 – 12 season were dipped into 100 or 500 mM, citric

acid or ascorbic acid, and subsequently exposed to irradiation or not. Fruit treated with distilled

water were the controls. More details are presented in Table A 1.3.


0 2 4 6 8 10 12 14

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

No irradiation

Irradiation

LSD

0 2 4 6 8 10 12 14

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

DW (control)

100 mM Ascorbic acid

100 mM Citric acid

500 mM Ascorbic acid

500 mM Citric acid

LSD

A B

72

depending upon the chemicals and irradiation treatments. Skin browning on fruit exposed to

irradiation increased at higher rates than did skin browning of non-irradiated fruit from day 0 to 4.

In irradiation treatments, skin browning on fruit treated with 100 mM ascorbic acid, and 100, 50

and 10 mM calcium ascorbate increased at higher rates than did skin browning on control and

treatment with 100 mM calcium chloride from day 0 to 4. Fruit treated with chemicals, except for

calcium chloride, displayed significantly (P < 0.05) higher skin browning than control fruit at any

time from day 4. In non-irradiation treatments, skin browning on fruit treated with 100 mM ascorbic

acid, 100 and 50 mM calcium ascorbate increased at higher rates than did skin browning on controls,

treated with 100 mM calcium chloride and 10 mM calcium ascorbate. All fruit treated with

chemicals except any concentration of calcium ascorbate and 100 mM calcium chloride, exhibited

significantly (P < 0.05) higher skin browning than the control at any time from day 4 onwards.

73

3.3.2 Experiment 2. Effects of waxing

3.3.2.1 Effects of carnauba wax concentration in the 2011 – 12 season

Two significant (P < 0.05) interactions of time and concentration of wax, and of time and

irradiation were found for LD (Figure 3.9 A and B). In the significant (P = 0.024) interaction of

time and concentration of wax, LD on non-irradiated and irradiated fruit increased with different

trends across sequential times depending on the different wax concentrations (Figure 3.9 A).

However, the different concentrations only had minor effects on LD at any time. In the significant

(P < 0.001) interaction of time and irradiation, LD on irradiated and non-irradiated fruit increased

with different trends during ripening (Figure 3.9 B). LD on irradiated fruit increased to higher levels

Figure 3.8 A significant interaction of chemicals, irradiation and time for LD (A) (P = 0.009) and

skin colour (B) (P < 0.001) (n = 15). ‗B74‘ mango fruit from Southeast Queensland in the 2012 –

13 season were dipped in 100 mM calcium chloride, ascorbic acid or calcium ascorbate, 10 or 50

mM calcium ascorbate, and subsequently exposed to either irradiation or not. Fruit treated with DW

(distilled water) were the controls. More details are presented in Table A 1.4.

0 2 4 6 8 10 12

LD

(0

- 5

)

0

1

2

3

4

5 LSD


0 2 4 6 8 10 12

Sk

in b

row

nin

g (

0 -

5)

0

1

2

3

4

5

DW (control), no irradiation

100 mM Calcium chloride, no irradiation

100 mM Ascorbic acid, no irradiation

10 mM Calcium ascorbate, no irradiation



DW (control), irradiation

100 mM Calcium chloride, irradiation

100 mM Ascorbic acid, irradiation

10 mM Calcium ascorbate, irradiation



LSD

A B

74

than did LD on non-irradiated fruit from day 3 to 7. Irradiated fruit had significantly (P < 0.05)

higher LD than non-irradiated fruit at any time from day 3 to 11.

Two significant (P < 0.05) interactions of time and concentration of wax (Figure 3.9 C) and of time

and irradiation (Figure 3.9 D) were found for skin colour. In the significant (P = 0.006) interaction

of time and concentration of wax, skin colour of fruit treated with different concentrations of wax

increased with different trends across sequential times (Figure 3.9 C). Skin colour of fruit treated

with 80% carnauba wax increased at lower rates than did skin colour of fruit treated with other

treatments from day 3 to 7. Fruit treated with 80% carnauba wax had significantly (P < 0.05) lower

skin colour than control fruit at any time from day 3 to 10. In the significant (P < 0.001) interaction

of time and irradiation, skin colour of non-irradiated fruit increased at higher rates than did skin

colour of irradiated fruit from day 3 to 7 (Figure 3.9 D). Non-irradiated fruit had significantly (P <

0.05) greater skin colour than irradiated fruit on days 7 and 11.

75

Figure 3.9 A and C: A significant (P = 0.024; P = 0.006) interaction of concentration of wax and

time for LD (A) and skin colour (C) (n = 20). B and D: A significant (P < 0.001; P < 0.001)

interaction of irradiation and time for LD (B) and skin colour (D) (n = 50). ‗B74‘ mango fruit from

Southeast Queensland in the 2011 – 12 season were dipped into 10, 20, 40 or 80% carnauba wax,

and subsequently exposed to either irradiation or not. Fruit treated with DW (distilled water) were

the controls. More details are presented in Table A 1.5 and Table A 1.6.

A significant (P = 0.001) interaction of time and concentration of wax was found for fruit firmness

(Figure 3.10). Firmness of fruit treated with different concentrations of wax increased with different

trends over time, in which the trends crossed over. However, the differences between different

concentrations of wax were minor at any time.

LD

( 0

- 5

)

0

1

2

3

4

5LSD

LD

( 0

- 5

)

0

1

2

3

4

5LSD

Time from waxing and irradiation treatments (days)

0 2 4 6 8 10 12

Skin

colo

ur

( 0 -

6 )

0

1

2

3

4

5

6

DW (control)

10% Wax

20% Wax

40% Wax

80% Wax

LSD

0 2 4 6 8 10 12

Skin

colo

ur

( 0 -

6 )

0

1

2

3

4

5

6

No irradiation

Irradiation

LSD

C D

A B

A and C B and D

76

3.3.2.2 Effects of multiple coatings of 75% carnauba wax in the 2012 – 13 season

A significant (P < 0.001) interaction of time, irradiation and layers of wax was found for LD

(Figure 3.11 A). LD on fruit treated in this experiment increased with different trends across

different times. LD on irradiated fruit treated with three layers of wax increased at lower rates than

did LD on irradiated control fruit from day 0 to 4. From day 4 to 14, LD of fruit with three layers of

wax increased at higher rates than did LD of control fruit in irradiation treatments not non-

irradiation treatments. Irradiated fruit treated with three layers of wax exhibited significantly (P <

0.05) lower LD than irradiated control fruit at any time from day 4 to 14. Non-irradiated fruit

treated with three layers of wax developed similar levels of LD as non-irradiated fruit treated with

one layer of wax and non-irradiated control fruit at any time from day 4 to 14.

A significant (P = 0.048) interaction of time, irradiation and layers of wax was found for skin

colour (Figure 3.11 B). Skin colour of non-irradiated and irradiated fruit increased with different

trends across sequential times depending upon the layers of wax treatments. Skin colour of

irradiated control fruit increased at lower rates from day 0 to 8 and at higher rates from day 8 to 14

than skin colour of non-irradiated control fruit. Skin colour of irradiated control fruit was

Figure 3.10 A significant (P < 0.001) interaction of concentration of wax and time for firmness (n =

20). ‗B74‘ mango fruit from Southeast Queensland in the 2011 – 12 season were dipped into 10, 20,

40 or 80% carnauba wax, and subsequently exposed to either irradiation or not. Fruit treated with

DW (distilled water) were the controls. More details are presented in Table A 1.7.


0 2 4 6 8 10 12

Fir

mnes

s (

0 -

4 )

0

1

2

3

4

DW (control)

10% Wax

20% Wax

40% Wax

80% Wax

LSD

77

significantly lower than that of non-irradiated control fruit on day 8 but not at other times. Skin

colour of fruit treated with three layers of wax increased at lower rates than skin colour of fruit

treated with one layer of wax and control fruit across sequential times. Skin colour of fruit with

three layers of wax was significantly (P < 0.05) lower than skin colour of fruit with one layer of

wax and control fruit in non-irradiation treatments at any time from day 8 and in irradiation

treatments at any time from day 11.

A significant (P < 0.001) interaction of time and layers of wax was found for firmness (Figure 3.11

C). Firmness of fruit with no wax, one, and three layers of wax increased with different trends.

Firmness of control fruit obviously increased from day 4, firmness of fruit with one layer of wax

obviously increased from day 8 and firmness of fruit with three layers of wax obviously increased

from day 11. Fruit with three layers of wax had significantly (P < 0.05) lower firmness than fruit

with one layer of wax and then control fruit at any time from day 8.

A significant (P < 0.001) interaction of time, layers of wax and irradiation was found for weight

loss (Figure 3.11 D). Weight loss of fruit with one and three layers of wax increased to lower levels

than weight loss of control fruit across sequential times. Weight loss of fruit with one and three

layers of wax was significantly (P < 0.05) lower than weight loss of control fruit. Although

irradiated control fruit and fruit with three layers of wax had higher weight loss than the matching

sets of non-irradiated fruit, the differences between non-irradiated and irradiated treatments of

weight loss were not significant (P < 0.05) at any time from day 4.

78

A significant (P = 0.01) interaction of wax and irradiation was found for fruit TA at eating ripe

(Table 3.2). The TA of fruit treated with one layer of wax and control fruit response prior to

irradiation and non-irradiation were different at eating ripe. Irradiated control fruit exhibited

Figure 3.11 A: A significant (P < 0.001) interaction of layers of wax, irradiation and time for LD (n

= 15) (A); B: A significant (P = 0.048) interaction of layers of wax, irradiation and time for skin

colour (n = 15). C: A significant (P < 0.001) interaction of layers of wax and time for firmness (n =

30). D: A significant (P < 0.001) interaction of time, layers of wax and irradiation for weight loss (n

= 15). ‗B74‘ mango fruit from Southeast Queensland in the 2012 – 13 season were dipped once or

three times into 75% carnauba wax for 10 s and subsequently and then experienced with either

irradiation or not. Fruit treated with DW (distilled water) were the controls. More details are

presented in Table A 1.8 and Table A 1.9.

LD

(0

- 5

)

0

1

2

3

4

5

LSD

LSD

A B

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6


0 2 4 6 8 10 12 14

Fir

mn

ess

(0 -

4)

0

1

2

3

4

DW (control)

1 Layer of 75% carnauba wax

3 Layers of 75% carnauba wax

LSD

0 2 4 6 8 10 12 14

Wei

ght

loss

(%

)

0

1

2

3

4

5

DW (control), no irradiation

1 Layer of 75% carnauba wax, no irradiation

3 Layers of 75% carnauba wax, no Irradiation

DW (control), irradiation

1 Layer of 75% carnauba wax, irradiation

3 Layers of 75% carnauba wax, irradiation

LSD

C D

A, B and D C

79

significantly (P < 0.05) higher TA levels than fruit treated with one layer of wax. No significant (P

= 0.05) effects were observed on fruit soluble solids concentration at eating ripe.

3.3.3 Experiment 3. Effects of bagging

3.3.3.1 Effects of polyethylene bagging in the 2011 – 12 season

A significant (P < 0.001) interaction of time, irradiation and bagging was found for LD (Figure 3.12

A). LD on irradiated and non-irradiated fruit increased with different trends across sequential times

depending upon the bagging treatments. Non-irradiated and irradiated fruit enclosed in polyethylene

bags with nitrogen had similar levels of LD as non-irradiated and irradiated fruit maintained in

polyethylene bags without nitrogen, respectively. LD on the irradiated control fruit increased with

the similar trend as did LD on the non-irradiated control fruit across sequential times. However, the

LD on the irradiated control fruit was significantly (P < 0.05) higher than the LD on the non-

Table 3.2 A significant (P = 0.01) interaction of layers of 75% carnauba wax and γ-irradiation on

titratable acidity (%) at eating ripe (n = 10). ‗B74‘ mango fruit from Southeast Queensland in the

2012 – 13 season were dipped once into 75% carnauba wax for 10 s and then experienced with

either irradiation or not. Fruit treated with DW (distilled water) were the controls. Data are

expressed as means and those followed by the same letters are not significant at P = 0.05 according

to the Fisher Protected test. More details are presented in Table A 1.10.

Factors Titratable acidity (%)

Irradiation × layers of wax

DW (control), no irradiation 0.12 a

One layer of wax, no irradiation 0.11 a

DW (control), irradiation 0.17 b

One layer of wax, irradiation 0.13 a

General Factorial ANOVA

Irradiation ***

Layers of wax **

Irradiation × layers of wax **

*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant (P <

0.001); NS: not significant.

80

irradiated control fruit at any time from day 3. LD on irradiated fruit held in polyethylene bags for

48 h increased at higher rates than did LD on irradiated fruit enclosed in polyethylene bags for 24 h

and irradiated control fruit from day 3 to 7. The irradiated fruit enclosed in polyethylene bags for 48

h displayed significantly (P < 0.05) lower LD than the irradiated fruit maintained in polyethylene

bags for 24 h and irradiated control fruit on day 3 (one and two days after removing bags as for the

fruit treated with 48 and 24 h, respectively). However, similar levels of LD were found for all

irradiated fruit treated with any bagging treatments on days 7 and 11.

A significant (P < 0.001) interaction of time, irradiation and bagging was found for skin colour

(Figure 3.12 B). Skin colour of irradiated and non-irradiated fruit increased with different trends

across sequential times depending upon the bagging treatments. At any time across sequential times,

non-irradiated and irradiated fruit enclosed in polyethylene bags with nitrogen had similar levels of

skin colour as non-irradiated and irradiated fruit held inside polyethylene bags without nitrogen,

respectively. However, skin colour of irradiated control fruit increased at lower rates from day 3 to

7 and at higher rates from day 7 to 11 than skin colour of non-irradiated control fruit. The skin

colour of irradiated control fruit was lower than the skin colour of non-irradiated fruit on day 7 but

not at other times. Non-irradiated fruit maintained in polyethylene bags for 24 and 48 h increased

skin colour at higher rates than non-irradiated control fruit from day 3 to 7. The skin colour of non-

irradiated fruit enclosed in polyethylene bags for 24 and 48 h was significantly (P < 0.05) lower

than the skin colour of non-irradiated control fruit on day 3 but not on days 7 and 11. Irradiated fruit

enclosed in polyethylene bags for 24 and 48 h increased at similar rates as irradiated control fruit

did. The skin colour of irradiated fruit enclosed in polyethylene bags for 24 and 48 h was

significantly (P < 0.05) lower than skin colour of irradiated control fruit at any time from day 3.

81

A significant (P < 0.001) interaction of time and bagging was found for fruit firmness (Figure 3.13).

The trends of firmness of fruit treated with bagging treatments crossed over across sequential times.

However, the differences between bagging treatments were minor at any time.

Figure 3.12 A: A significant (P < 0.001) interaction of bagging, γ-irradiation and time for LD (n =

15); B: A significant (P < 0.001) interaction of bagging, γ-irradiation and time for skin colour (n =

15). ‗B74‘ mango fruit from Southeast Queensland in the 2011 – 12 season were enclosed in

polyethylene bags with or without nitrogen flushing, and subsequently experienced with irradiation

or not, and finally removed from the bags after 24 and 48 h storage. Fruit with no bag were the

controls. More details are presented in Table A 1.11.

Time from bagging and irradiation treatments (days)

0 2 4 6 8 10 12

LD

( 0

- 5

)

0

1

2

3

4

5

No bagging (control), no irradiation

Bagging, 24 h, no irradiation

Bagging, nitrogen, 24 h, no irradiation

Bagging, 48 h, no irradiation

Bagging, nitrogen, 48 h, no irradiation

No bagging (control), irradiation

Bagging, 24 h, Irradiation

Bagging, nitrogen, 24 h, irradiation

Bagging, 48 h, irradiation

Bagging, nitrogen, 48 h, irradiation

LSD

0 2 4 6 8 10 12

Skin

co

lou

r (

0 -

6 )

0

1

2

3

4

5

6LSD

A B

82

3.3.3.2 Effects of bagging with different types of bags in the 2012 – 13 season

A significant (P < 0.001) interaction of time, irradiation and bagging was found for LD (Figure

3.14 A). LD on non-irradiated and irradiated fruit increased with different trends across sequential

times depending upon the bagging treatments. At any time across sequential times, non-irradiated

and irradiated fruit enclosed in polyethylene bags with nitrogen had similar levels of LD as non-

irradiated and irradiated fruit maintained in polyethylene bags without nitrogen, respectively. At

any time across sequential times, non-irradiated and irradiated fruit held inside macro-perforated

bags with high RH had similar LD as non-irradiated and irradiated fruit enclosed in macro-

perforated bags without high RH. However, LD on the irradiated control increased at higher rates

than did LD on the non-irradiated control fruit across sequential times from day 0 to 8. The LD on

the irradiated control fruit was significantly (P < 0.05) higher than the LD on the non-irradiated

control fruit on days 8 and 10. LD on the irradiated fruit enclosed in polyethylene bags increased at

lower rates than did LD on the irradiated fruit maintained in macro-perforated bags, and irradiated

control fruit from day 0 to 8. The fruit held inside polyethylene bags exhibited significantly (P <

0.05) lower levels of LD as the fruit enclosed in macro-perforated bags on day 8, the day of bags

removals. LD on the irradiated fruit enclosed in polyethylene bags increased at higher rates than did

Figure 3.13 A significant (P < 0.001) interaction of bagging and time for firmness (n = 30). ‗B74‘

mango fruit from Southeast Queensland in the 2011 – 12 season were enclosed in polyethylene bags

with or without nitrogen flushing, and were subsequently exposed to γ-irradiation or not, and finally

removed from bags after 24 or 48 h storage. Fruit with no polyethylene bags were the controls. All

fruit were all kept in the ripening room at 20C and 90% RH. More details are presented in Table A

1.12.

LSD


0 2 4 6 8 10 12

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

No bagging (control)

Bagging, 24 h

Bagging, nitrogen, 24 h

Bagging, 48 h

Bagging, nitrogen, 48 h

83

LD on the irradiated fruit maintained in macro-perforated bags, and on the irradiated control fruit

from day 8 to 10, although LD on the irradiated fruit held inside polyethylene bags was still lower

than LD on the irradiated fruit enclosed in macro-perforated bags, and on the irradiated control fruit

on day 10. Similar levels of LD were found for all irradiated fruit treated with bagging treatments.

A significant (P < 0.001) interaction of time, irradiation and bagging was found for skin colour

(Figure 3.14 B). Skin colour of non-irradiated and irradiated fruit varied according to bagging

treatments across sequential times. At any time across sequential times, non-irradiated and

irradiated fruit enclosed in polyethylene bags with nitrogen had similar levels of skin colour as non-

irradiated and irradiated fruit held inside polyethylene bags without nitrogen, respectively. High RH

in macro-perforated bags did not affect skin colour for irradiated fruit. However, it affected skin

colour for non-irradiated fruit. Skin colour of non-irradiated fruit enclosed in macro-perforated bags

without high RH increased at lower rates from day 0 to 8 and at higher rates from day 8 to 10 than

did the skin colour of non-irradiated fruit enclosed in macro-perforated bags with high RH. The skin

colour of non-irradiated fruit that were maintained in macro-perforated bags without high RH was

significantly (P < 0.05) lower than the skin colour of the non-irradiated fruit enclosed in macro-

perforated bags with high RH on day 8 but not day 10. Skin colour of irradiated control fruit

increased at lower rates than non-irradiated control fruit across sequential times. The skin colour of

irradiated control fruit were significantly (P < 0.05) lower than the skin colour of non-irradiated

control fruit on days 8 and 10. Skin colour of non-irradiated fruit enclosed in polyethylene bags

without nitrogen, and macro-perforated bags without high RH increased at lower rates than skin

colour of non-irradiated fruit enclosed in paper bags and non-irradiated control fruit from day 0 to 8.

The skin colour of non-irradiated fruit maintained in polyethylene bags without nitrogen, and

macro-perforated bags without high RH was significantly (P < 0.05) lower than the skin colour of

non-irradiated fruit kept in paper bags and non-irradiated control fruit on days 8 and 10. Similar

effects of polyethylene bags on reducing skin colour were found for irradiated fruit although the

effects were not markedly.

A significant (P = 0.048) interaction of time, irradiation and bagging was found for fruit firmness

(Figure 3.14 C). At any time across sequential times, non-irradiated and irradiated fruit enclosed in

macro-perforated bags with high RH had similar levels of firmness as non-irradiated and irradiated

fruit held inside macro-perforated bags without high RH, respectively. At any time across

sequential times, non-irradiated and irradiated fruit enclosed in polyethylene bags with nitrogen had

similar firmness as non-irradiated and irradiated fruit maintained in polyethylene bags without

84

nitrogen, respectively. The irradiated control fruit had similar levels of firmness as the non-

irradiated control fruit at any time across sequential times. However, firmness of fruit enclosed in

polyethylene bags increased at lower rates than did firmness of fruit enclosed in macro-perforated

bags and control fruit from day 0 to 8 in irradiation and no irradiation treatments. The fruit

maintained in polyethylene bags had significantly (P < 0.05) lower firmness than the fruit enclosed

in macro-perforated, paper and no bags in irradiation and no irradiation treatments on days 8 and 11.

85

Figure 3.14 A, B and C: A significant (P < 0.001; P < 0.001; P = 0.048) interaction of bagging,

irradiation and time for LD (A), skin colour (B) and firmness (C) (n = 15). ‗B74‘ fruit from

Southeast Queensland collected in the 2012 – 13 season were treated with paper bags, macro-

perforated bags, macro-perforated bags with high RH, polyethylene bags, or polyethylene bags with

nitrogen flushing, and subsequently experienced with either irradiation or not. Fruit not bagged

were the controls. Day 0 is the day of bagging and γ-irradiation treatment. Day 8 is the day of bags

removal. Data on day 0 are the quality parameters of fruit before they were bagged and irradiated.

Data on day 8 are the quality parameters of fruit after bags were removed from them. More details

are presented in Table A 1.13 and Table A 1.14.

LD

( 0

- 5

)

0

1

2

3

4

5

No bagging (control), no irradiation Paper bagging, no irradiation Macro-perforated bagging, no high humidity, no irradiation Macro-perforated bagging, high humidity, no irradiation Polyethylene bagging, no nitrogen, no irradiation Polyethylene bagging, nitrogen, no irradiation No bagging (control), irradiation Paper bagging, irradiation Macro-perforated bagging, no high humidity, irradiation Macro-perforated bagging, high humidity, irradiation Polyethylene bagging, no nitrogen, irradiation Polyethylene bagging, nitrogen, irradiation

LSD

Sk

in c

olo

ur

( 0

- 6

)

0

1

2

3

4

5

6LSD

A B


0 2 4 6 8 10

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

C

LSD

86

Fruit treated with different types of bags response for irradiation on weight loss were significantly

(P < 0.001) different on day 8. On day 8, irradiated fruit enclosed in paper, polyethylene bags with

and without nitrogen flushing exhibited higher weight loss than non-irradiated fruit (Figure 3.15).

The fruit enclosed in macro-perforated, polyethylene and paper bags exhibited lower weight loss

than the control fruit in irradiation and no irradiation treatments on day 8 (Figure 3.15). The similar

significant (P = 0.009) effects of different types of bags were found on weight loss on day 10.

87

Figure 3.15 A significant (P < 0.001; P = 0.009) interaction of bagging and γ-irradiation for weight

loss on days 8 and 10, respectively (n = 15). ‗B74‘ fruit from Southeast Queensland collected in the

2012 – 13 season were treated with paper bags, macro-perforated bags, macro-perforated bags with

high RH, polyethylene bags, or polyethylene bags with nitrogen flushing and subsequently

experienced with either irradiation or not. Fruit not bagged were the controls. Day 0 is the day of

bagging and γ-irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the quality

parameters of fruit before they were bagged and irradiated. Data on day 8 are the quality parameters

of fruit after bags were removed from them. More details are presented in Table A 1.14. LSD1 is the

least significant difference for data on day 8 and LSD2 is the least significant difference for data on

day 10.

3.3.3.3 Effects of polyethylene bagging if fruit at different ripeness stages in the 2013 – 14 season

Three significant (P < 0.05) interactions were found for LD, which are the interaction of time,

ripeness and γ-irradiation (P = 0.024), the interaction of time, ripeness and bagging (P = 0.001), and


7 8 9 10 11

Wei

gh

t lo

ss (

%)

0

1

2

3

4

5

No bag, No irradiation P, No irradiation MAP, No high humidity, No irradiationMAP, High humidity, No irradiationPE, No nitrogen, No irradiationPE, Nitrogen, No irradiation No bag, IrradiationP, Irradiation MAP, No high humidity, IrradiationMAP, High humidity, IrradiationPE, No nitrogen, Irradiation PE, Nitrogen, Irradiation

LSD1 = 0.1054

LSD2 = 0.1260

88

the interaction of time, bagging and γ-irradiation (P < 0.001) (Figure 3.16). In the significant (P =

0.024) interaction of time, fruit ripeness stage and γ-irradiation, LD on irradiated and non-irradiated

fruit at different ripeness stages increased with different trends across sequential times (Figure 3.16

A). LD on irradiated fruit increased at higher rates than did LD on non-irradiated fruit from day 0 to

10. LD that developed on fruit that were irradiated at the hard and sprung firmness stages was

significantly (P < 0.05) higher than LD on matching sets of non-irradiated fruit on day 8 and 10,

respectively, while LD on fruit irradiated at a rubbery firmness was significantly (P < 0.05) higher

than LD on non-irradiated rubbery fruit on day 10 but not day 8. In addition, irradiated fruit at three

ripeness stages exhibited similar levels of LD at any time, and non-irradiated sprung fruit exhibited

significantly (P < 0.05) higher LD than non-irradiated hard and rubbery fruit on day 10.

In the significant (P = 0.001) interaction of time, fruit ripeness stage and bagging, LD on fruit at

different ripeness stages increased with different trends across sequential times depending upon

bagging treatments (Figure 3.16 B). The inclusion of nitrogen gas in polyethylene bags did not

affect LD for the three ripeness stages of fruit. LD on control fruit increased at higher rates than did

LD on fruit enclosed in polyethylene bags for any ripeness stage from day 0 to 8. The fruit enclosed

in polyethylene bags exhibited significantly (P < 0.05) lower LD than the control fruit on day 8.

However, LD on fruit maintained in polyethylene bags increased at higher rates than did LD on

control fruit from day 8 to 12. Similar levels of LD were found for all treatments on day 12. No

significant differences between three ripeness stages of fruit treated with any bagging treatment on

LD were found at any time. In the interaction of time, bagging and γ-irradiation (P < 0.001), LD on

irradiated and non-irradiated fruit varied according to fruit ripeness stage across different times

(Figure 3.16 C). The addition of nitrogen in polyethylene bags did not affect LD. LD on irradiated

control fruit increased at higher rates than did LD on non-irradiated control fruit from day 0 to 8.

The LD on irradiated control fruit was significantly (P < 0.05) higher than the LD of non-irradiated

fruit on days 8 and 12. Fruit enclosed in polyethylene bags increased at lower rates than control fruit

from day 0 to 8. The fruit held in polyethylene bags exhibited significantly (P < 0.05) lower LD

than the control fruit on day 8. However, LD on irradiated fruit enclosed in polyethylene bags

increased at higher rates than LD on non-irradiated fruit maintained in polyethylene bags from day

8 to 12, although the LD of irradiated fruit held in polyethylene bags was still lower than the LD of

non-irradiated fruit enclosed in polyethylene bags on day 12.

89

Figure 3.16 A: A significant (P = 0.024) interaction of fruit ripeness stage, γ-irradiation and time for

LD (n = 30). B: A significant (P = 0.001) interaction of fruit ripeness stage, bagging and time for

LD (n = 20). C: A significant (P < 0.001) interaction of bagging, γ-irradiation and time for LD (n =

30). ‗B74‘ mango fruit from Southeast Queensland collected in the 2013 – 14 season reached to

hard, rubbery and sprung after 0, 3 and 8 days. The fruit were then treated with polyethylene bags

with or without nitrogen flushing. Fruit that were not bagged were the controls. All fruit were

subsequently exposed to either γ-irradiation or not. Day 0 is the day of bagging and γ-irradiation

treatment. Day 8 is the day of bags removal. Data on day 0 are the quality parameters of fruit before

they were bagged and irradiated. Data on day 8 are the quality parameters of fruit after bags were

removed from them. More details are presented in Table A 1.15.

B

C


0 2 4 6 8 10 12

0

1

2

3

4

5


Bagging, no irradiation

Bagging, nitrogen, no irradiation


Bagging, irradiation

Bagging, nitrogen, irradiation

LSD

A

LSD

0

1

2

3

4

5Hard, no irradiation

Rubbery, no irradiation

Sprung, no irradiation

Hard, irradiation

Rubbery, irradiation

Sprung, irradiation

LSD

LD

( 0

-5

)

0

1

2

3

4

5 Hard, no bagging (control)

Rubbery, no bagging (control)

Sprung, no bagging (control)

Hard, bagging

Rubbery, bagging

Sprung, bagging

Hard, bagging, nitrogen

Rubbery, bagging, nitrogen

Sprung, bagging, nitrogen

90

Three significant (P < 0.05) interactions were found for skin colour which are the interaction of

time, fruit ripeness stage and irradiation (P < 0.001), the interaction of time, fruit ripeness stage and

bagging (P = 0.007), and the interaction of time, bagging and irradiation (P < 0.001) (Figure 3.17).

In the significant (P < 0.001) interaction of time, fruit ripeness stage and irradiation, skin colour of

non-irradiated and irradiated fruit at different ripeness stages increased with different trends across

sequential times (Figure 3.17 A). Skin colour of irradiated hard fruit increased at higher rates than

did skin colour of non-irradiated hard fruit from day 8 to 12. On day 12, irradiated hard fruit

showed significantly (P < 0.05) lower skin colour than non-irradiated hard fruit. No significant (P <

0.05) differences on skin colour were found between irradiated and non-irradiated treatments for

any sprung and rubbery stage.

In the significant (P = 0.007) interaction of time, fruit ripeness stage and bagging, skin colour of

three ripeness stages of fruit increased skin colour with different trends across different times

according to the bagging treatments (Figure 3.17 B). The inclusion of nitrogen in polyethylene bags

did not affect skin colour for any ripeness stage of fruit. Skin colour of fruit enclosed in

polyethylene bags increased at lower rates than did skin colour of control fruit from day 0 to 8 for

any ripeness stage of fruit. Fruit maintained in polyethylene bags displayed significantly (P < 0.05)

lower skin colour than control fruit on day 8 for any ripeness stage of fruit. Rubbery fruit had the

first high skin colour and then sprung fruit and finally hard fruit. In the interaction of time, bagging

and irradiation (P < 0.001), skin colour of non-irradiated and irradiated fruit enclosed in

polyethylene bags with and without nitrogen increased with different trends across sequential times

(Figure 3.17 C). Flushing polyethylene bag with nitrogen did not affect skin colour for any ripeness

stage of fruit. Skin colour of irradiated fruit enclosed in polyethylene bags increased at lower rates

than did skin colour of irradiated control fruit from day 0 to 8. Fruit enclosed in polyethylene bags

displayed significantly (P < 0.05) lower skin colour than non-irradiated control fruit on days 8 and

12.

91

Figure 3.17 A: A significant (P < 0.001) interaction of fruit ripeness stage, γ-irradiation and time for

skin colour (n = 30). B: A significant (P = 0.007) interaction of fruit ripeness stage, bagging and

time for skin colour (n = 20). C: A significant (P < 0.001) interaction of bagging, γ-irradiation and

time for skin colour (n = 30). ‗B74‘ mango fruit from Southeast Queensland collected in the 2013 –

14 season reached hard, rubbery and sprung after 0, 3 and 8 days. The fruit were then treated with

polyethylene bags with or without nitrogen flushing. Fruit that were not bagged were the controls.

All the fruit were subsequently exposed to either γ-irradiation or not. Day 0 is the day of bagging

and γ-irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the quality

parameters of fruit before they were bagged and irradiated. Data on day 8 are the quality parameters

of fruit after bags were removed. More details are presented in Table A 1.15.

0

1

2

3

4

5

6Hard, no irradiation



Hard, irradiation


Sprung, irradiation

LSD

LSD


0 2 4 6 8 10 12

0

1

2

3

4

5

6


Bagging, no irradiation

Bagging, nitrogen, no irradiation


Bagging, irradiation

Bagging, nitrogen, irradiation

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6Hard, no bagging (control)



Hard, bagging

Rubbery, bagging

Sprung, bagging




A

B

C

92

The stage of fruit ripeness was based on firmness, in which the subjective firmness scores of hard,

rubbery and sprung fruit were 0, 1 and 2, respectively. One interaction of time, fruit ripeness stage

and irradiation was nearly significant (P = 0.05). Firmness of non-irradiated and irradiated fruit of

different ripeness stages increased with different trends across sequential times (Figure 3.18 A).

However, the differences between the treatments were minor at any time. Another significant (P =

0.001) interaction of time, fruit ripeness stage and bagging was found for firmness (Figure 3.18 B).

In the significant (P = 0.001) interaction of time, fruit ripeness stage and bagging, firmness of fruit

of different ripeness stages enclosed in polyethylene bags with and without nitrogen, and no bags

increased with different trends across sequential times. The inclusion of nitrogen in polyethylene

bags did not affect fruit firmness. Polyethylene bags did not significantly (P < 0.05) affect firmness

for rubbery and sprung fruit. However, hard fruit enclosed in polyethylene bags increased firmness

in lower rates than hard control fruit from day 0 to 8. Hard fruit enclosed in polyethylene bags had

significantly (P < 0.05) lower firmness than hard control fruit on days 8 and 12.

93

Figure 3.18 A: A nearly significant (P = 0.05) interaction of fruit ripeness stage, γ-irradiation and

time for firmness (n = 30). B: A significant (P = 0.001) interaction of fruit ripeness stage, bagging

and time for firmness (n = 20). ‗B74‘ mango fruit from Southeast Queensland collected in the

2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8 days and then treated with

polyethylene bags with or without nitrogen flushing. Fruit that were not bagged were the controls.

All the fruit were subsequently exposed to either γ-irradiation or not. Day 0 is the day of bagging

and γ-irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the quality



Fruit response for different types of bags for weight loss was significantly (P = 0.011) different on

day 8. Fruit enclosed in polyethylene bags displayed lower weight loss than control fruit for any

ripeness stage on day 8 (Figure 3.19 A). The similar significant (P = 0.002) effects of different

types of bags on weight loss of fruit were found on day 10 (Figure 3.19 A). Fruit response for

irradiation for weight loss were significantly (P < 0.001) different on day 8. Irradiated fruit

exhibited higher weight loss than non-irradiated fruit on day 8 (Figure 3.19 B). The similar

0 2 4 6 8 10 12

Fir

mness

(0 -

4)

0

1

2

3

4

Hard, no irradiation



Hard, irradiation


Sprung, irradiation

LSD


0 2 4 6 8 10 12

Fir

mness

( 0

- 4

)

0

1

2

3

4

Hard, no bagging (control)



Hard, bagging

Rubbery, bagging

Sprung, bagging




LSD

A B

94

significant (P < 0.001) effects of irradiation on weight loss of fruit were found on day 10 (Figure

3.19 B).

Figure 3.19 Significant (P = 0.011; P = 0.002) interactions of fruit ripeness stage and bagging for

weight loss on day 8 and 10 (n = 10). B: Significant (P < 0.001; P < 0.001) effects of γ-irradiation

for weight loss on day 8 and 10 (n = 90). ‗B74‘ mango fruit from Southeast Queensland collected in

the 2013 – 14 season reached to hard, rubbery and sprung after 0, 3 and 8 days. They were then

treated with polyethylene bags with or without nitrogen flushing. The fruit that were not bagged

were the controls. All the fruit were subsequently exposed to either γ-irradiation or not. Day 0 is the

day of bagging and γ-irradiation treatment. Day 8 is the day of bags removal. Data on day 0 are the

quality parameters of fruit before they were bagged and irradiated. Data on day 8 are the quality


0

1

2

3

4

5 Hard, No baggingRubbery, No bagging Sprung, No bagging Hard, Bagging Rubbery, Bagging Sprung, Bagging Hard, Bagging, NitrogenRubbery, Bagging, Nitrogen Sprung, Bagging, Nitrogen

LSD1 = 0.1810

LSD2 = 0.2906

LSD1 = 0.0854

LSD2 = 0.1370


6 8 10 12 14

Wei

gh

t lo

ss (

%)

0

1

2

3

4

5

No irradiationIrradiation

95

3.3.4 Experiment 4. Effects of fruit ripeness stage

3.3.4.1 Effects of fruit ripeness stages grown in Southeast Queensland in the 2013 – 14 season

A significant (P = 0.001) interaction of time, irradiation and fruit ripeness stage was found for LD

(Figure 3.20 A). LD on irradiated fruit increased at higher rates than did LD on matching sets of

non-irradiated fruit from day 0 to 5 for any ripeness stage (Figure 3.20 A). Irradiated fruit exhibited

significantly (P < 0.05) higher LD than non-irradiated fruit at any time from day 3. LD on fruit that

were irradiated at the sprung stage of firmness developed at lower rates than did LD on fruit that

were irradiated at the hard and rubbery stages from day 0 to 5. Fruit that were irradiated at the

sprung firmness stage exhibited significantly (P < 0.05) lower levels of LD as compared to fruit that

were irradiated at hard and rubbery firmness stages at any time from day 1 to 5.

A significant (P < 0.001) interaction of time, γ-irradiation and fruit ripeness stage was found for

skin colour (Figure 3.20 B). Skin colour of fruit that were not irradiated at hard stage increased at

higher rates than did skin colour of fruit that were irradiated at hard stage across sequential times.

Similar levels of skin colour were found on non-irradiated fruit and irradiated rubbery and sprung

fruit at any time. Fruit that were irradiated at the hard firmness stage had significantly (P < 0.05)

lower skin colour than fruit that were not irradiated at the hard firmness on day 12.

A significant (P < 0.001) interaction of time and fruit ripeness stage was found for firmness (Figure

3.20 C). Firmness of different ripeness stages of fruit increased with different trends (Figure 3.20 C).

Sprung fruit exhibited significantly (P < 0.05) higher firmness than rubbery fruit and then hard fruit

at any time (Figure 3.20 C).

A significant (P = 0.011) interaction of time and fruit ripeness stage was found for weight loss

(Figure 3.20 D), in which the trend of weight loss of different ripeness stages of fruit crossed over

(Figure 3.20 D). However, the differences between fruit at three ripeness stages were minor at any

time (Figure 3.20 D).

96

When fruit of the three ripeness stages all reached eating ripe (firmness = 3), a significant (P < 0.05)

interaction of irradiation and ripeness was found for LD and skin colour (Table 3.3). Fruit that were

irradiated at the hard and rubbery stages developed significantly (P < 0.05) higher LD than fruit

irradiated at the sprung stage (Table 3.3). In addition, fruit were irradiated at the sprung stage

developed significantly (P < 0.05) higher skin colour than the rubbery stage followed by the hard

stage (Table 3.3).

Figure 3.20 A and B: A significant (P = 0.001; P < 0.001) interaction of fruit ripeness stage, γ-

irradiation and time for LD (A) and skin colour (B) (n = 10). C: A significant (P < 0.001)

interaction of fruit ripeness stage and time for firmness (n = 20). D: A significant (P = 0.011)

interaction of fruit ripeness stage and time for weight loss (n = 20). ‗B74‘ mango fruit from

Southeast Queensland collected in the 2013 – 14 season reached hard, rubbery and sprung after 0, 3

and 8 days in a ripening room at 20°C and 90 – 100% RH, and were subsequently exposed to either

γ-irradiation or not. More details are presented in Table A 1.16 and Table A 1.17.

LSD LSD

LD

( 0

- 5

)

0

1

2

3

4

5

A B

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

Time from irradiation (days)

0 2 4 6 8 10 12

Fir

mn

ess

(0 -

4)

0

1

2

3

4

0 2 4 6 8 10 12

Wei

gh

t lo

ss (

% )

0

1

2

3

4

5

6LSDLSD

C D

Hard, No irradiation

Rubbery, No irradiation

Sprung, No irradiation

Hard, Irradiation

Rubbery, Irradiation

Sprung, Irradiation

Hard

Rubbery

Sprung

A and B C and D

97

3.3.4.2 Effects of fruit ripeness stage grown in the Northern Territory in the 2013 – 14 season

A significant (P = 0.012) interaction of time, γ-irradiation and fruit ripeness stage was found for LD

(Figure 3.21 A). LD on fruit that were treated with and without irradiation at different ripeness

stages increased with different trends across sequential times (Figure 3.21 A). LD on fruit that were

irradiated at three ripeness stages increased higher than LD on matching sets of non-irradiated fruit

from day 0 to 4 (Figure 3.21 A). LD on irradiated sprung and rubbery fruit increased less than that

of irradiated hard fruit from day 0 to 4. Fruit that were irradiated at the hard firmness stage

developed exhibited significantly (P < 0.05) higher LD than fruit that were irradiated at the rubbery

and sprung stages on days 1 and 4.

A significant (P < 0.001) interaction of fruit ripeness stage and time was found for firmness (Figure

3.21 B). Firmness of sprung and rubbery fruit increased at higher rates than that of hard fruit from

Table 3.3 A significant (P < 0.001; P = 0.001; P = 0.027) interaction of fruit ripeness stage and γ-

irradiation on LD and skin colour at eating ripe (n = 10). ‗B74‘ mango fruit from Southeast

Queensland in the 2013 – 14 season reached hard, rubbery and sprung fruit after 0, 3 and 8 days at

ripening room at 20°C and 90 – 100% RH, respectively, and subsequently exposed to either γ-

irradiation or not. Data are expressed as mean and those followed by the same letters are not

significant different at P = 0.05 according to the Protected Fisher test. More details are presented in

Table A 1.18.

Factors D Skin colour

Fruit ripeness × γ-irradiation

Hard, no irradiation 2.4 a 5.8 c

Rubbery, no irradiation 2.5 a 5.7 c

Sprung, no irradiation 2.3 a 6 c

Hard, irradiation 4.9 c 3.5 a

Rubbery, irradiation 4.6 c 4.6 b

Sprung, irradiation 3.4 b 5.6 c

General Fact rial ANOVA

Irradiation *** ***

Fruit ripeness stage *** ***

Irradiation × fruit ripeness stage *** **


0.001); NS: not significant different.

98

day 0 to 1 but less than from day 1 to 4. Sprung fruit exhibited significantly (P < 0.05) higher

firmness than rubbery fruit and hard fruit at any time.

A significant (P < 0.05) interaction of fruit ripeness stage and irradiation was found for weight loss

on day 1 (P = 0.034) and 4 (P = 0.002) (Figure 3.21 C). Fruit that were not irradiated at rubbery

stage displayed significantly (P < 0.05) higher weight loss than fruit that were not irradiated at hard

stage and fruit that were irradiated at hard stage on day 1. The treatment of fruit that were not

irradiated at rubbery stage had higher weight loss than other treatments except for the treatment of

fruit that were irradiated at rubbery stage (Figure 3.21 C).

99

Figure 3.21 A: A significant (P = 0.012) interaction of time, fruit ripeness stage and γ-irradiation on

LD (n = 10). B. A significant (P < 0.001) interaction of time and fruit ripeness stage on firmness (n

= 20). C. Significant interactions of fruit ripeness stage and irradiation on weight loss (%) on day 1

(P = 0.034) and 4 (P = 0.002) (n = 10). ‗B74‘ fruit in the 2013 – 14 season reached hard, rubbery

and sprung fruit in a ripening room at 20°C and 90 – 100% RH after 0, 5 and 8 days, and

subsequently exposed to either γ-irradiation or not. More details are presented in Table A 1.19.

LD

(0

- 6

)

0

1

2

3

4

5




Hard, irraidation

Rubbery, irraidation

Sprung, irraidation

LSD

Time from irradiation treatments (days)

0 1 2 3 4 5

Fir

mn

ess

(0 -

4)

0

1

2

3

4

Hard

Rubbery

Sprung

A

B

LSD

C


1 4

Wei

gh

t lo

ss (

%)

0

1

2

3




Hard, irradiation


Sprung, irradiation

LSD1 = 0.33

LSD2 = 0.34

100

Two significant (P < 0.05) interactions were found for skin colour, which are the interaction of time

and γ-irradiation (P = 0.050) and the interaction of time and fruit ripeness (P < 0.001) (Figure 3.22).

In the significant (P = 0.050) interaction of time and fruit ripeness, skin colour of hard and rubbery

fruit exhibited greater than that of sprung fruit across sequential times (Figure 3.22 A). In the

significant (P < 0.001) interaction of time and irradiation, the skin colour of irradiated fruit

increased less than that of non-irradiated fruit (Figure 3.22 B). On day 5, the irradiated fruit had

significantly (P < 0.05) lower skin colour than the non-irradiated fruit.

When fruit of different ripeness stages reached eating ripe (firmness = 3), a significant (P < 0.001;

P < 0.001) interaction of γ-irradiation and fruit ripeness stage was found for LD and weight loss

(Table 3.4). Different ripeness stages of fruit responded to irradiation and no irradiation differently,

in terms of LD and weight loss. Three ripeness stages of fruit with non-irradiation showed similar

levels of LD, but the irradiated rubbery and sprung fruit had significantly (P < 0.05) higher LD than

the irradiated hard fruit. Sprung fruit displayed significantly lower weight loss than rubbery fruit

followed by hard fruit in either irradiation or non-irradiation treatments.

Figure 3.22 A: A significant (P < 0.001) interaction of fruit ripenessand time on skin colour (n =

20). B: A significant (P = 0.05) interaction of γ-irradiation and time on skin colour in fruit ripeness

treatments (n = 30). ‗B74‘ mango fruit in the 2013 – 14 season reached hard, rubbery and sprung

fruit after 0, 5 and 8 days in a ripening room at 20°C and 90 – 100% RH, and subsequently exposed

to γ-irradiation or not. More details are presented in Table A 1.19.

0 1 2 3 4 5

Skin

colo

ur

(0 -

6)

0

1

2

3

4

5

6

No irradiation

Irradiation


0 1 2 3 4 5

Skin

colo

ur

(0 -

6)

0

1

2

3

4

5

6

Hard

Rubbery

Sprung

LSD LSD

A B

101

3.4 Discussion

3.4.1 LD

Lenticel discolouration (LD) did not increase significantly until fruit were over-ripe (firmness > 3)

(Figure 3.5 A). In all experiments, LD on ‗B74‘ mango fruit was found to increase immediately

after irradiation. In addition, LD on irradiated fruit were significantly (P < 0.05) higher than that of

non-irradiated fruit at any time except day 0. These findings are in agreement with those of Hofman

et al. (2009) and Joyce et al. (2011). Postharvest treatment of fruit with chemicals (100 and 500 mM

ascorbic acid, 100 and 500 mM citric acid, 10, 50 and 100 mM calcium ascorbate, and 100 mM

calcium chloride) prior to γ-irradiation did not reduce LD on irradiated fruit (Table A 1.2 and Table

A 1.4). To the contrary, treatments with calcium ascorbate and ascorbic acid increased skin

browning that developed on fruit after γ-irradiation (Table A 1.3). The results are different from the

Table 3.4 A significant interaction of irradiation and fruit ripeness stage on LD at eating ripe based

on firmness = 3 (n = 10). ‗B74‘ mango fruit from the Northern Territory in the 2013 – 14 season

reached to hard, rubbery and sprung fruit after 0, 5 and 8 days in a ripening room at 20°C and 90 –

100% RH, and subsequently exposed to either γ-irradiation or not. Data are expressed as mean and

those followed by the same letters are not significant different at P = 0.05 according to the Fisher

Protected test.

Factors LD

Irradiation × fruit ripeness stage

Hard, no irradiation 1.1 a

Rubbery, no irradiation 1.3 a

Sprung, no irradiation 1.3 a

Hard, γ-irradiation 3.3 c

Rubbery, γ-irradiation 2.4 b

Sprung, γ-irradiation 2.0 b

General factorial ANOVA

Irradiatio ***

Fruit ripeness stage **

Irradiation × fruit ripeness stage ***



102

effects of ascorbic acid and calcium ascorbate in reducing browning of fresh-cut apples (Gil et al.,

1998, Aguayo et al., 2010) and fresh-cut eggplants (Barbagallo et al., 2012). The mechanism of

calcium ascorbate effects on increasing skin browning is not clear. The increase in skin browning

caused by treatment of fruit with ascorbic acid might be due to the oxidation of this compound

(Walker, 1995, Guerrero- Beltrán et al., 2005) under irradiation. Another possible cause is that

the concentration of anti-browning chemicals is not within the efficient concentration for fruit

(Rojas-Grau et al., 2009).

Carnauba wax at concentrations from 10 to 80% did not reduce LD on ‗B74‘ mango fruit (Figure

3.9). However, applying three layers of 75% carnauba wax to fruit decreased the level of LD on

irradiated and non-irradiated fruit (Figure 3.11). Unfortunately, these fruit failed to ripen, showing

symptoms of empty and white cavities in the flesh. This is possibly because of anaerobic conditions

created by thick layers of carnauba wax. The maintenance of fruit under elevated nitrogen

atmospheres in polyethylene bag (Figure 3.12, Figure 3.14 and Figure 3.16) and high RH in macro-

perforated bags (Figure 3.14) did not reduce the level of LD that developed on non-irradiated and

irradiated fruit. Polyethylene bagging treatments applied prior to irradiation significantly (P < 0.05)

decreased LD while fruit remained in the bags (Figure 3.12, Figure 3.14 and Figure 3.16). However,

LD increased soon after fruit were removed from the bags (Figure 3.12, Figure 3.14 and Figure 3.16).

Modified atmospheres were created by waxing and bagging for mango fruit (Balwin et al., 1999,

Kader et al., 1989) in these sub-experiments. Similar effects of modified atmosphere packaging in

reducing skin browning by lowering oxygen concentration have been reported on litchi fruit

(Sivakumar and Korsten, 2006) and banana fruit (Nguyen et al., 2004). Therefore, the reduced

oxygen level present inside bagged fruit is the key factor that limited enzymatic browning and

associated LD. It confirms that LD induced by γ-irradiation should be an enzymatic browning.

However, the inclusion of nitrogen in polyethylene bags and high RH in macro-perforated bags did

not affect LD in either irradiation or non-irradiation treatments. Fruit that irradiated at sprung stage

had significantly lower LD than did fruit that irradiated at hard stage for the first 5 days. However,

there were no significant differences between them after then (Figure 3.20). It is interesting to note

that, when fruit at all three ripeness stages tested in the study reached eating ripe, fruit that were

irradiated at the sprung stage exhibited less LD compared to fruit irradiated at the hard stage (Table

3.3 and Table 3.4). Therefore, it can be an alternative promising method reducing LD for ‗B74‘

mango applied in commercial markets. Fruit grown in the Northern Territory and Southeast

Queensland showed the same results (Table 3.3 and Table 3.4). The effects of irradiation on

biochemical levels of different ripeness stages of fruit are presented in Chapter 4.

103

3.4.2 Skin colour

Irradiation delayed the development of yellow skin colour on ‗B74‘ fruit. Similar effects on skin

colour of 1.0 kGy irradiation on ‗Tommy Atkin‘ mango fruit (Sabato et al., 2009), 0.25 kGy

irradiation on ‗Alphonso‘ mango fruit (Dharkar et al., 1966) and 0.2 kGy irradiation on ‗Kensington

Pride‘ mango fruit were observed. It may be that irradiation suppresses the synthesis or activity of

enzyme systems involved in the regulation of chlorophyll breakdown (Boag et al., 1990).

Carnauba wax (80 and 40%), and coating fruit with one and three layers of 75% carnauba wax

delayed skin colour development on ‗B74‘ fruit (Figure 3.9 B and Figure 3.11 B). Similar effects of

carnauba waxing in delaying skin colour have been reported for other mango cultivars including

‗Kensington Pride‘ (Dang et al., 2008). Polyethylene bagging for short durations (such as one [24 h]

and two days [48 h]) significantly reduced skin colour in the first few days but the effects did not

last long after fruit were removed from bags (Figure 3.12 B), which was similar to the effects of

macro-perforated bagging for eight days on skin colour (Figure 3.14 B). However, polyethylene

bagging fruit for a relatively long duration (eight days) significantly decreased skin colour and even

caused the failure of fruit to change skin colour later (Figure 3.14 B). Similar results of modified

atmosphere treatments created by low gas permeability bags in reducing skin colour have been

reported as resulting in decreased synthesis of carotenoids (Ding et al., 2002) and degradation of

chlorophyll (Fonseca et al., 2005). The inclusion of nitrogen in polyethylene bags for short and long

durations did not affect skin colour on ‗B74‘ fruit exposed to either irradiation or non-irradiation

(Figure 3.14 B). The creation of high RH in macro-perforated bags did not influence skin colour on

fruit exposed to irradiation (Figure 3.14 B). However, high RH levels that were maintained in

macro-perforated bags increased skin colour in fruit exposed to non-irradiation treatments while the

fruit was maintained in the bags (Figure 3.14 B). The reason for this treatment response is not

currently clear. Fruit ripeness was closely related to skin colour, in which sprung fruit had an

initially higher skin colour followed by rubbery fruit and hard fruit had a low skin colour (Figure

3.20 B and Figure 3.22 A). Polyethylene bags and γ-irradiation reduced skin colour (less yellow

colour) for hard fruit but not for sprung fruit (Figure 3.17 A). Similar effects of γ-irradiation have

been reported on different ripeness stages of ‗Kensington Pride‘ mango fruit (Boag et al., 1990) by

influencing degradation of chlorophyll and formation of carotenoids on hard fruit (Vásquez-

Caicedo et al., 2005, Ornelas-Paz et al., 2008).

104

3.4.3 Firmness

γ-Irradiation did not influence ‗B74‘ fruit firmness. Citric acid and ascorbic acid (100 and 500 mM)

dipping treatments did not influence firmness either. The effects of calcium ascorbate and calcium

chloride on fruit firmness were not measured. Treatments with higher concentrations of carnauba

wax (40% – 80%) and multiple layers of 75% carnauba wax (three) delayed fruit softening (Figure

3.10 and Figure 3.11 C). Similar effects of carnauba wax in retarding firmness of ‗Kent‘ and

‗Tommy Atkins‘ mango fruit, and papaya fruit, by reducing activity of enzymes associated with cell

wall digestion such as pectin esterase (PE), polygalacturonase (PG) and cellulase have been

reported by Hoa et al. (2002). It is possible that cell wall digestion enzymes are limited by lower

internal oxygen concentrations created by the relatively impermeable wax layer (Baldwin et al.,

1999).

Enclosing ‗B74‘ fruit inside macro-perforated and paper bags for eight days did not influence

firmness (Figure 3.14 C). Exposure to elevated nitrogen atmospheres and high RH also did not

influence firmness (Figure 3.13 and Figure 3.14 C). However, polyethylene bagging for short

durations (one [24 h] or two days [48 h]) delayed firmness for the first three days but did not for the

later days (Figure 3.13). In addition, polyethylene bagging for a long duration (eight days) delayed

firmness (Figure 3.14 C) and finally caused some fruit failure to soften. Similar effects of modified

atmosphere were noted retarding ‗Fuyu‘ persimmon fruit firmness by inhibiting respiration at low

oxygen and elevated carbon dioxide levels (Ben-Arie and Zutkhi, 1992) and papaya fruit by

reducing PE, PG and cellulase activity (Lazan et al., 1992). The reason fruit failed to ripen is most

likely that mango fruit were exposed to oxygen levels below their tolerance limit which increases

anaerobic respiration and accumulates ethanol (Zagory and Kader, 1988). The responses of fruit at

different ripeness stages to modified atmosphere on firmness were different, in which polyethylene

bag treatments retarded firmness of hard fruit but not of sprung fruit. It might be associated with

different levels of enzymes (PE, PG and cellulase) activity on different ripeness stages of fruit (El-

Zoghbi, 1994).

3.4.4 Weight loss

Exposure to γ-irradiation increased weight loss from ‗B74‘ fruit. Water contributes to a high

percentage of weight in fresh fruit, and water loss thereby mostly contributes to weight loss .

Similar effects of exposure to 0.5 kGy γ-irradiation on weight loss have been reported for ‗Baladi‘

grape fruit (Al-Bachir, 1999) whereby irradiation hydrolysed water in cells to free radicals (Lester

105

and Wolfenbarger, 1990, Hayashi et al., 1992, Kovacs and Keresztes, 2002). The effects of various

chemical treatments on ‗B74‘ fruit weight loss were not clear (not measured). Coating fruit with 80%

carnauba wax, one and three layers of 75% carnauba wax resulted in lower weight loss than for

control fruit (Figure 3.11 D). Macro-perforated bagging and polyethylene bagging for eight days

also reduced weight loss (Figure 3.14 D). Increasing the RH inside macro-perforated bags and

flushing bags with a nitrogen atmosphere did not reduce weight loss (Figure 3.14 D). Modified

atmosphere created by bags and wax have been reported to reduce water loss in fruit and vegetables

(Kader et al., 1989). Treating ‗B74‘ fruit at different ripeness stages did not affect weight loss

(Figure 3.20 D).

3.4.5 TA and SSC

The effects of chemicals, bagging treatments and fruit coatings on TA and SSC were not measured.

The effects of γ-irradiation were not inconsistent on TA and SSC. In the waxing treatment, γ-

irradiation increased TA (Table 3.2), likely by influencing pH and then increasing organic acids by

(Al-Bachir, 1999, Kim and Yook, 2009). However, it did not significantly (P < 0.05) increase TA

when applied to hard, rubbery and sprung fruit.

3.5 Conclusion

Irradiating mango fruit at sprung stage instead of hard stage is an alternative method to reduce LD.

The beneficial effect of polyethylene bagging in reducing LD indicates that oxidative processes are

involved which are presumably inhibited by low oxygen. Irradiation induces oxidative stress, which

might be leading to LD. Further research into testing alterbative treatments to control these

oxidative processes is needed. The lenticel anatomy might explain the tender zones around it,

probably more susceptible to oxidative damage compared to other skin parts. Oxidative stress

theory might provide deeper insights into LD. A wider range of antioxidants from 0 to 100 mM for

postharvest treatment might be worth trying in future.

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Rojas-Graü M A, Soliva-Fortuny R, Martín-Belloso O. 2009. Edible coatings to incorporate active

ingredients to fresh-cut fruits: a review. Trends in Food Science and Technology, 20 :438–

447.

Sabato, S. F., da Silva, J. M., da Cruz, J. N., Salmieri, S., Rela, P. R. and Lacroix, M. 2009. Study

of physical–chemical and sensorial properties of irradiated ‗Tommy Atkins‘ mangoes

(Mangifera indica L.) in an international consignment. Food Control, 20: 284-288.

Sivakumar, D. and Korsten, L. 2006. Influence of modified atmosphere packaging and postharvest

treatments on quality retention of litchi cv. ‗Mauritius‘. Postharvest Biology and


Soliva‐Fortuny, R. C., Biosca‐Biosca, M., Grigelmo‐Miguel, N. and Martín‐Belloso, O. 2002.

Browning, polyphenol oxidase activity and headspace gas composition during storage of

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minimally processed pears using modified atmosphere packaging. Journal of the Science of

Food and Agriculture, 82: 1490-1496.

Thompson, A. K. 2010. In ‗Controlled Atmosphere Storage of Fruits and Vegetables (2nd

)‘. CAB

Intenational Ltd., London, UK.

Vásquez-Caicedo, A. L., Sruamsiri, P., Carle, R. and Neidhart, S. 2005. Accumulation of all-trans-

β-carotene and its 9-cis and 13-cis stereoisomers during postharvest ripening of nine Thai

mango cultivars. Journal of Agricultural and Food Chemistry, 53: 4827-4835.

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Browning and Its Prevention‘ (Lee, C. Y. and Whitaker, J. R. eds). American Chemical

Society, Washington, USA.

Zagory, D. and Kader, A. A. 1988. Modified atmosphere packaging of fresh produce. Food


111

Effects of Fruit Ripeness Stage and Polyethylene Bag Chapter 4

Packaging on Lenticel Discolouration Biochemistry after γ-Irradiation

Abstract

Lenticel discolouration (LD) is a cosmetic problem for many cultivars of mango fruit including B74.

‗B74‘ mango fruit at serial ripeness stages (hard, rubbery and sprung) were polyethylene bagged

and not. They were then subsequently exposed to either γ-irradiation or not. Thereafter, they were

kept in a ripening room at conditions of 20°C and 90 – 100% relative humidity until fully ripened.

Total phenolics concentration, polyphenol oxidase (PPO) activity and peroxidase (POD) activity

were measured towards understanding the mechanism of LD. Examination by microscopy showed

that no wax covered the lenticels, which could explain why more susceptible to oxidative damage at

/ surrounding lenticels compared to other skin parts. PPO activity at the ripeness stage of ‗hard‘ and

‗rubbery‘ was significantly (P < 0.05) higher than that of sprung for the first five days after γ-

irradiation. PPO activity was evidently related to LD induced by γ-irradiation. POD activity may

also be involved in LD as it was significantly (P < 0.05) higher in irradiated fruit. Polyethylene

bagging was associated with reduced PPO and POD activities when fruit were in their bag and at

four days later. However, LD was lower when the bag was removed, but was higher after another

four days. The total phenolics concentration was not closely related to LD. Polyethylene bagging

only reduced LD while fruit were in their bags. This transient benefit is therefore likely to be a

result of limited oxygen concentration. Overall, the effect of polyethylene bag packaging on LD

indicates that oxidative processes are involved which are presumable inhibited by low oxygen

levels. Therefore, irradiation evidently induces oxidative stress, which might lead to LD.

Keywords: Enzymes activity, ɣ-irradiation, mango fruit, postharvest treatments, phenolics

4.1 Introduction

Lenticel discolouration (LD) on mango fruit skin is evident as red, brown or black ‗halos‘

surrounding lenticels. These spots may be with or without black or brown centres (Hofman et al.,

2009). ‗B74‘ mango fruit is a particularly susceptible cultivar for LD, especially after γ-irradiation

(Joyce et al., 2011). Bezuidenhout (2005) suggested that LD might be associated with leakage of

sap from resin ducts. Alternatively, Du Plooy et al. (2009) posited that LD was a defence

mechanism involving accumulation of simple phenolics that become coagulated in cells of /

surrounding lenticel cavities.

112

Water and air entry into lenticels (Tamjinda et al., 1992), postharvest handling activities such as hot

water (Jacobi et al., 2001), disinfectants (Bally et al., 1997) and calcium hydroxide (Simão de Assis

et al., 2009) treatments, low temperature exposure (Pesis et al., 2000) and mango sap exposure

(Loveys et al., 1992) may increase LD on mango fruit.

Discolouration disorders are mostly associated with enzymatic browning in which the enzymes‘

activity (polyphenol oxidase and peroxidase), total phenolics concentration and oxygen (Franck et

al., 2007) are involved. Polyphenol oxidases (PPOs) are a family of copper-containing enzymes that

hydrolyses phenolic compounds to o-quinones that polymerize to brown melanin pigments.

Enzymes and total phenolics concentration are closely related to the browning of apple (Coseteng

and Lee, 1987) and peach fruit (Lee et al., 1990). PODs are another family of enzymes involved in

browning processes under hydrogen peroxide. In PPO-catalysed reactions, hydrogen peroxide is

generated during the oxidation of phenolic compounds (Tomás‐Barberán and Espin, 2001). POD is

also involved in the browning of litchi fruit (Jiang et al., 2004).

Modified atmosphere packaging (MAP) reduced browning of litchi fruit (Sivakumar and Korsten,

2006) and banana fruit (Nguyen et al., 2004). However, few reports of fruit ripeness stage effects

were published on fruit skin browning.

Few reports have been published on LD induced by γ-irradiation. It was hypothesised that LD

induced by γ-irradiation is enzymatic browning involving polyphenol oxidase and / or peroxidase

and total phenolics in the presence of oxygen. We contrasted different ripeness stages of fruit

experiencing γ-irradiation and also bagging at different stages of ripeness of fruit with a view to

reducing LD. Total phenolics concentration, PPO and POD activities were measured towards

understanding the mechanism of irradiation-induced LD and bagging effects.


4.2.1 Fruit materials

Hard green mature ‗B74‘ fruit (Mangifera indica L) (dry matter content Table A 1.1) were grown

under standard commercial conditions at an orchard near Childers (25°17‘S, 152°17‘E) in Southeast

Queensland, Australia and an orchard near Katherine (14°46‘S, 132°26‘E) in the Northern Territory,

Australia. Harvested fruit were de-stemmed and de-sapped in a solution of Mango Wash®

(Septone,

ITW AAMTech, NSW, Australia). They were taken to a nearby packinghouse and treated and

113



2010). Fruit were packed into single layer fibreboard trays with polyethylene liners. The fruit were

then transported to the Ecosciences Precinct (27°49‘S, 153°03‘E) in Brisbane, Queensland,

Australia or the Maroochy Research Facility in Nambour (26°62‘S, 152°95‘E), Queensland,

Australia by car and / or air-plane. They were assigned to treatments in a completely randomised

design.

4.2.2 Experiment 1. Effects of fruit ripeness stage in the 2013 – 14 season

Hard green mature ‗B74‘ fruit (dry matter content in Table A 3.1) kept in a ripening room at 20°C

and 90 – 100% RH reaching ripeness stages of hard, rubbery and sprung after 0, 3 and 8 days, were

used. The fruit were sent to the irradiation facility for exposure to γ-irradiation or not as described

in Section 4.2.4 (Section 4.2.4). Five individual fruit replicates were used in this experiment.


4.2.3 Experiment 2. Effects of bagging in the 2013 – 14 season

Different ripeness stages of (hard, rubbery and sprung) fruit from the same batch of fruit above

were polyethylene bagged or not bagged. After γ-irradiation or not as described in Section 4.2.4,

and eight days‘ storage at 20°C and 90 – 100% RH, bags were removed. Fruit were otherwise kept

in the same room until fully ripened. Five individual fruit replicates were used per treatment.


4.2.4 γ-Irradiation

The procedures were described in Section 3.3.6.

4.2.5 LD anatomy

After Parker et al. (1982) with minor modifications, 1 cm length × 0.5 cm width × 0.3 cm depth

explants of skin tissue with LD were excised with a scalpel blade. Briefly, a 0.038 mm metric

thickness feeler gauge blade was positioned as a spacer between two halved stainless steel shaver

blades. The assembly was held tightly together with a forcep (Spencer Wells, ProSciTech Pty Ltd,

QLD, Australia) and then the LD explant was cut. LD explant samples were soaked in tap water for

114

2-3 mins, followed by staining with or without 0.05% toluidine blue for 1 min. Finally, sections

were mounted on a glass slide in a drop of tap water under a glass cover slip. Hand sections were

examined at × 4, × 10 and × 20 magnifications under a light microscope (Primo Star, Carl Zeiss Pty

Ltd, Jena, Germany).

4.2.6 Biochemical assays

Skin tissues were removed with a fruit peeler, wrapped in aluminum foil, dip frozen in liquid

nitrogen for 30 s, and stored for later analysis at – 80°C freezer (Ultima II – 80, Thermo Electron

Corporation, MA, USA). The skin tissue collected from 1 – 2 fruit was taken as the replicate and

three replicates were collected. PPO and POD activities were assayed with modification after Cao et

al. (2010). Frozen mango peel was ground in liquid nitrogen to a fine powder in a grinding jar

(tissue lyser II, Qiagen, Heidelberg, Germany) using tissue lyser (tissue lyser II, Qiagen, Heidelberg,

Germany). Then about 0.1 g of the fine powder was added into 1 ml of pre-cooled 0.5 M, pH - 6.5

phosphate buffer (Sigma-Aldrich Inc., MO, USA) containing 5% (w / v) polyvinyl pyrrolidone – 40

(Sigma-Aldrich Inc., MO, USA). The homogenate was mixed thoroughly with a vortex mixer

(Chiltern MT 19, Selby Scientific and Medical, WA, Australia) and then centrifuged at 14,000 x g

for 20 min at 4°C (Microfuge®

22R, Beckman Coulter Inc., Brea California, USA). The supernatant

was used to assay the activity of PPO and POD enzymes.

For PPO activity, the 1.2 ml reaction mixture contained 0.6 ml of 0.05 M, pH - 6.5 phosphate buffer,

0.3 ml crude enzyme extract and 0.3 ml of 0.3 M catechol (Sigma-Aldrich Inc., MO, USA). One

unit of activity was defined as an increase in absorbance at 420 nm of 0.01 min-1

with a

spectrophotometer (Du 800, Beckman Coulter Inc., Brea California, USA) and PPO activity was

expressed as units / mg Protein.

For POD activity, the 1.21 ml reaction mixture contained 0.6 ml of 0.05 M, PH - 6.5 phosphate

buffer, 0.3 ml crude enzyme extract, 0.3 ml of 0.3% (v / v) guaiacol (Sigma-Aldrich Inc., MO, USA)

and 0.01 ml of 0.4% H2O2 (Chem-supply Inc., SA, Australia). One unit was defined as an increase

in absorbance at 470 nm of 0.01 min-1

with a spectrophotometer and POD activity was expressed as

units / mg Protein.

Total protein concentration was tested by Bio-rad assay using bovine serum albumin (Bio-Rad

Laboratories Inc., California, USA) as a standard. Protein concentration was calculated using a

standard curve and expressed as mg of bovine serum albumin per g of frozen sample.

115

To determine the total phenolics concentration, the ground sample was weighed about 0.1 g and

added to 1 ml of 1% HCl-ethanol (Sigma-Aldrich Inc., MO, USA) and stirred absolutely for 2 h at

4oC and then centrifuged for 20 min at 14,000 x g at the same temperature. The supernatant was

diluted with Millipore water for 20-fold and vortex mixed completely. The 1 ml reaction mixture

contained 0.05 ml diluted supernatant, 0.1 ml Folin-Ciocalteu reagent (Sigma-Aldrich Inc., MO,

USA) and 0.85 ml sodium carbonate (Chem-Supply Inc., Port Adelaide SA, Australia). The

solution absorbance at 765 nm was measured with a spectrophotometer. Absorbances were used to

calculate total phenolics concentration against gallic acid (Sigma-Aldrich Inc., MO, USA) as

standards. Total phenolics concentration was calculated using a standard curve and expressed as mg

of gallic acid (GA) (phenol equivalent) per g of frozen samples.

4.2.7 Experimental design and statistical analyses

Completely randomized designs were used in all experiments. Total phenolics concentration, PPO

and POD activities were analysed in GenStat (2013) using general ANOVA by different factors for

different experiments. The factors in experiment 1 are in terms of time (days 1, 3, 5, 8 and 12),

irradiation (non-irradiation and irradiation) and fruit ripeness stage (hard, rubbery and sprung). The

factors in experiment 2 are in terms of time (days 8 and 12), irradiation (non-irradiation and

irradiation), fruit ripeness stage (hard, rubbery and sprung) and bagging (no bagging and bagging).

Three replicate sets per treatment, with each set collected from 1 – 2 fruit, were used in these

experiments. The significance of differences between treatments means was tested with the

protected Fisher‘s test at the 5% level.

4.3 Results

4.3.1 LD anatomy

Lenticels on ‗B74‘ mango fruit were found not to be covered by a cuticle wax layer, potentially

leaving an open pathway for oxygen entry into the fruit (Figure 4.1 A, B and C). LD involved

severe coloured browning of cells lining the lenticel and of surrounding cells (Figure 4.1 A, B and

C) as compared to healthy lenticels (Figure 4.1 D). No differences in LD were observed between

stained or non-stained lenticels.

116

Figure 4.1 Transverse unstained hand sections of LD through irradiated and ripened ‗B74‘ mango

fruit skin samples (A): [× 4], (B): [× 10], (C) [× 20] and D [× 20]. Scale bars in A, B, C and D

represent 100 µm, 50 µm, 20 µm and 20 µm respectively. RD: resin duct. L: lenticel cavity.

4.3.2 Experiment 1. Effects of fruit ripeness stage in the 2013 – 14 season

When fruit at different ripeness stages all reached to eating ripe, a significant (P = 0.034)

interaction of irradiation and fruit ripeness stage was found for total phenolics concentration (Table

4.1). Sprung fruit subjected to irradiation had significantly (P < 0.05) lower total phenolics

concentration than did hard fruit with irradiation.

A B

C D

117

Irradiation and fruit ripeness stage were all found significantly (P < 0.05) different with regard to

PPO and POD activities (Table 4.2). Irradiated fruit had significantly (P < 0.001; P < 0.001) higher

PPO and POD activities than non-irradiated fruit. Rubbery fruit had significantly (P < 0.05) higher

PPO activity than did hard fruit. However, sprung fruit had significantly (P < 0.05) higher POD

activity than did hard fruit.

Table 4.1 A significant (P = 0.034) interaction of fruit ripeness stage and irradiation for total

phenolics concentration (mg GA equivalents / g FW) in skin tissue at eating ripe (n = 3). ‗B74‘ fruit

from Southeast Queensland in the 2012 – 13 season reached hard, rubbery and sprung after 0, 3 and

8 days in a ripening room at 20°C and 90 – 100% RH. The fruit were exposed to either 0 or 576 Gy

(min – max: 493 – 716 Gy) γ-irradiation and finally kept in the ripening room at 20°C and 90 –

100% RH until fruit reached eating ripe. Data are expressed as mean and those followed by the

same letters are not significant.

Factors Total phenolics concentration

Irradiation × fruit ripeness stage

Hard, no irradiation 18.61 ab

Rubbery, no irradiation 22.70 b

Sprung, no irradiation 20.71 b

Hard, irradiation 21.92 b

Rubbery, irradiation 19.53 ab

Sprung, irradiation 16.34 a

Factorial ANOVA

Irradiation NS

Fruit ripeness stage NS

Irradiation × fruit ripeness stage *

NS: not statistically significant. *: statistically significant (P < 0.05)

118

During ripening, a significant (P < 0.001) interaction of time and fruit ripeness stage was found for

total phenolics concentration (Figure 4.2 A). Total phenolics concentration crossed over from day 1

to 12. Total phenolics concentration increased in hard and rubbery fruit from day 5 and 3,

respectively. However, the total phenolics concentration increased in sprung fruit from day 1. A

significant (P < 0.001) interaction of time and irradiation was found for POD activity (Figure 4.2 B).

Irradiated fruit increased in POD activity higher than did non-irradiated fruit. Irradiated fruit had

significantly (P < 0.05) higher POD activity than did non-irradiated fruit on day 12. A significant (P

< 0.001) interaction of time, irradiation and fruit ripeness stage was found for PPO activity (Figure

4.2 C). Irradiated hard and rubbery fruit increased in PPO activity to higher levels on day 5 than for

the non-irradiated ones, and then all decreased after that. However, PPO activity of irradiated

sprung fruit decreased firstly and then increased.

Table 4.2 Significant effects of irradiation (n = 9) and fruit ripeness stage (n = 6) on PPO and POD

activities (units / mg Protein) in skin tissue at eating ripe. ‗B74‘ fruit from Southeast Queensland in

the 2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at

20°C and 90 – 100% RH. The fruit at different ripeness stages exposed to either 0 or 576 Gy (min –

max: 493 – 716 Gy) and kept in the ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe. More details seen in Table A 2.1.

Factors POD activity PPO activity

Irradiation

No irradiation 25.8 a 25.4 a

Irradiation 47.9 b 56.2 b

Fruit ripeness stage

Hard 42.38 b 47.0 b

Rubbery 39.08 b 32.9 a

Sprung 29.17 a 42.5 ab

Factorial ANOVA

Irradiation *** ***

Fruit ripeness stage * *

Irradiation × fruit ripeness

stage

NS NS



119

Figure 4.2 A: A significant (P < 0.001) interaction of fruit ripeness stage and time for total

phenolics concentration (mg GA / g FW) in skin tissue (n = 6). B: A significant (P < 0.001)

interaction of irradiation and time for POD activity (units / mg Protein) in skin tissue (n = 9); C: A

significant (P < 0.001) interaction of fruit ripeness stage, irradiation and time for PPO activity (units

/ mg Protein) in skin tissue (n = 3). ‗B74‘ fruit from Southeast Queensland in the 2013 – 14 season

reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100%

RH. The fruit were exposed to either 0 or 576 Gy (min – max: 493 – 716 Gy) γ-irradiation and

finally kept in the ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. More

C

TP

co

ncen

trat

ion (

mg G

A /

g F

W)

0

5

10

15

20

25

Hard

Rubbery

Sprung

LSD

PO

D a

ctivity (

units

/ m

g P

rote

in)

0

20

40

60

80

No irradiation

Irradiation

LSD

Time from irradiation (days)

0 2 4 6 8 10 12

PP

O a

ctivity (

units

/ m

g P

rote

in)

0

50

100

150

200




Hard, irradiation


Sprung, irradiation

LSD

A

B

120

4.3.3 Experiment 2. Effects of bagging in the 2013 – 14 season

A significant (P = 0.024) interaction of irradiation, fruit ripeness stage, bagging and time was found

for total phenolics concentration (Table A 2.5). Fruit subjected to treatments developed in total

phenolics concentration with different trends across sequential times (Figure 4.3). Non-irradiated

hard control fruit had significantly (P < 0.05) higher total phenolics concentration than did

irradiated hard control fruit on day 8. However, significantly (P < 0.05) higher total phenolics

concentration was found in non-irradiated rubbery control fruit than in irradiated rubbery fruit on

day 8. On day 8, non-irradiated hard and sprung fruit enclosed in polyethylene bags had

significantly (P < 0.05) higher total phenolics concentration than did irradiated hard and sprung fruit

enclosed in polyethylene bags. However, non-irradiated rubbery fruit enclosed in polyethylene bags

had significantly (P < 0.05) lower total phenolics concentration than did irradiated hard and sprung

fruit enclosed in polyethylene bags on day 8. On day 12, the irradiated rubbery fruit enclosed in

polyethylene bags exhibited decreased total phenolics concentration, but irradiated hard and sprung

enclosed in polyethylene bags exhibited increased total phenolics concentration.

Figure 4.3 A significant (P = 0.024) interaction of time, fruit ripeness stage, bagging and irradiation

for total phenolics concentration (mg GA equivalents / g FW) in skin tissue (n = 3). ‗B74‘ fruit from

Southeast Queensland in the 2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8

days in a ripening room at 20°C and 90 – 100% RH. The fruit were treated with polyethylene bags

with or without nitrogen. The fruit not held in bags were the controls. They were subsequently


8 12

Tota

l phen

oli

cs c

once

ntr

atio

ns

(mg G

A /

g F

W)

0

5

10

15

20

25Hard, no bagging (control), no irradiation Rubbery, no bagging (control), no irradiation Sprung, no bagging (control), no irradiation Hard, bagging, no irradiation Rubbery, bagging, no irradiation Sprung, bagging, no irradiation Hard, no bagging (control), irradiation Rubbery, no bagging (control), irradiation Sprung, no bagging (control), irradiation Hard, bagging, irradiation Rubbery, bagging, irradiation Sprung, bagging, irradiation

LSD = 3.90

details seen in Table A 2.2, Table A 2.3 and Table A 2.3.

121

exposed to either -irradiation or not and finally kept in the ripening room at 20°C and 90 – 100%

RH until fruit reached eating ripe. More details seen in Table A 2.5.

A significant (P = 0.043) interaction of irradiation and time was found for POD activity (Figure 4.4

A). Irradiation increased in POD activity higher than non-irradiation from day 8 to 12 (Figure 4.4

A). Irradiated fruit had similar POD activity as non-irradiated fruit on day 8, but significantly (P <

0.05) higher POD activity than did non-irradiated fruit on day 12 (Figure 4.4 A). A significant (P =

0.016) interaction of irradiation, bagging and ripeness was found for POD activity (Figure 4.4 B).

Irradiation increased POD activity for control fruit at three ripeness stages but not for fruit at three

ripeness stages that were enclosed with polyethylene bags. Irradiated fruit at different ripeness

stages enclosed with polyethylene bags had significantly (P < 0.05) lower POD activity compared

to non-irradiated control fruit at different ripeness.

Figure 4.4 A: A significant (P = 0.043) interaction of time and irradiation for POD activity (units /

mg protein) (n = 18). B: A significant (P = 0.016) interaction of irradiation, fruit ripeness stage and

bagging for POD activity (units / mg protein) in skin tissue (n = 6). ‗B74‘ fruit from Southeast

Queensland in the 2013 – 14 season reached hard, rubbery and sprung after 0, 3 and 8 days in a

ripening room at 20°C and 90 – 100% RH. The fruit were treated with polyethylene bags with or

without nitrogen. The fruit not held in bags were the controls. They were subsequently exposed to

LSD = 6.59

Treatment

No irradiation Irradiation

PO

D a

ctvit

y (

unit

s /

mg P

rote

in)

0

20

40

60

80

Hard, no bagging

Rubbery, no bagging

Sprung, no bagging

Hard, bagging

Rubbery, bagging

Sprung, bagging

LSD　= 6.70


8 12

PO

D a

ctiv

ity

(unit

s /

mg P

rote

in)

0

20

40

60

80

No irradiation

Irradiation

A B

122

either -irradiation or not and finally kept in the ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe. More details seen in Table A 2.7.

A significant (P < 0.001) interaction of ripeness, bagging and time was found for PPO activity

(Figure 4.5 A). PPO activity of different ripeness stages of fruit changed with different trends across

different times. Different ripeness stages of fruit enclosed in polyethylene bags had significantly (P

< 0.05) lower PPO activity than different ripeness stages of control fruit on day 12 but not day 8.

Another three significant (P < 0.001, P < 0.001; P = 0.007) interactions associated with irradiation

were found for PPO activity (Figure 4.5 B, C, D). Irradiation produced significantly (P < 0.05)

higher PPO activity in fruit than did non-irradiation.

123

Figure 4.5 A: A significant (P < 0.001) interaction of time, fruit ripeness stage and bagging for PPO

activity (n = 6); B: A significant (P = 0.007) interaction of irradiation and fruit ripeness stage for

PPO activity (n = 12); C: A significant (P < 0.001) interaction of irradiation and time for PPO

activity (n = 18); D: A significant (P < 0.001) interaction of irradiation and bagging for PPO

activity (n = 12). ‗B74‘ fruit from Southeast Queensland in the 2013 – 14 season reached hard,

rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH. The fruit

were treated with polyethylene bags with or without nitrogen. The fruit not held in bags were the

controls. They were subsequently exposed to -irradiation or not, and finally kept in the ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. More details seen in Table A 2.6.

LSD = 7.33

A B

C D

A B, C and D


6 8 10 12 14

PP

O a

ctiv

ity (

un

its

/ m

g P

rote

in)

0

20

40

60

80

Hard, no baggingRubbery, no bagging Sprung, no bagging Hard, bagging Rubbery, bagging Sprung, bagging

LSD　= 6.70


6 8 10 12 14

PP

O a

ctiv

ity （

un

its

/ m

g P

rote

in)

0

20

40

60

80

No irradiation Irradiation

LSD = 5.98

Fruit ripeness

Hard Rubbery Sprung

PP

O a

ctiv

ity (

un

its

/ m

g P

rote

in)

0

20

40

60

80

Treatments

No bagging Bagging

PP

O a

ctiv

ity (

un

its

/ m

g P

rote

in)

0

20

40

60

80LSD = 7.33

124

4.4 Discussion

Fruit at different ripeness stages that were not bagged all ripened successfully in terms of reaching

eating firmness. At eating ripe stage, sprung fruit with ɣ- irradiation had significantly (P < 0.05)

lower LD than did hard and rubbery fruit exposed to ɣ- irradiation (Fig. A.1). Sprung fruit with ɣ-

irradiation had significantly (P < 0.05) lower total phenolics concentration than hard fruit with ɣ-

irradiation (Table 4.1). The LD on fruit treated with irradiation significantly (P < 0.05) increased on

the day of irradiation. However, there were no significant (P = 0.05) differences in total phenolics

concentration between irradiated and non-irradiated mango fruit after the day of irradiation.

Therefore, the total phenolics concentration is apparently not closely related to LD induced by ɣ-

irradiation. The PPO activity in hard and rubbery fruit exposed to irradiation increased from day 1

to a transient peak on day 5. However, sprung fruit with irradiation decreased slightly in PPO

activity from day 1 down to a minimum on day 5 and subsequently increased. This difference in

trends could explain why LD of sprung fruit increased less than it did in hard and rubbery fruit in

the first 5 days in Chapter 3. Similar effects of γ-irradiation of increased PPO activity have been

reported in relation to browning of bananas (Thomas and Nair, 1971) and of mushroom (Benoit et

al., 2000). Irradiation had higher POD activity on days 8 and 12, which was consistent with higher

LD on irradiated fruit than on non-irradiated fruit. Therefore, increased POD activity, as induced by

γ-irradiation, might be involved in LD. Higher POD activity have been reported in irradiated sweet

potato discs as compared to non-irradiated sweet potato discs (Ogawa and Uritani, 1970). It is

interesting to find that similar PPO activity at any time was found in irradiated and non-irradiated

sprung fruit which showed significantly different levels of LD. It might be that the effects of

irradiation on the cell membrane and integrity is possible involved (Kovacs and Keresztes, 2002),

which needs studied further.

Irradiated fruit enclosed in polyethylene bags was found significantly (P < 0.05) lower LD on days

8 and 12 as compared with irradiated control fruit, although LD increased after day 8 upon

(removing the bags). The changes in total phenolics concentration were not consistent with the

increases in LD across different days. Bagging reduced PPO activity on days 8 and 12, although the

differences on day 8 were not significant (P = 0.05). Bags were found to reduce PPO activity in

fresh-cut lotus (Xing et al., 2010) and in regard to banana browning (Nguyen et al., 2004). However,

PPO activity trends were not consistent with LD development as was the case for bagging and POD

activity. By contrast, MAP was associated with reduced POD activity at three developmental stages

of pear fruit (Zhang et al., 2007). In the present study, however, bagging was associated with

125

significantly (P < 0.05) reduced POD activity in irradiated fruit, which was seemingly inconsistent

with the absence of significant (P < 0.05) differences in LD between the bagged and non-bagged

fruit on days 12. PPO and POD enzyme activities, and total phenolics concentration were

apparently not the main reason linked to the observed bagging effects on reducing LD.

Consequently, the lower concentration of oxygen in the sealed bags is the likely reason that bagging

reduced LD. This proposition is supported by the observation that LD increased after the bags were

removed, allowing the irradiated fruit to ripen in ambient air. A similar outcome was reported for

banana peel spotting in association with oxygen concentration (Choehom et al., 2004).

4.5 Conclusion

The effect of polyethylene bag packaging on LD indicates that oxidative processes are involved

which are presumable inhibited by low oxygen. γ-Irradiation induces oxidative stress, which leads

to LD in association with increased PPO activity, and POD activity might also be involved.

Examination by microscopy showed that no wax covered the lenticels. This could explain why

lenticels are more susceptible to oxidative damage as compared to other skin parts. Total phenolics

concentration was shown not to be related to be lenticel discolouration induced by γ-irradiation in

this experiment. However, measurements were not made on lenticel tissues per se versus rest of the

skin tissue. Another possible reason for the effects of γ-irradiation is that disruption of cell

membrane and integrity is involved. Therefore, better understanding of LD anatomy and

physiology under transmission electronic microscopy (TEM) is warranted in future.

References

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641-647.

126

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Jacobi, K., MacRae, E. and Hetherington, S. 2001. Effect of fruit maturity on the response of

‘Kensington‘ mango fruit to heat treatment. Animal Production Science, 41: 793-803.

Jiang, Y., Duan, X., Joyce, D., Zhang, Z. and Li, J. 2004. Advances in understanding of enzymatic

browning in harvested litchi fruit. Food Chemistry, 88: 443-446.


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phenolic compounds and polyphenoloxidase activity among various peach cultivars. Journal

of Agricultural and Food Chemistry, 38: 99-101.





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plant tissues. The American Biology Teacher, 487-489.






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their discolouration in mangoes (Mangifera indica cv. ‗Namdokmai‘). Kasetsart Journal, 26:

57-64.

Thomas, P. and Nair, P. 1971. Effect of gamma irradiation on polyphenol oxidase activity and its

relation to skin browning in bananas. Phytochemistry, 10: 771-777.

Tomás‐Barberán, F. A. and Espin, J. C. 2001. Phenolic compounds and related enzymes as

determinants of quality in fruits and vegetables. Journal of the Science of Food and


Xing, Y., Li, X., Xu, Q., Jiang, Y., Yun, J. and Li, W. 2010. Effects of chitosan-based coating and

modified atmosphere packaging (MAP) on browning and shelf life of fresh-cut lotus root

(Nelumbo nucifera Gaerth). Innovative Food Science and Emerging Technologies, 11: 684-

689.

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Sinica, 34: 565-568.

128

Effect of Storage Temperature on Under-skin Browning on Chapter 5

‘Honey Gold’ Mango Fruit

Abstract

Under-skin browning (USB) on ‗Honey Gold‘ mango fruit is a disorder that occurs in sub-

epidermal cells. Six experiments were conducted with a view to understanding the influence of

postharvest storage temperature on USB. The experiments examined the effects of fruit size, storage

temperature, delayed cooling or abrasion, fruit growing region, abrasion and intact fruit versus skin

discs on USB development. Fruit was sourced from the Northern Territory, north Queensland and

Southeast Queensland. The incidence and severity of USB were measured in all experiments. Other

parameters, such as chlorophyll fluorescence (Fv / Fm), skin colour, firmness and weight loss, were

also measured. Fruit size did not consistently influence USB incidence and severity. Delayed

abrasion of fruit from North Queensland did not influence USB incidence and severity. Delayed

fruit from North Queensland cooled did not influence the incidence of USB. However, delayed fruit

from North Queensland cooling on day 4 decreased the severity of USB as compared to delayed

fruit from North Queensland cooling on day 0. However, storage duration at 13°C was related to the

severity of USB. Increasing storage duration at the low temperature of 13°C evidently resulted in

incrementally greater severity of USB on abraded fruit from the Northern Territory. The fruit

growing region was directly related to the susceptibility to developing USB. Fruit produced in

hotter tropical climate of the Northern Territory were more susceptible to developing USB than

were fruit grown in cooler tropical climate of North Queensland and in the relatively cooler sub-

tropical climate of Southeast Queensland. Abrasion evidently induced USB and low temperature

intensified USB incidence. Low storage temperatures of ≤ 12°C delayed skin colour change from

green to yellow, delayed fruit softening, and reduced weight loss for fruit from all three regions.

There were similar levels of Fv / Fm in the intact fruit skin or excised skin discs exposed to different

temperatures. Taken overall, USB is not simply a chilling injury per se, but is possibly induced by

physical stress (e.g. abrasion) and intensified by exposure to low temperature.

Keywords: abrasion test, fruit growing region, low storage temperature, mango fruit, quality

parameter, USB

129

5.1 Introduction

‗Honey Gold‘ mango is an Australian cultivar bred from ‗Kensington Pride‘ and an unknown

cultivar in 2002 ( G. Scurr, pers. comm., 2013). It currently contributes 4% of the total mango

production in Australia (AMIA, 2014). ‗Honey Gold‘ is popular with consumers because of its

appealing yellow-orange skin, fibreless flesh and good taste. About 140,000 trees are presently

under cultivation on 500 hectares in the Northern Territory, Queensland, New South Wales,

Victoria and Western Australia (Pinata, 2015). The fruit harvest season typically begins in

November in the Northern production areas and ends in March in the Southern districts.

Under-skin browning (USB) is a physiological disorder that affects ‗Honey Gold‘ fruit. It is

manifested as a brown-grey bruise-like lesion in the sub-epidermal cells of fruit. Starch accumulates

in ‗Honey Gold‘ fruit affected by USB (Marques, 2012). This disorder is typically expressed in

ripening fruit after long distance transportation from farms in the Northern Territory and North

Queensland to metropolitan markets in the southern states of Australia (Hofman et al., 2009).

Hofman et al. (2009) suggested that postharvest abrasion of the fruit skin with sandpaper could be

used as a tool for inducing USB symptoms.

Chilling injury (CI) on fruit is often manifested as skin browning after a critical period of exposure

to non-freezing temperatures below 10 – 15°C (Wang, 1993). CI generally appears rapidly after

produce is removed from chilling to ambient temperature (Paull, 1990). Membrane damage is

among the mechanistic causes of chilling injury (Lyons, 1973). Mango fruit are generally

susceptible to chilling injury when stored below 12 – 13°C (Gonzalez-Aguilar et al., 2000). Some

mango cultivars are inherently more susceptible than others to chilling injury (Phakawatmongkol et

al., 2004).

Chlorophyll fluorescence has been widely used as a tool to detect chilling of fruit before severe

visual damage is evident (Smillie and Hetherington, 1983, Bolhar-Nordenkampf et al., 1989). The

Fv / Fm parameter measured in the dark < 0.7 indicates membrane damage by chilling injury.

In the present study, the working hypothesis, that USB is a symptomatic form of chilling injury that

develops as a result of exposure to low temperature and physical damage, was tested. Six

experiments were completed with a view to identifying the role of chilling temperatures in USB

expression on ‗Honey Gold‘ fruit. The experiments evaluated the response of fruit and skin discs

from different production regions to different storage temperatures and durations, delayed cooling

130

and abrasion via the abrasion test developed by Hofman et al. (2009). The experiments were

conducted in the 2011 – 12, 2012 – 13 and 2013-14 seasons. The incidence and severity of USB

were measured in all experiments. Chlorophyll fluorescence (Fv / Fm) was measured in experiments

5 and 6. Other parameters such as skin colour, firmness and weight loss were measured in

experiment 5.


5.2.1 Materials

Green mature ‗Honey Gold‘ mango fruit were commercially harvested from a farm near Fox Road

in Katherine, Northern Territory, Australia (14°27‘S, 132°15‘E) in November, from a farm near

Mutchilba in North Queensland, Australia (17°8‘S, 145°12‘E) in early January, and from a farm

near Wamurran in Southeast Queensland, Australia (27°2‘S, 152°51‘E) in late January or early

February during the 2011 – 12, 2012 – 13 and 2013 – 14 seasons. They were taken to a nearby

packinghouse and treated and packed under standard commercial conditions, including fungicide

treatment (Sportak®, a.i. prochloraz, Bayer Crop Science, VIC, Australia), brushing, drying and

sorting (Hofman et al., 2010). Two layers of plastic bubble wrap were placed on top of fruit in each

fibre tray to reduce physical stress during transport. Fruit grown in the Northern Territory and North

Queensland were air-freighted to Brisbane airport within 24 – 36 h. They were then transported by

car to the postharvest laboratory at the Ecosciences Precinct in Brisbane or to the Maroochy

Research Facility in Nambour, Queensland, Australia within 1 – 2 h. Fruit grown in Southeast

Queensland were transported by car to the Ecosciences Precinct or the Maroochy Research Facility

described above within 1 – 2 h. Upon arrival in the laboratory, all fruit were randomly assigned to

treatments.

5.2.2 Abrasion test

An abrasion test was conducted using sandpaper following the method of Hofman et al (2009) in

experiments 1, 2, 3 and 4. The abrasion test was also used with a minor modification in experiments

5 and 6. A single sheet of sandpaper (120 grits, Trojan, NSW, Australia) was fitted to an ‗Ozito‘

detail sander (280 W, Ozito Industries Pty Ltd, VIC, Australia). For the test treatment, an individual

mango fruit was placed on a sealed sand bag on an adjustable laboratory scissor jack and abraded at

four positions for 2 s each (Figure 5.1). The resultant abrasion area was about 0.8 – 2 cm2.

131

5.2.3 Experiment 1. Effects of storage temperature and fruit size on abraded fruit in the 2011

– 12 season

The purpose of this experiment was to determine the effects of storage temperature and fruit size on

USB expression for abraded fruit. Fruit were harvested from the Northern Territory as described in

Section 5.2.1 during the 2011 – 12 season. After complete randomisation, fruit were abraded as

described in Section 5.2.2. Fruit of different sizes; small (16 / tray), medium (14 / tray) and large

(12 / tray) were kept in cold rooms operating at 7 or 10 or 13 or 16 or 20°C, and 90 – 100% RH for

6 days. The fruit were then maintained in a ripening room at 20°C and 90 – 100% RH until fruit

reached eating ripe. Twelve, 14 and 16 individual fruit replicates were used for fruit of large,

medium and small sizes, respectively, in this experiment. Individual fruit was taken as the replicate.

5.2.4 Experiment 2. Effects of storage duration and fruit size on abraded fruit in the 2011 – 12

season

The objective of this experiment was to determine the effects of storage duration and fruit size on

USB expression for abraded fruit. Additional fruit from the same sample batch used in Section 5.2.3

were used. After abrasion (Section 5.2.2), fruit of different sizes; small (16 / tray), medium (14 /

tray) and large (12 / tray) were kept in a cold room at 13°C and 90 – 100% RH for 1 or 3 or 6 or 9

days. All fruit were then kept in a ripening room until they reached eating ripe. Twelve, 14 and 16

individual fruit replicates were used for fruit of large, medium and small size, respectively, in this

experiment. Individual fruit was taken as the replicate.

Figure 5.1 Image of the assembly for mango fruit abrasion test application

132

5.2.5 Experiment 3. Effects of delayed cooling on abraded fruit in the 2011 – 12 season

The purpose of this experiment was to determine the effect of delayed cooling on USB expression

for abraded fruit. Fruit were harvested from North Queensland as described in Section 5.2.1 during

the 2011 – 12 season. After abrasion (Section 5.2.2), the fruit were kept in a ripening room at 20°C

and 90 – 100% RH. Fruit were then transferred to a cold room at 13°C and 90 – 100% RH on day 0

or 1 or 2 or 4. The fruit were maintained at 13C for an additional six days. Thereafter, the fruit

were held in a ripening room until they reached eating ripe as described above. Additional abraded

fruit, as the controls, were continuously maintained at 20ºC and 90 – 100% RH until they reached

eating ripe. Five individual fruit replicates were used in this experiment. Individual fruit was taken

as the replicate.

5.2.6 Experiment 4. Effects of delayed abrasion test on abraded fruit in the 2011 – 12 season

This experiment was designed to determine the effect of delayed abrasion on USB expression for

abraded fruit. Additional fruit from the same sample batch used in Section 5.2.5 were used. After

harvest, the fruit were kept in a cold room operating at 13ºC and 90 – 100% RH, and then abraded

on day 0 or 1 or 2 or 4 or 6. After abrasion (Section 5.2.2), the fruit were maintained at 13C for an

additional six days. Fruit were then held in a ripening room until they reached eating ripe as

described above. Additional fruit that were not abraded and maintained in a cold room at 13°C or

20°C, and 90 – 100% RH for six days and subsequently kept in a ripening room at 20°C and 90 –

100% RH were the controls. Five individual fruit replicates were used in this experiment. Individual

fruit was taken as the replicate.

5.2.7 Experiment 5. Effects of storage temperature, fruit growing region and abrasion test on

fruit in the 2012 – 13 season

The objective of this experiment was to determine the effects of fruit growing region, storage

temperature and abrasion test on USB expression and chlorophyll fluorescence (Fv / Fm) for the

intact fruit. Green mature ‗Honey Gold‘ mango fruit grown in the Northern Territory, North

Queensland and Southeast Queensland were harvested during the 2012 – 13 season as per the

procedures described in Section 5.2.1. The fruit were abraded or not abraded. All fruit were then

kept in rooms at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH for eight days. Fruit were finally

kept in ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Fifteen individual

fruit replicates were used in this experiment.

133


season

The purpose of this experiment was to determine the effects of temperature on USB expression and

chlorophyll fluorescence (Fv / Fm).on excised skin discs. Fruit harvested from the Northern Territory

and North Queensland were from the same batch sample used in Section 5.3.7. The wells in the

temperature gradient block (Figure 5.2) were partly filled with distilled water. A 10 cm diameter

filter paper was then placed flat over the openings of each well to contact to the distilled water and

covered by the polystyrene. Before commencing treatments, the temperature gradient block was

operated for at least 1 day to equilibrate to treatment temperatures. A 1 cm diameter cork borer was

then used to collect cylinders of mango skin plus flesh. The flesh was trimmed away from the skin

to leave a 3 mm thickness. These skin discs were then placed onto filter paper through the holes of

the polystyrene cover in a vertical line using tweezers. The chlorophyll fluorescence parameter Fv /

Fm was assessed at different times when it was dark. All the skin discs were collected from 15

individual fruit and pooled together. Three skin disc replicates per treatment were used for this

experiment and the individual skin disc was taken as the replicate.

Figure 5.2 Image of thermal gradient block set up with associated apparatus including water bath

unit (A), cooling unit (B), and the temperature gradient block with holes (C).

A B

C

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5.2.9 Measurements

5.2.9.1 USB severity (rating scale) and incidence

Individual fruit were visually rated for the severity of USB at different times during treatment and

ripening. The rating scale used was: 0 = no USB symptoms; 1 = < 3% (1 cm2) of skin surface

affected; 2 = ~ 3% (1 – 3 cm2); 3 = ~ 10% (3 – 12 cm

2); 4 = 10% – 25%; and 5 = > 25% of skin

surface affected (Holmes et al., 2010). Fruit affected by USB that directly surrounded any of the

four abraded positions was considered to be abrasion-related USB (AUSB). Fruit affected by USB

that occurred at a position away from the abrasion zone was considered extra USB (EUSB). When

the AUSB and EUSB were combined on a single fruit, it was termed total USB (TUSB). The

incidence of AUSB, EUSB and TUSB was calculated by dividing the number of fruit affected with

the respective symptoms by the total number of replicates used in experiments.

5.2.9.2 USB severity (area)

The USB area was calculated by linear measurements as described below.

The length (L) and the width (W) of each abraded area were measured with a ruler and of each

affected USB area was calculated using the following formula based on ellipse area

(https://en.wikipedia.org/wiki/Ellipse).

AreaAUSB = Π × (LUSB / 2) × (WUSB / 2) – Π × (LAbrasion / 2) × (WAbrasion / 2).

AreaEUSB = Π × (LEUSB / 2) × (WEUSB / 2)

AreaTUSB = AreaAUSB + AreaEUSB

USB area was calculated using Image J analysis software (National Institute of Mental Health,

Bethesda, Maryland, United States; http://imagej.nih.gov/ij/)

A graduated ruler was placed beside fruit showing USB symptoms. Photographs of fruit skin

affected with USB together with the ruler were taken with a camera (IXUS130, Canon Inc., Tokyo,

Japan) using a macro setting. The images were saved in ‗JPEG‘ format. The area of USB and the

abrasion area were calculated with Image J (Image Processing and Analysis in Java) software. The

following protocol was followed: 1. Open the photo: select ‗file – open‘; 2. Set the scale according

135

to the ruler: select ‗arrow‘ and draw a length of 1 cm according to the ruler in the image, select

‗Analyze‘ – ‗set scale‘ and then ‗known distance‘ as 1; 3. Calculate the area: ‗polygon selections‘,

draw (trace) the edge of the abrasion or USB lesion and select ‗Analyze – measure‘. The following

affected area calculations were made:

AreaAUSB = AreaAUSB+Abrasion – AreaAbrasion

AreaEUSB = AreaEUSB

AreaTUSB = AreaAUSB + AreaEUSB

The area of USB surrounding the position of abrasion (AUSB) for each fruit was the sum of the

AUSB caused by the four abrasions. The area of EUSB for each fruit was the sum of EUSB

occurring in the intact fruit. The area of TUSB for each fruit was the AUSB area plus the EUSB

area.

5.2.9.3 Chlorophyll fluorescence

The chlorophyll fluorescence induction parameters of mango fruit peel were determined in cold

rooms with different temperatures using a pulse amplitude modulated fluorometer (OS-30P, Opti-

science Inc., NH, USA). The fruit were dark-adapted for 30 min inside cold rooms before the

measurements were captured.

5.2.9.4 Quality parameters

Fruit skin colour, firmness and weight loss were determined using the same procedures described in

Section 3.3.2.3.


A completely randomised design was used in all experiments. All data were analysed using GenStat

(2013). The incidence of AUSB, EUSB and TUSB was used to do statistical analyses using a

generalized linear model (McCullagh and Nelder, 1989) with binomial distribution and logistic

regression by different treatment factors for different experiments. Conditional unbalanced

ANOVA with log transformation (MacNeil et al., 2009) was used to analyse on the severity (area)

of TUSB, AUSB and EUSB by different factors for different experiments.

136

The factors for AUSB, EUSB and TUSB incidence and severity analyses in experiment 1 were fruit

size (large, medium and small) and temperature (20, 16, 13, 10 and 7°C). The factors in experiment

2 were fruit size (large, medium and small) and duration (1, 3, 6 and 9 days). The factor in for

AUSB, EUSB and TUSB incidence and severity experiment 3 was treatment (non-abrasion,

abraded and cool on day 0, delayed fruit cooled on day 1, 2 and 4). The factor for AUSB, EUSB

and TUSB incidence and severity analyses in experiment 4 was treatment (non-abrasion, abrasion,

and delayed abrasion on day 1, 2, 4 and 6). The factors for EUSB and TUSB incidence and severity

analyses in experiment 5 for fruit grown in the Northern Territory are abrasion (non-abrasion and

abrasion) and temperature (20, 12, 10, 8 and 6°C). However, the factor for AUSB incidence

analyses in experiment 5 for fruit grown in the Northern Territory is temperature (20, 12, 10, 8 and

6°C). The factor for AUSB severity analyses in experiment 5 for fruit grown in the Northern

Territory is temperature (12, 10, 8 and 6°C) because few fruit affected with AUSB. The factors for

EUSB and TUSB incidence and severity analyses in experiment 5 for fruit grown in the North

Queensland are abrasion (non-abrasion and abrasion) and temperature (20, 12, 10, 8 and 6°C). The

factors for AUSB incidence and severity analyses in experiment 5 for fruit grown in the North

Queensland are temperature (20, 12, 10, 8 and 6°C).

Repeated measurement ANOVA was used to analyse skin colour, firmness and weight loss in

experiment 5 by factors of abrasion (non-abrasion and abrasion) and temperature (20, 12, 10, 8 and

6°C). Chlorophyll fluorescence analyses were not involved in statistical analyses because similar

levels of data were observed, which is similar to the data in experiment 6. General ANOVA for

Northern Territory by one factor of temperature and repeated measurement ANOVA for North

Queensland by two factors of temperature and time, respectively, were used to analyses chlorophyll

fluorescence for experiment 6. The significance of differences between treatments was determined

using the protected Fisher test at the 5% level.

5.3 Results

5.3.1 Experiment 1. Effects of storage temperature and fruit size on abraded fruit in the 2011

– 12 season

A significant (P < 0.035) interaction of storage temperature and fruit size was found on TUSB

incidence (Table 5.1). This interaction reflected a general decrease in TUSB with increasing storage

temperature and varying responses with different fruit sizes. However, fruit size per se had no

consistent effect on TUSB incidence. Storage temperature did, however, have a significant (P <

137

0.001) effect on TUSB incidence. Fruit kept at 20°C developed a significantly (P < 0.05) lower

TUSB incidence than fruit kept at lower temperatures (≤ 16°C). Fruit kept at 20 and 13°C also

developed the least TUSB when expressed as the surface area affected. Fruit maintained at 10°C

had displayed the highest area of TUSB while fruit kept at 7 and 16°C developed moderate areas of

TUSB. Storage temperature was also found to have a significant (P < 0.001; P < 0.001) effect on

AUSB incidence and area. However, responses for storage temperature on AUSB incidence and

area were different. Fruit kept at 7 and 10°C displayed significantly (P < 0.05) higher AUSB

incidences than those at 13°C and at 16°C, while fruit kept at 20°C developed the lowest AUSB

incidence. Fruit kept at 10°C (Figure 5.3 B) developed a significantly (P < 0.05) larger area of

AUSB than fruit kept at 16°C (Figure 5.3 D), while fruit maintained at 7, 13 and 20°C (Figure 5.3 A,

C and E) developed the least AUSB area. Storage temperature was also found to significantly (P <

0.001; P < 0.001) affect EUSB incidence and area. AUSB incidence and area differed according to

the fruit storage temperature. Fruit kept at 7 and 10°C developed significantly (P <0.05) higher

EUSB incidences than fruit kept at other storage temperatures. Fruit maintained at 7°C displayed a

significantly (P <0.05) larger EUSB area than fruit kept at 10, 13, 16 and 20°C.

138

Figure 5.3 Images of USB expression on abraded ‗Honey Gold‘ mango fruit at eating ripe. Green-

mature fruit were harvested from the Northern Territory, abraded with sandpaper, maintained at 7C

(A), 10C (B), 13C (C), 16C (D) or 20C (E) for 6 days, and then transferred to 20C and 90 –

100% RH until they reached eating ripe.

A

E

D C

B

139


temperature (7, 10, 13, 16 and 20ºC) on AUSB, EUSB and TUSB incidence and severity on

abraded ‗Honey Gold‘ fruit at eating ripe. ‗Honey Gold‘ mango fruit of different sizes were

harvested from the Northern Territory in the 2011 – 12 season. They were abraded with sandpaper

and stored at different temperatures and 90 – 100% RH for 6 days prior to transfer to 20ºC and 90 –

100% RH until fruit reached eating ripe. Data are expressed as treatment means. Data followed by

the same letters are not significantly different at P = 0.05. More details are presented in Table A

3.1.

Treatments Incidence

(%)

Factor Incidence (%) Severity (cm2 affected)

TUSB AUSB EUSB TUSB AUSB EUSB

Fruit size × storage

temperature

Storage temperature (°C)

7°C, large 92 cd 7°C 98 c 76 b 21.99 b 9.75 a 14.73 b

7°C, medium 100 d 10°C 98 c 79 b 41.41 c 33.40 c 6.56 a

7°C, small 100 d 13°C 83 b 14 a 6.37 a 6.02 a 3.91 a

10°C, large 92 cd 16°C 90 b 14 a 18.76 b 18.21 b 4.37 a

10°C, medium 100 d 20°C 17 a 14 a 3.99 a 4.24 a 4.25 a

10°C, small 100 d

13°C, large 67 b

13°C, medium 79 bc

13°C, small 81 bc

16°C, large 100 d

16°C, medium 100 d

16°C, small 93 cd

20°C, large 33 a

20°C, medium 21 a

20°C, small 25 a

Factors generalized linear model with logistic regression on incidence and conditional unbalanced

analysis of variance on area

Temperature *** Temperature *** *** *** *** ***

Fruit size NS Fruit size NS NS NS NS NS

Fruit size ×

temperature

* Fruit size ×

temperature

NS NS NS NS NS

140



5.3.2 Experiment 2. Effects of storage duration at 13°C and fruit size on abraded fruit in the

2011 – 12 season

A significant (P = 0.012; P = 0.033; P = 0.003) interaction of fruit size and storage duration was

found for AUSB, EUSB and TUSB incidence (Table 5.2). Fruit stored at 13ºC for 9 days developed

significantly (P < 0.05) higher TUSB, AUSB and EUSB incidences than fruit held at 13ºC for 1 day

(Table 5.2). As the storage duration increased, the surface area on fruit affected by TUSB, AUSB

and EUSB area increased (Table 5.2).

141

5.3.3 Experiment 3. Effect of delayed cooling in the 2011 – 12 season

Table 5.2 Effects of fruit size (large [12 / tray], medium [14 / tray] and small [16 / tray]) and

storage duration (1, 3, 6 and 9 days) at 13°C on abraded fruit AUSB, EUSB and TUSB incidence

and severity (area) on ‗Honey Gold‘ mango fruit at eating ripe (n = 12, 14 and 16). Fruit of

different sizes were harvested from the Northern Territory in the 2011 – 12 season. They were

abraded with sandpaper and stored at different temperatures and 90 – 100% RH for 6 days prior

to transfer to 20ºC and 90 – 100% RH until fruit reached eating ripe. Data are expressed as

treatment means. Data followed by the same letters are not significantly different at P = 0.05.

More details are presented in Table A 3.15.

Treatments Incidence (%) Factor Severity (cm2 affected)

TUSB AUSB EUSB TUSB AUSB EUSB

Duration × fruit size Duration (days)

1, large 67 a 67 a 0 a 1 11.14 a 6.02 a 4.45 ab

1, medium 79 ab 79 ab 14 abc 3 28.49 b 19.41 b 3.29 a

1, small 100 c 100 c 25 bcd 6 44.33 c 36.92 c 7.70 b

3, large 100 c 100 c 50 cd 9 46.46 d 37.32 c 8.96 b

3, medium 93 bc 93 bc 21 abcd

3, small 88 b 88 ab 25 bcd

6, large 100 c 92 bc 50 cd

6, medium 100 c 100 c 50 d

6, small 88 b 88 ab 6 ab

9, large 92 bc 92 bc 25 abcd

9, medium 100 c 93 bc 57 d

9, small 100 c 100 c 50 d

Factors generalized linear model with logistic regression analysis of variance and conditional

factors analysis of variance

Duration NS NS * Duration *** *** *

Fruit size NS NS NS Fruit size NS NS NS

Duration × fruit

size

* * ** Duration × fruit

size

NS NS NS

*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant (P

< 0.001); NS: not significant.

142

There was no significant (P =0.05) effect of delaying the fruit cooling process on AUSB, EUSB and

TUSB incidence (Table A 3.16). However, a significant (P = 0.014) effect of delay the fruit cooling

was found on AUSB and TUSB affected areas on the fruit treated (Table 5.3). The treatment of

delayed cooling to day 4 resulted in significantly (P < 0.05) fewer TUSB and AUSB developed on

fruit as compared to fruit that were cooled on days 0 and 1.

5.3.4 Experiment 4. Effects of delayed abrasion test in the 2011 – 12 season

There was no significant (P = 0.05) effects of delaying the abrasion test in terms of AUSB, EUSB

and TUSB incidence and severity (Table A 3.17).

Table 5.3 Effects of delayed cooling of fruit on days 0, 1, 2 and 4 on the severity of EUSB and

TUSB (n = 5) on ‗Honey Gold‘ fruit at eating ripe. Fruit were harvested from the North Queensland

collected in the 2011 – 12 season. The fruit were abraded with sandpaper and then kept in a

ripening room at 20°C and 90 – 100% RH for zero or one or two or four days. They were then kept

in a cold room at 13°C and 90 – 100% RH for six days. Fruit with no abrasion kept at 13°C for six

days were the controls. All fruit were finally moved to the ripening room until fruit reached eating

ripe. Data are expressed as treatment means. Data followed by the same letters are not significantly

different at P = 0.05. More details are presented in Table A 3.16.

Treatments TUSB severity

(cm2 area affected)

AUSB severity

(cm2 area affected)

Non-abrasion, 13°C 1.91 a 1.91 ab

Abrasion on day 0, and kept at 13°C on day 0 6.42 bc 6.16 bc

Abrasion on day 0, and kept at 13°C on day 1 8.57 c 7.95 c

Abrasion on day 0, and kept at 13°C on day 2 2.56 ab 2.07 ab

Abrasion on day 0, and kept at 13°C on day 4 1.73 a 1.73 a

Conditional factors analysis of variance

Treatment * *



143

5.3.5 Experiment 5. Effects of storage temperature, fruit growing region and abrasion test in

the 2012 – 13 season

Fruit grown in the Northern Territory developed a higher USB incidence than did those produced in

North Queensland (Table 5.4 and Table 5.5). Fruit grown in Southeast Queensland developed very

little USB (Table 5.6). Thus, the sensitivity of ‗Honey Gold‘ fruit to developing USB appeared to

vary considerably across different production regions.

Figure 5.4 Images of abraded ‗Honey Gold‘ mango fruit at eating ripe. A. Green-mature fruit were

harvested from the Northern Territory (A), North Queensland (B) and Southeast Queensland (C),

abraded with sandpaper and maintained at 10ºC and 90 – 100% RH for 8 days and then transferred

to 20ºC and 90 – 100% RH until they were eating ripe.

5.3.5.1 USB incidence and severity

Significant (P < 0.05) interactions were found for the incidence and severity of TUSB, AUSB and

EUSB on fruit grown in the Northern Territory (Table 5.4). A significant (P = 0.039) interaction of

A B

C

144

abrasion and storage temperature was found for TUSB incidence on abraded and non-abraded fruit.

The interaction reflected a general decrease in TUSB with increasing storage temperature and

varying responses of fruit to the abrasion test. Fruit kept at 20°C developed no or a low TUSB

incidence with or without abrasion. Abraded fruit kept at 12°C had a significantly (P < 0.05) higher

TUSB incidence than did non-abraded fruit maintained at the same temperature. Storage

temperature was found to have a significant (P = 0.004) effect on abraded fruit for AUSB incidence.

Fruit kept at different temperatures developed different levels of AUSB incidence. Abraded fruit

kept at 20°C developed a significantly (P < 0.05) lower AUSB incidence than fruit maintained at

the other storage temperatures (6, 8, 10 and 12°C). Storage temperature was found to have a

significant (P < 0.001) effect on EUSB incidence of abraded and non-abraded fruit. Fruit kept at

different temperatures developed different levels of EUSB incidence. Low temperatures (≤ 10°C)

significantly (P < 0.05) increased EUSB incidence. Storage temperature was found to have a

significant (P = 0.024; P = 0.040) effect on TUSB and AUSB severity. TUSB and AUSB severity

on fruit kept at 20°C were not included in the statistical analyses because of limited data on TUSB

and AUSB area. Fruit maintained at 10°C displayed a significantly (P < 0.05) larger TUSB area

than fruit kept at 6 and 12°C (Table 5.4). Fruit kept at 10°C had a significantly (P < 0.05) larger

AUSB area than fruit held at 6, 8 and 12°C.

145

Table 5.4 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on AUSB, EUSB and TUSB incidence and severity (cm2 affected)

on ‗Honey Gold‘ fruit at eating ripe. Fruit were harvested from the Northern Territory during the 2012 – 13 season. The fruit were abraded or not

abraded with sandpaper, and then kept at different temperatures for eight days. All fruit were finally kept in the ripening room at 20°C and 90 –

100% RH until they reached eating ripe. Data are expressed as treatment means. Data followed by the same letters are not significantly different at P

= 0.05. NS: non-significant. More details are presented in Table A 3.2.

Treatments Incidence

(%)

Factor Incidence

(%)

Factor Incidence

(%)

Factor Severity Factor Severity

TUSB AUSB EUSB TUSB AUSB

Abration × storage temperature Storage temperature Storage temperature Storage temperature Storage temperature

No abrasion, 6°C 40 cd 6°C 47 b 6°C 33 b 6°C 3.05 a 6°C 3.3 b

Abrasion, 6°C 53 cd 8ºC 53 b 8ºC 36 b 8ºC 6.90 bc 8ºC 5.9 b

No abrasion, 8ºC 47 cd 10°C 67 b 10°C 40 b 10°C 10.59 c 10°C 11.0 a

Abrasion, 8ºC 60 cd 12°C 60 b 12°C 7 a 12°C 3.10 ab 12°C 2.9 b

No abrasion, 10°C 27 bc 20°C 7 a 20°C 0 a 20°C 2.62 20°C 2.62na

Abrasion, 10°C 67 cd

No abrasion, 12°C 0 a

Abrasion, 12°C 60 cd

No abrasion, 20°C 0 a

Abrasion, 20°C 7 ab

Factors generalized linear model with logistic regression on incidence and conditional unbalanced analysis of variance on area

Abrasion *** Abrasion NS Abrasion NS

Storage *** Storage ** Storage *** Storage * Storage *

146

temperature temperature temperature temperature temperature

Storage

temperature ×

Abrasion

* Storage

temperature ×

Abrasion

NS Storage

temperature ×

Abrasion

NS

*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant (P < 0.001); na: not analysed; NS: not significant.

147

The treatment response of fruit grown in North Queensland was different from that of fruit

produced in the Northern Territory. Abrasion was found to cause significantly (P = 0.002) higher

incidence of TUSB relative to fruit that were not abraded (Table 5.5).

Few fruit from Southeast Queensland showed symptoms of USB (Table 5.6). For example, only 7%

of the abraded fruit held at the lowest temperature of 6°C developed TUSB, AUSB and EUSB

(Table 5.6).

Table 5.5 Effect of abrasion test on TUSB incidence on ‗Honey Gold‘ fruit at eating ripe (n = 15).

Fruit grown in North Queensland were either abraded with sandpaper or not abraded, and then kept

at different storage temperatures for eight days. Fruit were finally kept in a ripening room at 20°C

and 90 – 100% RH until fruit reached eating ripe. Data are expressed as treatment means. Data

followed by the same letters are not significantly different at P = 0.05. More details are presented in

Table A 3.3.

Factor TUSB Incidence (%)

Abrasion

No abrasion 5 a

Abrasion 21 b

Factors generalized linear model of binomial logistic regression on incidence

Temperature NS

Abrasion **

Temperature × abrasion NS



148

5.3.5.2 Chlorophyll fluorescence, skin colour, firmness and weight loss

Similar levels of skin chlorophyll fluorescence (Fv / Fm) were found on fruit kept at all temperatures

except 20°C from days 0 to 8 (Table A 3.4). Chlorophyll fluorescence of fruit kept at 20°C

decreased to below 0.7 on days 5 and 8.

Different significant (P < 0.05) interactions were found for skin colour on fruit grown in three

regions (viz, the Northern Territory, North Queensland and Southeast Queensland) (Figure 5.5). A

significant (P < 0.001) interaction of time, storage temperature and abrasion was found for skin

Table 5.6 Summary of abrasion and storage temperature (6, 8, 10, 12 and 20°C) on the incidence

and severity of AUSB, EUSB and TUSB at eating ripe (n = 15). ‗Honey Gold‘ mango fruit grown

in Southeast Queensland were either abraded with sandpaper or not abraded, and then kept in rooms

at 6, 8, 10, 12 and 20°C, and 90 – 100% RH for eight days. Fruit were then kept in a ripening room

at 20°C and 90 – 100% RH until fruit reached eating ripe. All treatments were not involved in

analysis because few fruit were affected with USB. Data are expressed as treatment means.

Factors TUSB AUSB EUSB

Incidence

(%)

Severity

(cm2

affected)

Incidence

(%)

Severity

(cm2

affected)

Incidence

(%)

severity

(cm2

affected)

No abrasion,

6°C

0 0 - - 0 0

Abrasion, 6°C 13 2.50 7 5.46 7 0.44

No abrasion,

8ºC

0 0 - - 0 0

Abrasion, 8ºC 7 5.81 7 2.51 0 0

No abrasion,

10°C

0 0 - - 0 0

Abrasion, 10°C 0 0 0 0 0 0

No abrasion,

12°C

0 0 - - 0 0

Abrasion, 12°C 0 0 0 0 0 0

No abrasion,

20°C

0 0 - - 0 0

Abrasion, 20°C 0 0 0 0 0 0

149

colour on fruit from the Northern Territory (Figure 5.5 A). Skin colour of fruit that were either

abraded or not abraded increased with different trends depending upon storage temperature. Fruit

kept at low temperature ≤ 12°C developed significantly (P < 0.05) less skin colour than fruit kept at

20°C at any time across the experiment. A significant (P < 0.001) interaction of time and storage

temperature was found for skin colour on fruit from North Queensland and Southeast Queensland

(Figure 5.5 B and C). Fruit kept at 20°C had consistently significantly (P < 0.05) higher skin colour

than fruit kept at other temperatures of ≤ 12°C. A significant (P = 0.005) interaction of time and

abrasion was found for skin colour on fruit from Southeast Queensland (Figure 5.5 D). Skin colour

for abraded and non-abraded fruit crossed over across sequential times. However, the differences

between abrasion and non-abrasion treatments were not significant (P = 0.05) at any time.

150

Figure 5.5 A: A significant (P < 0.001) interaction of time, abrasion and temperature for skin colour

of fruit grown in the Northern Territory (n = 15); B: A significant (P < 0.001) interaction of time

and temperature for skin colour of fruit grown in North Queensland (n = 30); C and D: Significant

(P < 0.001; P = 0.005) interactions of time and temperature (C) (n = 30) and of time and abrasion

(D) (n = 75) for skin colour of fruit grown in Southeast Queensland. ‗Honey Gold‘ mango fruit

harvested from the Northern Territory, North Queensland or Southeast Queensland collected in the

2012 – 13 season. The fruit were either abraded with sandpaper or not abraded, and subsequently

kept in different rooms operating at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH for eight days.

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

No abrasion, 6ºC

No abrasion, 8ºC

No abrasion, 10ºC

No abrasion, 12ºC

No abrasion, 20ºC

Abrasion, 6ºC

Abrasion, 8ºC

Abrasion, 10ºC

Abrasion, 12ºC

Abrasion, 20ºC

LSD

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

6ºC

8ºC

10ºC

12ºC

20ºC

LSD

LSD

0 2 4 6 8 10 12 14

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

Time from abrasion (days)

0 2 4 6 8 10 12 14

Skin

co

lou

r (0

- 6

)

0

1

2

3

4

5

6

No abrasion

Abrasion

LSD

A B

C D

DB and CA

151

Different significant (P < 0.05) interactions were found regarding the firmness of fruit grown in the

three regions of the Northern Territory, North Queensland and Southeast Queensland (Figure 5.6).

A significant (P < 0.001) interaction of time, storage temperature and abrasion was found for the

firmness of fruit from the Northern Territory (Figure 5.6 A). Fruit kept at 20°C displayed

significantly (P < 0.05) higher firmness score data (i.e. greater softening) than that of fruit kept at

other temperatures of ≤12°C at a given time in the experiment. Firmness of abraded and non-

abraded fruit kept at 20°C crossed over across sequential times. A significant (P < 0.001; P < 0.001)

interaction of time and storage temperature was found for the firmness of fruit from North

Queensland and Southeast Queensland (Figure 5.6 B and D). Fruit kept at 20°C displayed

significantly (P < 0.05) higher firmness score data than that of fruit kept at other temperatures of ≤

12°C. A significant (P = 0.024) interaction of time and abrasion was found for the firmness of fruit

from Southeast Queensland (Figure 5.6 C). Firmness of abraded and non-abraded fruit crossed over

across sequential times. However, the differences between abrasion and non-abrasion treatments

were not significant (P = 0.05) at any time.

Different significant (P < 0.05) interactions were found for weight loss from fruit grown in the three

regions (Figure 5.7). Significant (P < 0.001, P = 0.002, P < 0.001) effects of time (Figure 5.7 A),

storage temperature (Figure 5.7 B) and abrasion (Figure 5.7 C) were found on weight loss from fruit

grown in the Northern Territory. Fruit weight loss increased with increasing time. Weight loss also

increased with increasing storage temperature. There was also an increase in weight loss from

abraded fruit as compared to non-abraded fruit. Significant (P < 0.05) interactions of time and

abrasion (Figure 5.7 D) and of time and storage temperature (Figure 5.7 E) were found for weight

loss for fruit grown in North Queensland. Weight loss of abraded fruit increased more than it did for

non-abraded fruit across sequential times (Figure 5.7 E). Weight loss from abraded fruit were

significantly (P < 0.05) higher than that for non-abraded fruit at any time from day 4. Weight loss

from fruit kept at 20°C were greater than for fruit maintained at 12 and 10°C, and higher than for

fruit held at 6 and 8ºC from days 4 to 8. Fruit kept at 20°C had significantly (P < 0.05) higher

weight loss than did fruit kept at 12 and 10°C from day 4. A significant (P < 0.001) interaction of

time, abrasion and storage temperature was found for weight loss (Figure 5.7 F). Rates of weight

loss from abraded fruit maintained at 20°C were greater than from non-abraded fruit kept at 20°C

across sequential times. Abraded fruit kept at 20°C lost significantly (P < 0.05) more weight loss

than did non-abraded fruit maintained at 20°C for different times.

All fruit were kept in a ripening room at 20°C and 90 – 100% RH until they reached eating ripe.

More details are presented in Table A 3.5, Table A 3.6 and Table A 3.7.

152

Figure 5.6 A: A significant (P = 0.036) interaction of time, abrasion and temperature was

determined for firmness of fruit grown in The Northern Territory (n = 15); B: A significant (P <

0.001) interaction of time and temperature for firmness of fruit grown in North Queensland (n =

30); C and D: Significant (P < 0.001, P = 0.024) interactions of time and temperature (C) (n = 30)

and of time and abrasion (D) (n = 75) for firmness of fruit grown in Southeast Queensland. After

‗Honey Gold‘ mango fruit being harvested from the Northern Territory and North Queensland, fruit

were either abraded with sandpaper or not abraded. They were then kept at different rooms

Fir

mnes

s (0

- 4

)

0

1

2

3

4No abrasion, 6ºC

No abrasion, 8ºC

No abrasion, 10ºC

No abrasion, 12ºC

No abrasion, 20ºC

Abrasion, 6ºC

Abrasion, 8ºC

Abrasion, 10ºC

Abrasion, 12ºC

Abrasion, 20ºC

LSD

Fir

mnes

s (0

- 4

)

0

1

2

3

4

6ºC

8ºC

10ºC

12ºC

20ºC

LSD

LSD

A

B

C

Time from abrasion (days)

0 2 4 6 8 10 12 14

Fir

mnes

s (0

- 4

)

0

1

2

3

4No abrasion, 6ºC

No abrasion, 8ºC

No abrasion, 10ºC

No abrasion, 12ºC

No abrasion, 20ºC

Abrasion, 6ºC

Abrasion, 8ºC

Abrasion, 10ºC

Abrasion, 12ºC

Abrasion, 20ºC

153

operating at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH for eight days. Fruit were finally kept in

the ripening room at 20°C and 90 – 100% RH until they reached eating ripe. More details are

presented in Table A 3.8, Table A 3.9 and Table A 3.10.

154

Figure 5.7 A, B and C: Significant (P < 0.001; P = 0.002, P < 0.001) effects of time (A) (n = 150),

EF

d

c

b

a

a

b

bcbc

c

Time from abrasion test (days)

0 2 4 6 8 10 12 14

Wei

ght

loss

(%

)

0

1

2

3

Temperature (ºC)

6 8 10 12 20

Wei

ght

loss

(%

)

0

1

2

3

a

A B

C


0 2 4 6 8 10 12 14

Wei

ght

loss

(%

)

0

1

2

3

4

5

6

No abrasion, 6ºC

No abrasion, 8ºC

No abrasion, 10ºC

No abrasion, 12ºC

No abrasion, 20ºC

Abrasion, 6ºC

Abrasion, 8ºC

Abrasion, 10ºC

Abrasion, 12ºC

Abrasion, 20ºC


0 2 4 6 8 10 12 14

Wei

ght

loss

(%

)

0

1

2

3

4

5

6ºC

8ºC

10ºC

12ºC

20ºC

LSD

LSD


0 2 4 6 8 10 12 14

Wei

ght

loss

(%

)

0

1

2

3

4

No abrasion

Abrasion

LSD

D

Abrastion test

No abrasion Abrasion

Wei

ght

loss

(%

)

0

1

2

3

b

FD E

155


season

Temperatures between 0 and 30°C did not significantly (P < 0.05) affect the ratio of Fv and Fm on

mango fruit skin discs from fruit harvested in the Northern Territory and North Queensland (Table

A 3.14). Moreover, no USB was observed on mango fruit skin discs from the Northern Territory

and North Queensland.

5.4 Discussion

The sensitivity of ‗Honey Gold‘ mango fruit to developing USB in response to the abrasion test and

to varying different storage temperatures varied with the growing region. Fruit produced in the

relatively hotter tropical climate of Northern Territory were the most susceptible to developing USB

(Table 5.4). Those grown in cooler tropical climate of North Queensland were moderately

susceptible to this disorder (Table 5.5). Fruit produced in the cooler sub-tropical climate of

Southeast Queensland were largely resistant to developing USB (Table 5.6). Other browning in

terms of watercore in ‗Fuji‘ apple fruit (Harker et al., 1999) and internal browning in ‗Conference‘

pear fruit (Franck et al., 2007) have also been reported to be influenced by the growing region. It is

suggested that undefined factors of edaphic conditions in orchards might account for different

susceptibility to browning between regions (Harker et al., 1999, Franck et al., 2007).

Exposure to the low temperatures of ≤ 10°C were associated with a higher EUSB incidence on

‗Honey Gold‘ mango fruit grown in the Northern Territory (P = 0.05) than was exposure at

temperatures of 12 and 20°C (Table 5.1 and Table 5.4). However, the effects of the low

temperatures of ≤ 10°C on the EUSB severity were not consistent in two mango seasons (Table 5.1

temperature (B) (n = 120) and abrasion (C) (n = 300) on weight loss (%) of fruit grown in the

Northern Territory; D and E: Significant (P < 0.001, P < 0.001) interactions of time and abrasion (n

= 30) and of time and abrasion (n = 30) for weight loss of fruit grown in North Queensland; F: A

significant (P < 0.001) interactions of time, abrasion and temperature for weight loss (%) of fruit

grown in Southeast Queensland (n = 15). After ‗Honey Gold‘ mango fruit being harvested from The

Northern Territory and North Queensland, fruit were either abraded with sandpaper or not abraded.

They were then kept in different rooms operating at 6 or 8 or 10 or 12 or 20°C, and 90 – 100% RH

for eight days. Fruit were finally kept in ripening room at 20°C and 90 – 100% RH until they

reached eating ripe. More details are presented in Table A 3.11, Table A 3.12 and Table A 3.13.

156

and Table 5.4). In the 2011- 12 mango season, the low temperature of 7°C caused a significant

larger area of EUSB than other temperatures (Table 5.1). However, low temperatures of 6°C and

8°C were found not to significantly influence EUSB severity compared to other temperatures in the

2012 – 13 mango season (Table 5.4). Chlorophyll fluorescence (Fv / Fm), a parameter indicating

chilling, was found to be present at similar levels on chilled mango fruit grown in the Northern

Territory and North Queensland. The chilling temperature for mango fruit is generally 12 – 13°C

(González-Aguilar et al., 2001). However, USB was found to occur surrounding the abrasion

position at 16°C. In addition, USB occurred on abraded fruit grown in Northern Territory at 12°C,

but not USB occurred on fruit that were not abraded (Table 5.4). Therefore, USB is not a simply

chilling injury.

The AUSB incidence was generally higher than the EUSB incidence in fruit exposed to low

temperature. The abrasion test consistently and significantly (P < 0.001; P = 0.002) increased

TUSB incidence of fruit grown in the Northern Territory and North Queensland (Table 5.1 and

Table 5.4). Although a significant interaction of the abrasion test and fruit size was found on fruit

grown in the Northern Territory, fruit size did not consistently increase or decrease the incidence of

total USB. Therefore, abrasion is most likely a direct factor related to USB. The disruption of

mango fruit resin ducts can result in toxic compounds in the sap, such as terpinolene leaking from

the stress zone and potentially damaging surrounding cells (Loveys et al., 1992, Crisosto et al.,

1993, Medeira et al., 1999) and / or rendering them less tolerant to low temperature.

Under-skin browning was expressed on ‗Honey Gold‘ mango fruit away from abrasion position in

terms of small area. As to the cause of EUSB, physical pressure and / or vibration (rubbing) stress

may arise from fruit-to-fruit contact, fruit-to-fibreboard tray contact, and fruit-to-liner contact

during handling and transportation (Marques, 2012). Adverse consequences of postharvest handling

and transportation practices on bruising of apple (Vursavus and Ozguven, 2004), pear (Berardinelli

et al., 2005) and loquat (Barchi et al., 2002) fruit have been reported.

Low storage temperature did not influence EUSB severity. However, storage temperature was

found to be related to the severity of AUSB. Since the severity of AUSB contributes largely to the

severity of TUSB, storage temperature was also found to be related to the severity of TUSB.

Exposure of fruit to 10°C caused the greatest severity of AUSB and TUSB when compared to other

temperatures (6, 8, 12 and 20°C) (Table 5.1 and Table 5.4). The duration of low storage temperature

was closely related to AUSB (Table 5.2). AUSB severity increased with increasing duration of low

temperature storage (Table 5.2). Similar to AUSB severity, TUSB severity also increased with

157

increasing duration of low temperature storage (Table 5.2). Fruit size was not related to EUSB,

AUSB and TUSB severity (Table 5.1).

Different significant interactions were found on skin colour, firmness and weight loss for fruit

grown in the three regions. Exposure to low temperature (12°C) obviously extends shelf life by

delaying skin colour change, fruit softening and weight loss. Similar effects of low temperature

were reported on loquat (Cai et al., 2006) and litchi (Sivakumar et al., 2005) fruit. The abrasion test

did not consistently affect skin colour and firmness. However, it was found to increase rates of

weight loss than non-abraded fruit from the three regions.

5.5 Conclusion

This study highlighted that the fruit growing region is an important factor influencing USB

incidence. In response to the skin abrasion test and low storage temperature treatments, fruit grown

in the warmer climate of the Northern Territory were more susceptible to developing USB than

were fruit grown in North Queensland. Moreover, fruit grown in the relatively cooler climate of

Southeast Queensland developed very little USB. Fruit subjected to the abrasion test and held at low

temperatures of ≤ 16°C developed a high incidence of USB as compared to those held at 20°C. As a

putative indicator of chilling injury, similar levels of the Fv / Fm chlorophyll fluorescence parameter

of fruit skin were found during the development of USB at low storage temperatures. These

findings suggested that USB is not a simply chilling injury. Rather, it is most likely to be induced

by mechanical stress (e.g. the abrasion test) and intensified by low temperature storage. USB was

observed in positions on the fruit distant from the abrasion point at low temperatures of ≤ 10°C.

These relatively distant points may represent small areas subject to pressures such as fruit contact

with other fruit or the fibreboard tray or tray liner. Overall, physical and temperature stresses play

roles in inducing USB which occurs during commercial transportation. USB is most likely induced

by vibration and could be intensified by low temperature as will be examined further in Chapter 6.

Therefore, simulated vibration combined with low temperature, and polystyrene liner instead of

polyethylene liner are worth trying, which will be examined further in Chapter 6.

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technology: damage to loquats by vibration-simulating intra-state transport. Biosystems

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Bolhar-Nordenkampf, H., Long, S., Baker, N., Oquist, G., Schreiber, U. and Lechner, E. 1989.

Chlorophyll fluorescence as a probe of the photosynthetic competence of leaves in the field:

a review of current instrumentation. Functional Ecology, 497-514.

Cai, C., Xu, C., Shan, L., Li, X., Zhou, C., Zhang, W., Ferguson, I. and Chen, K. 2006. Low

temperature conditioning reduces postharvest chilling injury in loquat fruit. Postharvest


Crisosto, C. H., Johnson, R. S., Luza, J. and Day, K. 1993. Incidence of physical damage on peach

and nectarine skin discoloration development: Anatomical studies. Journal of the American

Society for Horticultural Science, 118: 796-800.

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160

Effect of Simulated Vibration on USB of ‘Honey Gold’ Chapter 6

Mango Fruit and the Browning Biochemistry of the USB Response

Abstract

Under-skin browning disorder on ‗Honey Gold‘ mango fruit skin is most likely induced by abrasion

and could be intensified by low storage temperature (Chapter 5). Three experiments were conducted

to study the effects of fruit growing region, duration at 12 Hz of simulated vibration, storage

temperature and tray insert on USB incidence and severity. Other fruit quality parameters also were

assessed including skin colour, firmness and weight loss in one sub-experiment. Browning

biochemistry (viz., total phenolics concentration, polyphenol oxidase [PPO] and peroxidase [POD]

activities) was also investigated. Vibration for relatively long durations (9 and 18 h) of fruit in the

polyethylene liner tended to induce a higher incidence of USB. Low temperature (12°C) further

increased the incidence. It is suggested that physical stress is directly inducing USB and low

temperature can intensify this disorder. Contrary to expectations, the polystyrene liner had no

consistent effect on reducing USB as compared to the polyethylene liner. That may have been due

to the low profile of the liner allowing more movement and contact between fruit, and with the tray

side. Total phenolics concentration and PPO and POD activities in mango skin tissue were not

directly associated with USB expression. Overall, physical stress (vibration) is the factor directly

inducing USB by causing sap underneath epidermal cells leak from resin ducts to surrounding cells

and the toxic compounds of sap damaged cells membrane, which makes PPO in skin tissue contact

to phenolics and finally causes browning.

Keyword: enzymes activity, ‗Honey Gold‘ mango fruit, low storage temperature, phenolics, quality

parameter, simulated vibration

6.1 Introduction

Under-skin browning (USB) is a skin browning disorder on ‗Honey Gold‘ mango fruit that is

manifested as discolouration under the epidermis (Hofman et al., 2009, Marques, 2012). The

symptoms are generally similar to chilling injury resulting from low storage temperature of < 12 –

10oC. However, USB was also observed when fruit are held at temperatures as high as 16°C

(Chapter 5). The incidence of USB was found to be evidently dependent upon growing region

(Chapter 5). Fruit grown in the Northern Territory (tropics) were relatively more susceptible to USB

than are fruit grown in North Queensland (subtropics). In stark contrast, USB has not been observed

161

on ‗Honey Gold‘ fruit grown in Southeast Queensland (Chapter 5). Therefore, USB is most likely

directly related to physical stress, such as abrasion and intensified by low temperature (Chapter 5).

Observations of commercial refrigerated consignments road-freighted from the Northern Territory

to Brisbane (a 3-day road journey) often revealed physical damage caused by fruit rubbing against

the plastic tray insert or the side of the fibre board tray. Vibration is one major physical stress which

could cause USB for harvested fruit during transportation. Mechanical stresses such as vibration

after harvest, have been reported to cause damage for many fruits including mango by damaging

epidermal and sub-epidermal cells (Kader, 1989). Vibration during transportation caused damage

on ‗Huanghua‘ pear skin, affecting the plasma membrane integrity of skin cells (Zhou et al., 2007).

Either vibration during transportation or simulated vibration have been reported to cause

mechanical damage to tomato (Olorunda and Tung, 1985), and ‗Abate‘ pear (Berardinelli et al.,

2005), loquat (Barchi et al., 2002) and ‗solo‘ papaya (Quintana and Paull, 1993) fruits.

Phenylpropanoid metabolism can be triggered by physical stress (Tomás-Barberán et al., 1997,

Saltveit, 2000) and resulted in synthesis of phenolics. These phenolics react with polyphenol

oxidase and / or peroxidase resulting in enzymatic browning.

In the present work, it is hypothesised that USB can be induced by vibration during transportation

and intensified by low storage temperature. It is further hypothesised that USB in ‗Honey Gold‘

mangoes results from the enzymatic oxidation of phenolics by PPO and POD. To establish the role

of vibration damage and low storage temperature in USB, fruit from the Northern Territory and

North Queensland were treated with simulated vibration for different durations (0, 3, 9 and 18 h) at

different storage temperatures (12 and 20°C) in different liners (polystyrene and polyethylene).

USB incidence and severity were evaluated along with other quality parameters (skin colour,

firmness, weight loss). Biochemical attributes (PPO and POD activities and total phenolics

concentration) were also measured to establish the role of enzymatic browning in USB.


6.2.1 Fruit materials

Green mature ‗Honey Gold‘ mango fruit were commercially harvested from a farm near Fox Road

in Katherine, Northern Territory, Australia (14°27‘S, 132°15‘E) in November, and from a farm near

Mutchilba in North Queensland, Australia (17°8‘S, 145°12‘E) in early January during the 2012 – 13,

2013 – 14 and 2014 – 15 seasons. They were taken to a nearby packinghouse and treated and

162



2010). All fruit packed into single layer fibreboard trays with polystyrene liners and two layers of

bubble wrap on top of the fruit to prevent compression injury. Fruit grown in the Northern Territory

and North Queensland were air-freighted to Brisbane airport within 24 – 36 h. From there, they

were then transported by car to the postharvest laboratory at the Ecosciences Precinct at Brisbane,

QLD, Australia or to the Maroochy Research Station at Nambour, QLD, Australia within 1 – 2 h.

Upon arrival in the laboratory, all fruit were completely randomly assigned to treatments.

6.2.2 Vibration calibration

A vibration table (EQ 21857, Windsor, RL Windsor & Son Pty Ltd., QLD, Australia, Figure 6.1)

was calibrated by digital camera (Fastcam Ultima 512, Photron, Tokyo, Japan) using a live record

setting with a 250 fps frame rate in Photron FASTCAM Viewer (Photron, Tokyo, Japan).

Recordings were made under 0, 25 and 50 kg loads on the vibration table at geared settings of 0.2,

0.4, 0.6, 0.8 and 1 × 103 rpm / min using the method above with three replicate times. The

amplitude and frequency were measured at the different speeds under different loads in Photron

FASTCAM Viewer. The amplitude and frequency were different at different speeds, but did not

vary among the different loads on the vibration table (Figure 6.2). The speed setting of the vibration

table was checked by a digital laser tachometer (TL 9936, JEM tools, China). An Impact Recording

Device (SN 634 Techmark Inc., Lansing, MI, USA) was placed into the middle of the fibreboard

tray with fruit inside in the first layer during vibration to record any events of impact. The impact

recording device determined the vibration accelerations of 17 – 32 g for fruit the first layer.

According to Slaughter et al. (1993) and Shahbazi et al. (2010) report on more fruit damage occurs

in the upper position because of higher levels of acceleration, the vibration accelerations of fruit on

the second layer should be > 17 – 32 g (not measured).

163

Figure 6.1 Image of vibration table for fruit treatments

Figure 6.2 Recorded calibration frequencies (Hz) and amplitudes (cm) for the vibration table

carrying 0, 25 and 50 kg loads.

0.0 0.2 0.4 0.6 0.8 1.0

Am

pli

tud

e (c

m)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.60

25 Kg

50 Kg

Speed (x 103 rpm / min)

0.0 0.2 0.4 0.6 0.8 1.0

Fre

qu

ency

(H

z)

0

2

4

6

8

10

12

14

160

25 Kg

50 Kg

164

Figure 6.3 Images of tray inserts used in the vibration table experiments; black: polyethylene liner;

pink: polystyrene liner.

6.2.3 Experiment 1. Effects of fruit growing region, vibration duration, storage temperature

and tray insert in the 2012 – 13 season

Green mature ‗Honey Gold‘ mango fruit were harvested from a farm near Fox Road in Katherine,

Northern Territory, Australia (14°27‘S, 132°15‘E) in November, 2012 and from a farm near

Mutchilba in North Queensland, Australia (17°8‘S, 145°12‘E) in early January, 2013 following the

procedures described in Section 6.2.1. Rectangular fibreboard trays containing the fruit were fixed

to the vibration table using an iron nail peg at each corner. A single layer on a vibration table was

used for the treatments in this experiment. Fruit were treated in a cold room at 12°C and 90 – 100%

RH with 12 Hz vibration for 3 or 9 h using one of two different liners (polyethylene and polystyrene

[Figure 6.3]). After vibration treatments, all fruit were kept in the cold room for eight days and then

moved to a ripening room at 20°C and 90 – 100% RH until the fruit reached eating ripe. The control

fruit were not exposed to vibration using polyethylene liners and kept at rooms of different

temperature (12 and 20°C) and 90 – 100% RH for eight days in total, and then moved to the

ripening room until fruit reached eating ripe. Sixteen individual fruit replicates per treatment were

used in this experiment. Individual fruit was taken as the replicate.

165

6.2.4 Experiment 2. Effects of vibration duration, storage temperature and tray insert (fruit

grown in North Queensland) in the 2013 – 14 season

Green mature ‗Honey Gold‘ mango fruit were harvested from a farm near Mutchilba, North

Queensland, Australia in January, 2014 following the procedures described in Section 6.3.1.

The 12°C treatments were initially carried out, followed by the 20°C treatments. For each

temperature treatment, the fruit were vibrated at 12 Hz for 0, 3, 9 or 18 h (Figure 6.6). Two layers

on the vibration table were used in this experiment. Hard paperboard was used to divide each tray

into two parts; one half with a polystyrene liner and the other half with polyethylene liner. Because

of limited area of the vibration table, the treatments of 3 and 18 h were commenced initially, and

then the treatments of 9 h were started after the treatments of 3 h finished. The fruit in the 3 h

treatment group were spread over the first (1 tray) and second (2 trays) layers of the vibration table.

The fruit in the 18 h treatment group were also spread over the first (2 trays) and second (1 tray)

layers of the table. After 3 h of vibration, the 3 h treatment group fruit were removed, and replaced

with the 9 h treatment group. After 9 h of vibration, spare non-experimental fruit were placed in the

position of fruit vibrated for 9 h and the process was continued until the treatment of 18 h vibration

finished. After vibration treatments, the fruit vibrated at 12 and 20°C were moved to rooms of 12

and 20°C at 90 – 100% RH, respectively, for eight days in total. For the four control treatments,

fruit were not treated with vibration in different liners (polyethylene and polystyrene) and were kept

at different temperatures (12 and 20°C) for eight days. After eight days of storage, all the fruit were

moved to a ripening room until fruit reached eating ripe. Three blocks (half trays) per treatment and

Figure 6.4 A: Fruit subjected to 3 h of vibration at 12 Hz in polyethylene liners (n = 16); B: Fruit

subjected to 3 h of vibration at 12 Hz in polystyrene liners (n = 16); C: Fruit subjected to 9 h of

vibration at 12 Hz in polyethylene liners (n = 16); D: Fruit subjected to 9 h of vibration at 12 Hz in

polystyrene liners (n = 16); A hard paper board was used to cover each fibreboard tray.

166

eight single fruit replicates per block were used in this experiment. Individual block was taken as

the replicate.

6.2.5 Experiment 3. Effects of vibration duration, storage temperature and tray insert (fruit

grown in the Northern Territory) in the 2013 – 14 and 2014 – 15 seasons

6.2.5.1 Fruit vibrated in two layers in the 2013 – 14 season

‗Honey Gold‘ mango fruit were harvested from a farm near Fox Road in Katherine, Northern

Territory, Australia in December, 2013 following the procedures as described in Section 6.3.1.

The vibration treatments were applied at 12 and 20°C using the vibration table. Due to the

limitation of having only one vibration table, the different temperature treatments were carried out

separately. Vibration treatments at 20°C were conducted firstly and the cold room temperature was

then changed to 12°C. When the cold room temperature reached the set temperature of 12°C after 5

h, and was stable, the 12°C treatments were conducted. The fruit to be treated at 20°C were held for

4 h before treatments to allow them to reach treatment temperature. The fruit to be treated at 12°C

were held in the cold room set at 12°C until their vibration treatment about 24 h later.

Figure 6.5 A, C and F: Fruit treated with 3 h of vibration in polystyrene (left half) and polyethylene

liners (right half) prior to post-treatment quality assessment (n = 8 / block and 3 blocks); B, G and

H: fruit treated with 9 h of vibration in polystyrene (left half) and polyethylene liners (right half)

prior to post-treatment quality assessment (n = 8 / block and 3 blocks); D and E: spare fruit used to

maintain weight balance. An empty fibreboard tray was placed on top of each second layer tray.

167

For each treatment temperature, the fruit were vibrated at 12 Hz for 0, 3, 9 or 18 h (Figure 6.6).

Two layers on the vibration table were used in this experiment. The fruit vibrated for 18 h within

polyethylene and polystyrene liners constituted the first layer, the fruit treated for 3 and 9 h were in

the second layer (Figure 6.6). For consistency in each stack, an empty ‗placebo‘ box covered each

second layer. The 0 h control fruit were held in the same room as the fruit subjected to vibration

treatment. After vibration treatments, the fruit vibrated at 12 and 20°C were moved to the rooms of

12 and 20°C and 90 – 100% RH, respectively, for eight days in total. For the four control treatments,

fruit were not treated by vibration, but were stored in different liners (polyethylene and polystyrene)

at different temperatures (12 and 20°C). After eight days storage, all the fruit were moved to a

ripening room until fruit reached eating ripe. Fifteen individual fruit replicates per treatment were

used in this experiment. Additional one fruit per treatment was used in packing to ensure that fruit

contacted each other tightly.

6.2.5.2 Fruit vibrated in one layer in the 2014 – 15 season

Green mature ‗Honey Gold‘ mango fruit were harvested from a farm near Fox Road, Northern

Territory, Australia in December, 2014 following the procedures as described in Section 6.3.1. The

12°C treatments were initially carried out, followed by the 20°C treatments. For each treatment

Figure 6.6 A and D: Fruit subjected to 18 h of vibration at 12 Hz in polyethylene and polystyrene

liners, respectively (n = 15); E and H: Fruit subjected to 3 h of vibration at 12 Hz in polyethylene

and polystyrene liners, respectively (n = 15); F and G: Fruit subjected to 9 h of vibration at 12 Hz in

polyethylene and polystyrene liners, respectively (n = 15); B and C: Fruit subjected to 18 h of

vibration at 12 Hz in polyethylene liners, respectively, prior to later biochemical analysis (n = 15).

An empty fibreboard tray was placed on top of each second layer tray.

168

temperature, the fruit were vibrated at 12 Hz for 0, 3, 9 or 18 h (Figure 6.7). One single layer on the

vibration table was used in this experiment.

Fruit were placed into each of four trays; two trays with polyethylene liners, and two with

polystyrene liners. Within each tray, half of the fruit were allocated to a 3 h treatment group, while

half were allocated to an 18 h treatment group. After 3 h of vibration at 12 Hz, the fruit from the 3 h

treatment group were removed from each tray. These fruit were replaced with the 9 h treatment fruit.

After a further 9 h of vibration, the 9 h treatment fruit were removed. These fruit were replaced with

spare non-experimental fruit. The remaining fruit were treated by another 6 h of vibration, to result

in a total of 18 h exposure to vibration. After vibration treatments, the fruit vibrated at 12 and 20°C

were moved to rooms of 12 and 20°C at 90 – 100% RH, respectively, for eight days in total. For the

four control treatments, fruit were not treated by vibration, but were stored in different liners

(polyethylene and polystyrene) at different temperatures (12 and 20°C). After eight days of storage,

all the fruit were moved to a ripening room until fruit reached eating ripe. Fourteen individual fruit

replicates were used in this experiment.

Figure 6.7 A and D: Each polyethylene-lined tray contained half 3 h treatment group, half 18 h

treatment group (n = 14). After 3 h of vibration at 12 Hz, half of these fruit were then replaced by

the fruit for 9 h of vibration (n = 14). These treatments were all for later quality assessment. After 9

h of vibration, the removed fruit were replaced with spare non-experimental fruit to maintain tight

fruit contact for finishing the 18 h vibration treatments; B and C: Each polystyrene-lined tray

contained half 3 h treatment group, and half 18 h treatment group (n = 14). After 3 h of vibration at

12 Hz, half of these fruit were then replaced by the fruit for 9 h of vibration (n = 14). These

treatments were all for later quality assessment. After 9 h of vibration treatment, the removed fruit

were replaced with spare non-experimental fruit to maintain tight fruit contact for finishing the 18 h

169

6.2.6 Measurements

USB incidence was the number of fruit affected with USB divided by the total number of fruit and

expressed as a proportion (%). USB severity was expressed as a rating scale and / or area and was

measured using methods as described in Section 5.3.4. Skin colour, firmness and weight loss (%)

were measured as described in Section 3.3.6. PPO, POD activities and total phenolics concentration

were measured as described in Section 4.3.6.


Fruit were vibrated at different temperatures (12 and 20°C) at different times, with a one day delay

between the two temperature treatments. Fruit were vibrated using different liners (polyethylene

and polystyrene) within different trays in all experiments except experiment 2, precluding the

adoption of a completely randomised. In experiment 2, fruit could be supposed to be treated with

completely randomised, but few fruit were affected by USB. Therefore, the results have not been

analysed by statistics. USB incidence was the number of fruit affected with USB divided by the

total number of fruit and expressed as a proportion (%). Other quality parameters including USB

severity (actual area and / or rating scale), skin colour, firmness and weight loss have been

expressed as the mean and standard error of the mean. In addition, biochemistry parameters

including PPO and POD activities, and total phenolics concentration were all expressed as the mean

and standard error of the mean.

6.3 Results

6.3.1 Experiment 1. Effects of fruit growing region, vibration duration, storage temperature

and tray insert in the 2012 – 13 season

Control fruit that were grown in the Northern Territory and North Queensland and kept at 20°C

were unaffected by USB (Table 6.1). No control fruit from the Northern Territory kept at 12°C, and

few grown in Northern Queensland, were affected by USB.

This experiment involved fruit in a single layer of trays of the vibration table. For the polyethylene

liner treatments, fruit from the Northern Territory and North Queensland vibrated for 9 h at 12°C

vibration treatments. An empty fibreboard tray was placed on top of each bottom layer tray.

170

tended to show higher USB incidences than did the control fruit maintained at 12°C. Polystyrene

liner tended to show a lower USB incidence than polyethylene liner for fruit that were vibrated for 9

h grown in any regions. However, similar levels of the incidence of USB were found for control

fruit and the fruit that were vibrated for 3 h.

USB severity was expressed as rating scale and area. USB rating scale was consistent with USB

area. Polyethylene liner tended to show a greater USB area than polystyrene liner for fruit grown in

the Northern Territory. However, similar levels of USB area were found for fruit grown in North

Queensland. Similar levels of USB area were found for fruit vibrated for 3 or 9 h.

171

6.3.2 Experiment 2. Effects of vibration duration, storage temperature and tray insert type

(fruit grown in North Queensland) in the 2013 – 14 season

This experiment involved fruit in two layers on the vibration table. Each fibreboard tray was

divided in half with a paper board in middle, with half of the tray lined with polyethylene liner and

Table 6.1 Effects on USB incidence (%) and severity (rating scale and area [cm2 affected]) of

growing region (Northern Territory and North Queensland), vibration duration at 12 Hz (0, 3 and 9

h) and tray insert (polyethylene and polystyrene) at eating ripe (n = 15). ‗Honey Gold‘ fruit grown

in the Northern Territory and North Queensland collected in the 2012 – 13 season were vibrated for

3 and 9 h in polyethylene and polystyrene liners in a cold room at 12°C and 90 – 100% RH, and

then kept in the same room for eight days in total. Fruit not treated with vibration at 20°C and

others at 12°C for eight days were the two controls. All of them were then moved to the ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data of incidence are expressed as

mean and data of severity are expressed as mean and standard error of the mean.

Treatment USB

Incidence (%) Severity

Rating scale Area (cm2 affected)

Northern Territory

No vibration, 20°C 0 0 0


3h Vibration, polyethylene liner, 12°C 7 4.0 11.53

3h Vibration, polystyrene liner, 12°C 20 2.7 ± 0.9 5.87 ± 4.29

9h Vibration, polyethylene liner, 12°C 60 3.8 ± 0.3 13.54 ± 3.42

9h Vibration, polystyrene liner, 12°C 33 2.4 ± 0.4 4.52 ± 1.56

North Queensland


No vibration, 12°C 7 4.0 16.28


3h Vibration, polystyrene liner, 12°C 7 4.0 15.7


9h Vibration, polystyrene liner, 12°C 0 0 0

172

half of the tray lined with polystyrene liner in this experiment. There was a very low USB incidence

on both vibrated and control fruit grown in North Queensland (Figure 6.8 A and B).

Figure 6.8 A and B: Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3 and 9 h) ,

tray insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 8 /

block and 3 blocks). ‗Honey Gold‘ mango fruit grown in North Queensland collected in the 2013 –

14 season were vibrated for 0 (control), 3 and 9 h at either 12 or 20°C and 90 – 100% RH, and

subsequently kept at 20 or 12°C, respectively, for eight days in total. All the fruit were moved to the

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are expressed as the

mean and standard error of the mean.

6.3.3 Experiment 3. Effects of vibration duration, storage temperature and tray inserts (fruit

grown in the Northern Territory) in the 2013 – 14 and 2014 – 15 seasons

6.3.3.1 Fruit vibrated in two layers in the 2013 – 14 season

Fruit kept at 20°C tended to show a lower USB incidence than did those fruit kept at 12°C (Figure

6.9). USB started to appear on day 2, and did not tend to increase further after day 4 on fruit kept at

20°C (Figure 6.9 A and C). On fruit kept at 12°C, USB started to appear on day 2 and tended to

continue to increase until day 8 or 14 (Figure 6.9 B and D). However, fruit vibrated for 18 h at 20°C

Time from vibration treatments (days)

0 5 10 15 20

US

B i

nci

den

ce (

%)

0

20

40

60

80

100

0 5 10 15 20

US

B i

nci

den

ce (

%)

0

20

40

60

80

100

No vibration (control), polyethylene liner Vibration for 3 h, polyethylene linerVibration for 9 h, polyethylene liner No Vibration (control), polystyrene linerVibration for 3 h, polystyrene liner Vibration for 9 h, polystyrene liner

A B

173

in any liners did not show USB early as compared to the same treatments at12°C as mentioned

above (Figure 6.9 C and D).

This experiment involved fruit in two layers of trays on the vibration table. Fruit were vibrated with

polyethylene and polystyrene liners for 18 h on the first layer (Figure 6.9 C and D), and fruit were

vibrated with polyethylene and polystyrene liners for 3 and 9 h on the second layer (Figure 6.9 A

and B). Fruit on the second layer on the vibration table damaged more than fruit on the first layer

because of a higher acceleration in a higher level (Slaughter et al. 1993, Shahbazi et al. 2010).

Therefore, in this experiment, fruit vibrated for different layers on the vibration table were not

compared together.

For fruit treated in the first layer, those fruit vibrated for 18 h in polyethylene liners tended to show

a higher USB incidence than the control fruit in polyethylene liners at 12°C (Figure 6.9 D). The

polystyrene liner tended to reduce USB incidence on the fruit vibrated for 18 h compared to

polyethylene liner (Figure 6.9 D).

For fruit treated in the second layer, those vibrated for 9 h in polyethylene liners at 20°C tended to

show a higher USB incidence than did their control fruit in polystyrene liners at 20°C (Figure 6.1

A). Fruit vibrated for both 3 and 9 h at 12°C also tended to show higher USB incidences than did

their control fruit (Figure 6.9 B). Compared to the polyethylene liner, the polystyrene liner did not

obviously influence USB incidence at 12°C.

174

Figure 6.9 A and B: Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3 and 9 h), tray

insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 15). C

and D: Effects on USB incidence (%) of vibration duration (0 and 18 h) and tray insert

(polyethylene and polystyrene) at different storage temperature (20 [C] and 12°C [D]) (n = 15).

‗Honey Gold‘ fruit grown in the Northern Territory collected in the 2013 – 14 season were vibrated

for 3 and 9 h in the second layer and for 18 h in the first layer at either 20 (A) or 12°C (B) and 90 –

100% RH, and subsequently kept at either 20 (A) or 12°C (B), respectively, for eight days in total.

As for the four controls treatments, fruit exposed to no vibration in different liners (polyethylene

and polystyrene) were kept at different temperatures (20 and 12°C) for eight days in total. After

eight days storage, all the fruit were moved to a ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe.

A B

C D

A and B C and D

US

B i

nci

den

ce (

%)

0

20

40

60

80

100

No vibration (control), polyethylene linerVibration for 3 h, polyethylene linerVibration for 9 h, polyethylene linerNo vibration (control), polystyrene linerVibration for 3 h, polystyrene linerVibration for 9 h, polystyrene liner

0 5 10 15 20

US

B i

nci

den

ce (

%)

0

20

40

60

80

100

0

20

40

60

80

100


0 5 10 15 20

0

20

40

60

80

100

No vibration (control), polyethylene linerVibration for 18 h, polyethylene linerNo vibration (control), polystyrene linerVibration for 18 h, polystyrene liner

175

The severity of USB symptoms in affected fruit did not appear to differ substantially due to either

vibration duration or liner type (Figure 6.10).

Figure 6.10 A and B: Effects on USB severity (rating scale) of vibration duration at 12 Hz (0, 3 and

9 h), tray insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =

15). C and D: Effects on USB severity (rating scale) of vibration duration (0 and 18 h), and tray

insert (polyethylene and polystyrene) at different storage temperature (20 [C] and 12°C [D]).

‗Honey Gold‘ fruit grown in the Northern Territory collected in the 2013 – 14 season were vibrated

for 3 and 9 h in the second layer and for 18 h in the first layer at either 20 (A) or 12°C (B) and 90 –

100% RH, and subsequently kept at either 20 (A) or 12°C (B), respectively, for eight days in total.

As for the four controls treatments, fruit exposed to no vibration in different liners (polyethylene

0

1

2

3

4

5

No vibration (control), polyethylene linerVibration for 3 h, polyethylene linerVibration for 9 h, polyethylene liner No vibration (control), polystyrene linerVibration for 3 h, polystyrene linerVibration for 9 h, polystyrene liner

0

1

2

3

4

5


0 5 10 15 20

US

B (

0 -

5)

0

1

2

3

4

5

No vibration (control), polyethylene linerVibration for 18 h, polyethylene linerNo vibration (control), polystyrene linerVibration for 18 h, polystyrene liner

A B

C D

A and B C and D

0 5 10 15 20

US

B (

0 -

5)

0

1

2

3

4

5

176

6.3.3.2 Fruit vibrated in one layers in the 2014 – 15 season

USB incidence and severity

This experiment involved fruit in a single layer on the vibration table. When fruit reached eating

ripe, those treated at 12°C tended to show a higher incidence of USB than did those treated at 20 ºC

(Table 6.2). For fruit treated at 20°C, in both polyethylene and polystyrene liners, fruit vibrated for

9 and 18 h tended to show higher incidences of USB than did those vibrated for 3 h and the controls.

However, for fruit treated at 12°C in both polyethylene and polystyrene liners, those vibrated for 3,

9 and 18 h tended to show higher incidences of USB than did the controls. There was no clear

difference in USB incidence between the two different types of liners.

Vibration treatments tended to result in a greater area of USB than did non-vibration treatments at

either 20 or 12°C (Table 6.2). It was observed that USB in fruit vibrated and held at 20°C for eight

days tended to appear lighter in depth of colour than that in fruit treated at 12°C (Figure 6.16).

However, where USB occurred, the severity rating and area did not appear to be strongly affected

by temperature (Table 6.2). There was a tendency for more USB to occur on the ‗shoulder‘ position

as compared to the ‗cheek‘ position of fruit (Table 6.2).

and polystyrene) were kept at different temperatures (20 and 12°C) for eight days in total. After

eight days storage, all the fruit were moved to a ripening room at 20°C and 90 – 100% RH until

fruit reached eating ripe.

177

Table 6.2 Effects of vibration duration at 12 Hz (0, 3 and 9 h), storage temperature (20 and 12°C) and tray insert (polyethylene and polystyrene) on the

incidence (%) and severity (rating scale and area [cm2 affected]) of USB and on the incidence of USB on either ‗cheeks‘ or ‗shoulders‘ positions close

to the stem (n =14) at eating ripe. ‗Honey Gold‘ mango fruit grown in the Northern Territory in the 2014 – 15 season were vibrated for 0 (control), 3, 9

or 18 h in polyethylene or polystyrene liners at 12 or 20°C, and then kept at 12 or 20°C, respectively, for eight days in total. All the fruit were then

moved to a ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Data are expressed as mean and standard error of the mean.

Treatment USB USB

Incidence (%) Severity Incidence (%)

Rating scale Area (cm2 affected) On cheek On shoulder

No vibration (control), polyethylene liner, 20°C 7 1.0 0.5 ± 0 0 7

No vibration (control), polystyrene liner, 20°C 0 0 0 0 0

3 h vibration, polyethylene liner, 20°C 7 3.0 6.5 0 7

3 h vibration, polystyrene liner, 20°C 0 0 0 0 0

9 h vibration, polyethylene liner, 20°C 43 2.3 13.0 ± 7.2 14 36

9 h vibration, polystyrene liner, 20°C 29 3.0 ± 0.7 32.0 ± 15.2 21 21

18 h vibration, polyethylene liner, 20°C 29 3.5 ± 0.5 45.8 ± 12.8 7 29


No vibration (control), polyethylene liner, 12°C 21 3.0 10.3 ± 1.5 0 21

No vibration (control), polystyrene liner, 12°C 14 1.0 3.5 ± 1.5 7 7



178

Table 6.2 (continued)

Treatment USB USB

Incidence (%) Severity Incidence (%)

Rating scale Area (cm2 affected) On cheek On shoulder





179

During ripening, there was a general trend towards the 20°C fruit developing USB more rapidly

(from day 2 to 8) than the 12°C fruit (from day 4 to 17) (Figure 6.11). At 20°C, the vibration

treatments tended to result in a greater severity (rating scale and area) of USB than control

treatments, although this effect was inconsistent at 12°C (Figure 6.12).

Figure 6.11 Effects on USB incidence (%) of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray

insert (polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =14).

‗Honey Gold‘ mango fruit grown in the Northern Territory collected in 2014 – 15 season were

vibrated for 0 (control), 3, 9 and 18 h in polyethylene and polystyrene liners at 12 and 20°C, and

subsequently kept at 12 and 20°C, respectively, for eight days in total. All the fruit were moved to a

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe.


0 5 10 15 20

US

B i

nci

den

ce (

% )

0

20

40

60

80

100

0 5 10 15 20

US

B i

nci

den

ce (

% )

0

20

40

60

80

100

No vibration (control), polyethylene liner

Vibration for 3 h, polyethylene liner

Vibration for 9 h, polyethylene liner

Vibration for 18 h, polyethylene liner No vibration (control), polystyrene linerVibration for 3 h, polystyrene liner Vibration for 9 h, polystyrene liner Vibration for 18 h, polystyrene liner

A B

180

Figure 6.12 Effects on USB rating scale of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =14). ‗Honey

Gold‘ mango fruit grown in the Northern Territory collected in the 2014 – 15 season were vibrated

for 0 (control) or 3 or 9 or 18 h in polyethylene and polystyrene liners at 12 and 20°C, and then kept

at 12 and 20°C, respectively, for eight days in total. All the fruit were moved to a ripening room at

20°C and 90 – 100% RH until fruit reached eating ripe.

0 5 10 15 20

US

B (

0 -

5)

0

1

2

3

4

5

No vibration (control), polyethylene liner Vibration for 3 h, polyethylene liner Vibration for 9 h, polyethylene liner Vibration for 18 h, polyethylene liner No vibration (control), polystyrene linerVibration for 3 h, polystyrene liner Vibration for 9 h, polystyrene liner Vibration for 18 h, polystyrene liner


0 5 10 15 20

US

B (

0 -

5)

0

1

2

3

4

5

A B

181

Quality parameters

Low temperature (12°C) delayed skin colour change, firmness change and weight loss of the fruit

(Figure 6.13, Figure 6.14 and Figure 6.15). Fruit vibrated for a long duration of 18 h had higher

weight loss than did those vibrated for 9 h followed by the 3 h vibration treatment, and control fruit

lost the least weight (Figure 6.15).

Figure 6.13 Effects on skin colour of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n =14). ‗Honey

Gold‘ mango fruit grown in the Northern Territory collected in the 2014 – 15 season were vibrated

for 0 (control) or 3 or 9 or 18 h in polyethylene or polystyrene liners at either 12 or 20°C, and

subsequently kept at either 12 or 20°C, respectively, for eight days in total. All the fruit were moved

to a ripening room at 20°C and 90 – 100% RH until they reached eating ripe.


0 5 10 15 20

Sk

in c

olo

ur

( 1

- 6

)

0

1

2

3

4

5

6

0 5 10 15 20

Sk

in c

olo

ur

( 1

- 6

)

0

1

2

3

4

5

6

A B


182

Figure 6.14 Effects on firmness of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 14). ‗Honey

Gold‘ mango fruit grown in the Northern Territory were vibrated for 0 (control) or 3 or 9 or 18 h in

polyethylene or polystyrene liners at 12 or 20°C, and subsequently kept at 12 or 20°C for eight days

in total. All the fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe.


0 5 10 15 20

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

0 5 10 15 20

Fir

mn

ess

( 0

- 4

)

0

1

2

3

4

A B


183

Figure 6.15 Effects on weight loss of vibration duration at 12 Hz (0, 3, 9 and 18 h), tray insert

(polyethylene and polystyrene) and storage temperature (20 [A] and 12°C [B]) (n = 14). ‗Honey

Gold‘ mango fruit grown in the Northern Territory were vibrated for 0 (control) or 3 or 9 or 18 h in

polyethylene or polystyrene liners at 12 or 20°C, and subsequently kept at 12 or 20°C for eight days

in total. All the fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached

eating ripe.

Biochemistry of the USB response

Similar levels of total phenolics concentration were found in fruit under the various treatments

applied (Table 6.3). However, from day 4 to ripe, fruit vibrated for 18 h at 20°C tended to show

higher PPO and POD activities than did control fruit at 20°C. Nonetheless, fruit vibrated for 18 h at

12°C had similar levels of PPO and POD activity across the sequential assessment times. In the

control and the 18 h vibration treatments, skin affected with USB tended to show lower PPO and

POD activities than did skin with no USB on day 8 but, conversely, tended to show higher activities

at eating ripe.


0 5 10 15 20

Wei

gh

t lo

ss (

% )

0

2

4

6

8

0 5 10 15 20

Wei

gh

t lo

ss (

% )

0

2

4

6

8

A B


184

Table 6.3 Effects on PPO and POD activities (units / mg protein) and total phenolics concentration

(mg GA equivalents / g FW) of vibration for 0 and 18 h at 20 and 12°C in polyethylene and

polystyrene liners in the first layer on a vibration table and then kept at 20 and 12°C, respectively,

for eight days in total (n = 3). ‗Honey Gold‘ fruit grown in the Northern Territory collected in the

2013 – 14 season were vibrated for 18 h at 12 or 20°C and at 90 – 100% RH, and subsequently kept

at 12 or 20°C, respectively, for eight days in total. Fruit exposed to no vibration holding at 20 and

12°C for eight days were the controls. After eight days storage, all fruit were moved to a ripening

room at 20°C and 90 – 100% RH until ripe. Data are expressed as the mean and standard error of

the mean.

Treatment Time from vibration (days)

0 4 8 Eating ripe

PPO activity

No vibration, 20°C (No USB) 61.3 ± 4.9 66.2 ± 4.4 31.5 ± 4.8 0 ± 0

18 h vibration, 20°C (No USB)

99.5 ± 4.9 52.5 ± 12.4 15.3 ± 0.9

No vibration, 12°C (No USB)

66.5 ± 7.2 65.7 ± 6.3 0 ± 0

No vibration, 12°C (USB)

30.3 ± 2.6 37.2 ± 3.2

18 h vibration, 12°C (No USB)

68.2 ± 3.9 60.5 ± 3.3 0 ± 0

18 h vibration, 12°C (USB) 56.4 ± 5.2 54.0 ± 0.4 30.3 ± 1.2

POD activity

No vibration, 20°C (No USB) 28.14 ± 2.19 18.77 ± 1.01 14.31 ± 1.53 11.34 ± 0.77

18 h vibration, 20°C (No USB) 56.45 ± 1.03 33.15 ± 2.03 16.56 ± 0.33

No vibration, 12°C (No USB) 26.26 ± 3.17 27.91 ± 2.01 13.86 ± 0.77

No vibration, 12°C (USB) 15.15 ± 0.29 20.32 ± 2.09


18 h vibration, 12°C (USB) 19.29 ± 0.91 17.24 ± 0.40 18.12 ± 1.40

Total phenolics concentration

No vibration, 20°C (No USB) 15.29 ± 0.28 12.37 ± 0.33 19.72 ± 0.75 26.77 ± 0.69


No vibration, 12°C (No USB) 19.31 ± 0.28 23.24 ± 1.33 22.52 ± 0.76

No vibration, 12°C (USB) 26.25 ± 1.20 24.9 ± 0.28


18 h vibration, 12°C (USB) 21.02 ± 0.31 23.68 ± 0.84 22.68 ± 0.01

185

Figure 6.16 Images of ‗light‘ USB in ‗Honey Gold‘ fruit treated with 18 h vibration in a

polystyrene liner at 20°C (A), and of ‗dark‘ USB in fruit treated with 9 h vibration in a

polyethylene liner at 12°C (B).

6.4 Discussion

Relatively long durations (9 and 18 h) of vibration tended to increase USB incidence for ‗Honey

Gold‘ from Northern Territory. Lower storage temperatures tended to increase USB incidence, with

fruit vibrated and stored at 12°C tending to show higher incidences of USB than at 20°C. These

results confirmed the hypothesis that USB can be triggered by physical stress and intensified by low

temperature. Control (non-vibrated) fruit at 20°C were typically unaffected by USB. However, the

USB response was observed in non-vibrated fruit at 12°C, typically at low levels of incidence. It is

theorised that the USB occurring in non-vibrated fruit may have been triggered by incidental

physical stress, such as vibration during transportation from the Northern Territory to Brisbane after

harvest.

Polystyrene liners did not consistently reduce USB as compared to polyethylene liners. Liners with

greater cushioning can reduce mechanical damage by increasing the surface area of contact with the

fruit, thereby spreading the load over a greater area (Sitkei, 1986). However, the polystyrene liners

used in these experiments were of a low profile, which would reduce the impact of fruit contact on

the bottom of fibreboard trays but would not reduce fruit-to-fruit or fruit-to-tray side contact

efficiently. The higher, but harder polyethylene liners may have restricted fruit movement more

through their higher profile, but would not have provided the cushioning benefits of polystyrene.

These conflicting properties are possibly the reason for the inconsistent effects of the two liner

types on USB.

A B

186

Fruit from North Queensland subjected to vibration within fibreboard trays had a markedly higher

susceptibility to USB incidence in the 2012 – 13 mango season (Table 6.1) than the fruit from

North Queensland subjected to vibration within each fibreboard tray divided with a paper board in

middle in the 2013 – 14 mango season (Figure 6.8). This difference may have resulted solely from

seasonal variation, but the change in packing arrangement may also have influenced USB incidence.

It is possible that fruit may have been more restricted in their movement by the central divider in the

tray, or that fruit-to-fruit contact points were reduced. The harvest season has been reported to

influence the occurrence of browning in citrus fruit (Montero et al., 2012) and fruit-to fruit contact

was proposed by Marques et al. (2012) to be one cause inducing USB.

Compared to storage at 20°C, low temperature of 12°C delayed changes in skin colour, firmness

and weight loss (Figure 6.13, Figure 6.14 and Figure 6.15) in ‗Honey Gold‘ mango fruit. Effect of

low temperature on delaying skin colour and firmness changes have been reported on other tropical

fruits, including loquat fruit (Ding et al., 1998) and ‗Tommy Atkins‘ and ‗Keitt‘ mango fruit

(Medlicott et al., 1990).

Vibration did not influence skin colour and firmness changes but did influence weight loss. Longer

durations of vibration, resulted in greater resultant weight loss from the fruit (Figure 6.15).

Mechanical damage often damages the barriers to moisture loss on the fruit surface, such as the

cuticle and epicuticular waxes, reducing the ability of the fruit to resist moisture loss (Serrano et al.,

2004).

Higher PPO activity was found in USB-affected areas of the fruit skin as compared with non-USB-

affected areas at eating ripe, for fruit stored at either 12 or 20°C. However, the increase in PPO

activity was not found during the development of USB in skin tissue on less ripe fruit on days 4 and

8. Overall, PPO, POD activities and total phenolics concentration seem less possible to be closely

associated with USB expression.

USB symptoms were visibly different from the symptoms of physical damage on mango fruit.

Therefore, it is suggested that the underlying mechanism of USB is not solely the disruption of

epidermal and sub-epidermal cell integrity, and that other factors are potentially involved. It is

possible that USB instead results from damage by toxic compounds of sap leakage from resin ducts

beneath the epidermal cells layer under physical stress (Loveys et al., 1992, Bezuidenhout, 2005,

Marques et al., 2012), which will be studied further in Chapter 7. Peel pitting of ‗Encore‘ mandarin

(Shomer, 1980, Bosabalidis and Tsekos, 1982, Medeira et al., 1999) and tangerine (Jarimopas et al.,

187

2005) fruit have been similarly associated with the release of gland oil underneath the epidermal

cells. Robinson et al. (1993) reported that sapburn on mango skin is predominantly catalysed by

PPO in the skin not the PPO in the sap. Therefore, it is a possibility that toxic compounds of sap

from resin ducts leaked to surrounding cells after physical stress (abrasion and vibration) damaged

cell membrane (Knobloch et al., 1989), caused phenolics contact to PPO in the skin tissue and

finally resulted in USB on ‗Honey Gold‘ mango fruit. This also could explain why PPO activity in

skin tissue was found not closely correlated to USB. In addition, a higher incidence of USB occurs

on the ‗shoulder‘ (the position nearby the stem) than the ‗cheek‘ of fruit, especially on vibrated fruit

(Table 6.2). This may suggest that USB is related to the sap remaining inside the mango fruit and

moving towards and expressing more from the stem end of the fruit.

In addition, it was observed that USB was lighter in colour on fruit vibrated at 20°C but darker in

colour on fruit vibrated at 12°C (Figure 6.16). It was not evident why low temperature intensified

the darkened colour of USB. A higher incidence of USB occurred on vibrated and abraded fruit

exposure to 12°C than at 20°C. This may be related to the effect of low temperature on cell integrity

and membrane (Lyons et al., 1979). So far there has been few evidence supporting on it yet, which

will be studied in Chapter 7.

6.5 Conclusion

In simulated transportation, vibration involving fruit-to-fruit contact was likely one of main factors

inducing USB, with low temperature intensifying USB symptom expression. This proposition as

supported by the results herein substantiates that vibration and low temperatures (≤ 12°C) during

transport are the key causes of USB on ‗Honey Gold‘ mango fruit. Reduced physical stress during

transport and temperature control should effectively reduce USB. Trialing the packaging of

individual mango fruit in polystyrene foam nets or designing a packing box with cardboard divider

in combination with the use of nets would be worth investigation. PPO and POD activities and total

phenolics concentration are evidently not closely correlated with USB symptom expression. The

sap left in resin ducts which could be influenced by physical stress and low temperature is possibly

involved in the mechanism of USB expression. Therefore, characterising the anatomy of USB and

effects of mango sap on fruit is important to understand USB and may provide supports for the

hypothesis (Chapter 7). In addition, studies on genetics for USB on ‗Honey Gold‘ is worth trying,

which will help understand the mechanism of this disorder.

188

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technology: damage to loquats by vibration-simulating intra-state transport. Biosystems

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Bosabalidis, A. and Tsekos, I. 1982. Ultrastructural studies on the secretory cavities of Citrus

deliciosa ten. II. Development of the essential oil-accumulating central space of the gland

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Ding, C.-K., Chachin, K., Hamauzu, Y., Ueda, Y. and Imahori, Y. 1998. Effects of storage

temperatures on physiology and quality of loquat fruit. Postharvest Biology and


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Jarimopas, B., Singh, S. P. and Saengnil, W. 2005. Measurement and analysis of truck transport

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329-333.

Ketsa, S. and Atantee, S. 1998. Phenolics, lignin, peroxidase activity and increased firmness of

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Knobloch, K., Pauli, A., Iberl, B., Weigand, H. and Weis, N. 1989. Antibacterial and antifungal

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Medeira, M., Maia, M. and Vitor, R. 1999. The first stages of pre-harvest ‗peel pitting‘

development in ‗Encore‘ mandarin. An histological and ultrastructural study. Annals of

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Medlicott, A., Sigrist, J. and Sy, O. 1990. Ripening of mangos following low-temperature storage.

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Olorunda, A. and Tung, M. 1985. Simulated transit studies on tomatoes; effects of compressive

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Quintana, M. E. G. and Paull, R. E. 1993. Mechanical injury during postharvest handling of ‗Solo‘

papaya fruit. Journal of the American Society for Horticultural Science, 118: 618-622.



Saltveit, M. E. 2000. Wound induced changes in phenolic metabolism and tissue browning are

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191

The Role of Mango Sap in Under-skin Browning Chapter 7

Abstract

Under-skin browning (USB) occurs in the sub-epidermal cells of ‗Honey Gold‘ mango skin tissue.

This physiological disorder may be associated with the sap release from resin ducts beneath the

epidermis. Sap sample (viz., time of sap collection [morning and afternoon], sap type [spurt and

ooze] and upper-phase spurt sap) in combinations with storage temperature (viz., 12 and 20°C)

were investigated as to their effects on skin browning for fruit treated by different damage types

(viz., abraded, cutting and peeled epidermis). Two sets of controls were maintained; a positive

control, in which fruit were treated with distilled water, and a negative control in which fruit were

treated with terpinolene. The latter is a known mango sap component. Upon these treatments the

anatomy of three associated disorders (USB, mild and severe skin browning) were characterised

towards understanding USB. The incidence and severity of mild, severe and total (sum of mild and

severe) skin browning symptoms were measured. At anatomical levels, typical USB and the severe

browning damaged by terpinolene and spurt sap mainly showed green and dark tinged browning.

The browning in green colour was found in the USB on skin tissue, and in the severe skin browning

on skin tissue caused by synthesised terpinolene and spurt sap is similar. Therefore, terpinolene in

spurt sap evidently contributed to the greenish browning. However, the dark browning was also

observed in USB and in the severe browning caused by spurt sap not in the severe browning caused

by terpinolene. It was suggested that other compounds in spurt sap may be typically involved in

occurrence of USB. The low temperature of 12°C consistently increased the incidence of mild,

severe and total skin browning as compared to 20°C. It is consistent with a higher incidence of USB

on vibrated or abraded ‗Honey Gold‘ mango fruit at 12°C compared to at 20°C. It was concluded

that exposure fruit to a low temperature of 12°C can intensify USB as compared to fruit held at

20°C.

Keywords: ‗Honey Gold‘ mango fruit, damage type, low temperature, sap, skin browning,

terpinolene

7.1 Introduction

Mango (Mangifera indica L.) fruit and stems have extensive systems of resin ducts (laticifers), as is

common in the Anacardiaceae family (Joel et al., 1978, Joel, 1981). These systems synthesise and /

or store resinous secretions. The laticifers of mango fruit and stems are not interconnected as both

192

terminate in the fruit abscission zone (Joel, 1981). Sap or latex in fruit laticifers is maintained under

high turgor pressure whilst the fruit are connected to the peduncle. This high turgor pressure is

attributed to a large amount of non-dialyzable and non-starchy carbohydrate in the sap (Joel, 1980).

When the stem is removed during harvest, sap spurts initially and later exudes slowly from the stem

scar and can damage (‗burn‘) the fruit surface (Loveys et al., 1992). Sapburn is a common skin

browning disorder on commercially harvested mango fruit.

Mango sap typically separates into a yellow-brown oily upper-phase and a milky liquid lower-phase

(Loveys et al., 1992). In ‗Kensington Pride‘ mango fruit, terpinolene was abundant in the upper-

phase sap fraction, which has been suggested to be associated with skin browning (Loveys et al.,

1992). Treatment of ‗Kensington Pride‘ fruit skin with synthesized terpinolene at > 1%

concentration caused skin browning (Loveys et al., 1992). Robinson et al (1993) suggested that skin

browning induced by sapburn was predominantly catalysed by polyphenol oxidase in the skin and

not in the sap per se.

De-stemming mango fruit in a solution of 1% calcium hydroxide (O'Hare and Prasad, 1991) or 1%

aluminium potassium sulphate (Brown et al., 1986) can reduce sapburn injury. Commercial de-

sapping formulations such as Mango Wash® (Septone, Illinois Tool Works Inc., QLD, Australia)

are commonly used to reduce the risk of sapburn.

Cultural practices and environmental conditions may affect the incidence and severity of sapburn,

most likely through influencing sap characteristics. For example, sap collected from ‗Samra Bahisht

Chaunsa‘ mango fruit in the afternoon caused more severe damage when applied to the fruit skin

than did sap collected in the morning (Maqbool, 2007). Fruit of this cultivar harvested in the

afternoon were more affected by sapburn than those harvested in the morning (Amin et al., 2008).

Under-skin browning (USB) is manifested as a brown-grey bruise-like lesion underneath the

epidermis (Marques et al., 2012). It predominantly affects the ‗Honey Gold‘ cultivar. Its expression

is related to physical stress, such as vibration, and exposure to low temperature (Chapter 6). USB

incidence was also observed to be higher on the ‗shoulder‘ position than on the ‗cheek‘ position of

mango fruit (Chapter 6), which might be associated with more sap accumulation and / or flow close

to the stem. It is hypothesised that USB may be induced by sap escaping from resin ducts under the

skin of ‗Honey Gold‘ mango fruit. In this context, sap samples (the collection time, sap type and

upper-phase spurt sap), storage temperature and physical damage type were investigated to

understand their potential relationship to the incidence and severity of browning disorders (mild,

193

severe and total browning [sum of mild and severe browning]). Severe and mild skin browning

symptoms as caused by sap and terpinolene and also typical USB were also characterised

anatomically.


7.2.1 Materials

7.2.1.1 Mango fruit

Green mature ‗Honey Gold‘ mango fruit (dry matter content = 18.9%) were grown under standard

commercial conditions at an orchard near Fox Road in Katherine, Northern Territory, Australia

(14.46ºS; 132.24ºE) in December, 2013 and 2014. Fruit harvested at 8 am were de-stemmed and de-

sapped in a solution of Mango Wash®

(Septone, ITW AAMTech, NSW, Australia). They were

taken to a nearby packinghouse and treated and packed under standard commercial conditions,

including fungicide treatment (Sportak®, a.i. prochloraz, Bayer Crop Science, VIC, Australia),

brushing, drying and sorting (Hofman et al., 2010). All fruit were graded for uniform quality and

size and packed into single layer fibreboard trays with polystyrene liners and two layers of bubble

wrap on top of the fruit to prevent compression injury during transportation. The fruit were

transported by car to Darwin, Northern Territory, Australia within 3 h. They were then air-freighted

from Darwin to Brisbane, Queensland, Australia (27º49‘S, 153º03‘E). The fruit were finally

transported by car to a postharvest lab in the Ecosciences Precinct. They arrived within 48 h of

harvest. The fruit were assigned to treatments in a completely random fashion in preparation for

treatment.

7.2.1.2 Mango sap

Green mature ‗Honey Gold‘ mango fruit were harvested in the morning at 8 am and in the afternoon

at 2 pm from commercially managed trees grown at an orchard near Fox Road as described in

Section 7.2.1.1. Fruit were collected with 5 cm of stem attached and carefully placed into plastic

crates. The fruit were immediately transported by car to a nearby packing house where their sap was

collected. Spurt sap was collected in the first 60 s after detaching stem. Ooze sap was collected

from then on. Spurt sap was directed down a metal channel (Figure 7.1) into a collection bottle.

Ooze sap was collected directly into another collection bottle. After sap collection was completed,

two layers of aluminium foil were placed over the bottle openings and plastic screw caps were

194

secured in place. The foil was used to avoid compounds in sap being absorbed by the cap. Sap

samples were kept on dry ice (-78ºC, BOC, NT, Australia) in an insulated foam container. They

were then air-freighted from the Northern Territory to Brisbane as described in Section 7.2.1.1.

Figure 7.1 Image of the device used to collect spurt and ooze sap from ‗Honey Gold‘ mango fruit.

7.2.2 Abrasion, cutting and peeling preparation treatments

In the laboratory, the surfaces of mango fruit to be treated were prepared for application of sap

samples. Three approaches were adopted: (1) Abrasion – Section 5.2.2. The abrasion area was ~ 0.8

– 2 cm2. (2) Cut – ~ 0.5 cm-wide, ~ 1 cm-long and ~ 0.3 cm-deep fruit skin blocks were removed

with a scalpel blade. (3) Peeling – ~ 2 – 4 cm2 of fruit skin was removed with a vegetable peeler.

7.2.3 Sap centrifugation

The frozen sap from dry ice was thawed at 4ºC and shaken thoroughly in preparation for

centrifugation. Spurt, morning and afternoon sap of sap samples were separated into lower and

upper fractions according to Loveys et al. (1992) with minor modification. Briefly, 10 ml each of

morning and afternoon spurt sap in glass tubes were centrifuged at 3,000 rpm for 5 min at room

temperature (~ 26°C). Then, 5 ml each of upper-phase morning and upper-phase afternoon spurt sap

in total were collected for treatments as described in Section 7.2.4.

195

7.2.4 Experiment 1. Effects of sap sample, storage temperature and damage type

7.2.4.1 2013 – 14 season

Each fruit was abraded, cut or peeled at four positions. A 0.1 ml sample of morning and afternoon

spurt sap, upper-phase morning spurt sap, upper-phase afternoon spurt sap, morning and afternoon

ooze sap was then placed onto abraded, cut and peeled skin treatment positions using a glass

syringe. Distilled water (0.1 ml, ‗negative control‘) and terpinolene (0.05 ml, ‗positive control‘,

Sigma-Aldrich Inc., MO, USA) were also applied to abraded, cut and peeled skin, respectively. A

rectangular piece of filter paper ~ 1 cm2 was then secured in place to retain the liquid droplets on

the treated fruit area. A sheet of aluminium foil (~ 35 cm2) with plastic tape was placed over the

treatment zone to reduce sap vaporisation. Fruit were then held at either 12 or 20°C and 90 – 100%

RH for eight days, when upon the foil and filter paper patches were removed. The fruit were then

maintained in a ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Three

individual fruit replicates each comprised of four positions (sub-samples) per treatment were used

in this experiment. Because only limited volume of morning spurt sap and afternoon ooze sap were

collected, upper-phase morning spurt sap, and morning and afternoon ooze sap treatment were not

applied on peeled skin treatment positions.

7.2.4.2 2014 – 15 season

The general procedures in Section 6.3.1 were repeated for abraded skin treatment of fruit harvested

in the 2014 – 15 season. Aliquots (0.1 ml) of morning spurt sap, afternoon spurt sap, upper-phase

morning spurt sap, upper-phase afternoon spurt sap were then placed onto abraded skin positions

with a glass syringe as described in Section 7.2.4.1. Distilled water (0.1 ml) and terpinolene (0.1 ml,

Sigma-Aldrich Inc., MO, USA) were the negative and positive controls, respectively. Three

individual fruit replicates each comprised of four positions (sub-samples) per treatment were used

for the morning spurt sap, afternoon spurt sap, distilled water and terpinolene treatments. However,

three individual fruit replicates each comprising one position (sub-sample) per treatment were used

for the upper-phase morning spurt sap and upper-phase afternoon spurt sap treatments because of

limited volume of sap collected.

196

7.2.5 Experiment 2. Effects of storage temperature and terpinolene

This experiment investigated the effects of terpinolene volume and storage temperature on skin

browning. Fruit were abraded (Section 7.3.2) and different volumes of terpinolene (100, 50, 25,

12.5, 6.3 and 3.1 μl) were used. Fruit treated with 0.1 ml distilled water were the controls. The fruit

were held at either 12 or 20°C and 90 – 100% RH for eight days. All fruit were then maintained in a

ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Three individual fruit

replicates each comprising of four positions (sub-samples) each fruit per treatment were used in this

experiment.

7.2.6 Anatomy

These methods are described in Section 4.3.5.

7.2.7 Measurements

Green to dark sunken browning on treated fruit were characterised as severe skin browning and

grey non-sunken browning were rated as mild skin browning (Figure 7.2). Total skin browning was

the sum of the severe skin browning and mild skin browning. The severity (cm2 affected) of mild,

severe and total skin browning symptoms were measured using Image J software (National Institute

of Mental Health, Maryland, USA, http://imagej.nih.gov/ij/ ) (Section 5.2.9.2). The incidence of

mild, severe and total skin browning symptoms for each individual fruit replicate was calculated by

the number affected divided by the sub-samples number of four.


Completely randomised designs were used for all experiments and statistical analyses were

conducted using GenStat (2013). The incidence data on mild, severe and total skin browning were

subjected to an unbalanced generalised linear model under the binomial distribution and logit link

(McCullagh and Nelder, 1989) by different factors in two experiments. In experiment 1 in the 2013

– 14 season, the factors were damage type (viz., abraded, cut and peeled), sap sample (viz., morning

and afternoon spurt sap, upper-phase morning and afternoon spurt sap, terpinolene and afternoon

ooze sap) and temperature (viz., 12 and 20ºC). Distilled water and morning ooze sap were not

involved in statistical analyses because they did not cause any damage on fruit in any of the

experiments. In experiment 1 in the 2014 – 15 season, the factors were sap sample (viz., terpinolene,

http://imagej.nih.gov/ij/

197

morning spurt sap, afternoon spurt sap, upper-phase morning spurt sap and upper-phase afternoon

spurt sap) and temperature (viz., 12 and 20ºC). In experiment 2, the factors were terpinolene volume

(viz., 100, 50, 25, 12.5, 6.3 and 3.1 μl) and temperature (viz. 12 and 20ºC) in analyses on mild and

total skin browning severity. The factors were terpinolene volume (viz. 100, 50, 25 and 12.5 μl) and

temperature viz. (12 and 20ºC) in analyses of severe skin browning severity. Terpinolene at 6.3 and

3.1 μl did not cause any severe browning and was not incorporated in statistical analyses on severity.

Conditional (unbalanced or balanced) ANOVA was used for analysing mild, severe and total skin

browning severity by the same factors as mentioned above in different experiments. The

significance of differences between treatments was determined using the protected Fisher test at the

5% level.

7.3 Results

Mild to severe skin browning resulted from topical administration of afternoon mango spurt sap to

damage zones on ‗Honey Gold‘ mango fruit (Figure 7.2 A). The severe skin browning symptoms

were greenish in colour, sunken in profile and leathery to touch. The colour of this severe skin

browning was darker than that of severe skin browning caused by the application of terpinolene

(Figure 7.2 C). Mild skin browning symptoms were yellow-brown in colour without a sunken

profile (Figure 7.2 A). Similar symptoms resulted from application of afternoon spurt sap, upper-

phase spurt morning and afternoon sap fractions. Typical USB symptoms resulting from vibration

stress were grey-brown in colour (Figure 7.2 B). The application of terpinolene caused a large area

of severe skin browning and a small area of mild skin browning on fruit (Figure 7.2 C).

198

Figure 7.2 Images of symptoms caused by afternoon spurt sap topically applied at a mechanically

damaged site to a ‗Honey Gold‘ mango fruit (A), typical USB symptoms on a ‗Honey Gold‘ mango

fruit treated with 12 Hz of vibration for 9 h in soft polystyrene liner (Chapter 6) (B) and symptoms

of terpinolene damage on a ‗Honey Gold‘ mango fruit (C). SB: Severe skin browning; MB: mild

skin browning; USB: under-skin browning.

7.3.1 Anatomy of tissue affected with USB, severe skin browning, mild skin browning and no

browning

Compared to the anatomy of skin tissues with no USB (Figure 7.3 A), the positions of the skin

tissues with USB, the severe browning caused by terpinolene and spurt sap, and mild skin browning

caused by spurt sap in skin tissue cells were different (Figure 7.3 C, E, G and I). USB occurred in

sub-epidermal cells surrounding the resin ducts beneath the epidermis in distinct bands (Figure 7.3

C). The severe browning caused by terpinolene (Figure 7.3 E) and spurt sap (Figure 7.3 G) occurred

in the sub-epidermis and epidermis. Mild browning caused by spurt sap occurred in the epidermis

(Figure 7.3 I).

199

Under light microscopy, the greenish browning was observed in USB-affected skin tissue and in the

skin tissue affected with the severe browning caused by terpinolene and spurt sap but not in the skin

tissue with mild browning (Figure 7.3 D, F, H and I). In addition, the dark browning was found in

tissue affected with USB and in tissue affected with the severe browning caused by spurt sap but

not in the severe browning caused by terpinolene (Figure 7.3 D, F and H).

No visible differences was found on non-stained and toluidine blue stained tissue affected with USB,

or severe or mild skin browning, or no browning (Figure A 4.1).

200

Figure 7.3 Transverse unstained hand sections through ‗Honey Gold‘ mango fruit skin samples

treated with 12°C as affected with no USB (control; A [× 4], B [× 10]), with USB (C [× 4], D [×

10]), with severe skin browning due to terpinolene application (E [× 4], F [× 10]), with severe skin

browning due to spurt sap application (G [× 4], H [× 10]) and with mild skin browning spurt sap

application (I [× 4], J [× 10]). Bars 100 μm (A, C, E, G and I) and 50 μm (B, D, F, H and J). Ep:

epidermal cells; Sp: sub-epidermal cells; RD: resin duct;GB: greenish browning; DBL dark

browning; MB: mild skin browning.

A B

C D

F E

201

Figure 7.3 (continued)

7.3.2 Experiment 1. Effects of sap sample, storage temperature and damage type

7.3.2.1 2013 – 14 season

Application of distilled water (0.1 ml) and morning ooze sap (0.1 ml) to ‗Honey Gold‘ fruit did not

cause any of mild, severe or total skin browning at any storage temperature (12 and 20°C).

Therefore, they were not included in the statistical analyses. Afternoon ooze sap, morning spurt sap,

afternoon spurt sap, upper-phase morning spurt sap, upper-phase afternoon spurt sap and

terpinolene in this experiment defined as sap sample which was taken as one factor involved in

statistical analyses.

G H

J I

202

Severe skin browning

Two significant (P < 0.05) interactions were found for severe skin browning incidence. These were

a significant (P = 0.029) interaction of storage temperature and damage type and a significant (P =

0.002) interaction of sap sample and damage type (Table 7.1). In the significant (P = 0.029)

interaction of storage temperature and damage type, fruit kept at 12°C developed a higher incidence

of severe skin browning than did fruit kept at 20°C for any damage type, although the effects in

abrasion were not significant (P = 0.05). In the significant (P = 0.002) interaction of sap sample and

damage type, fruit treated with afternoon spurt sap had a significantly (P < 0.05) higher incidence

of severe damage than did fruit treated with morning spurt sap for any damage type. The treatment

of fruit with 0.05 ml terpinolene caused a 100% incidence of severe skin browning. Fruit treated

with upper-phase morning spurt sap and upper-phase afternoon spurt sap had a higher incidence of

severe skin browning than did fruit treated with morning spurt sap and afternoon spurt sap,

respectively, for any damage type, although the difference between afternoon spurt sap and its

upper-phase in abrasion way was not significant (P = 0.05).

203

Table 7.1 Two significant interactions of storage temperature and damage type, and of sap sample

and damage type on severe skin browning incidence (%) (n = 3 individual fruit replicates

comprising 4 sub-samples per fruit). ‗Honey Gold‘ mango fruit were harvested from Northern

Territory in the 2013 – 14 season. Different sap sample of 100 µl aliquots of morning and

afternoon spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and 100 µl of distilled water

was applied to small areas of the fruit abraded with sand paper or peeled with peeler or cut with a

scalpel blade. The fruit were then held in either 12 or 20°C room at 90 – 100% RH for eight days

and all fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached eating

ripe. Data for incidence are expressed as mean and those followed by the same letters are not

signficant.

Factors Severe skin browning incidence (%)

Storage temperature × damage type

Abraded Cut Peeled

20°C 59 ab 54 a 75 c

12°C 68 bc 76 c 92 d

Sap sample × damage type

Abraded Cut Peeled

Terpinolene 100 e 100 e 100 e

Morning spurt sap 0 a 21 b 0 a

Afternoon spurt sap 77 cd 54 c 54 c

Afternoon ooze sap 0 a 25 b -

Upper-phase of morning spurt sap 88 de 63 c -

Upper-phase of afternoon spurt sap 88 de 100 e 96 de

Unbalanced generalised linear model under the binomial distribution and logit link

Damage type ***

Storage temperature **

Sap sample ***

Damage type × storage temperature **

Damage type × sap sample ***

Storage temperature × sap sample NS

Damage type × storage temperature × sap sample NS

*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant (P

< 0.001); NS: not significant; ‗-‘: no treatment applied

204

Two significant (P < 0.05) interactions were found for severe skin browning severity (cm2

affected).

These were a significant (P = 0.044) interaction of sap sample and damage type and a significant (P

= 0.030) interaction of sap sample and storage temperature (Table 7.2). In a significant (P = 0.044)

interaction of sap sample and damage type, fruit treated with terpinolene developed the highest

severity of skin browning among all the treatments. Fruit treated with upper-phase morning and

afternoon spurt sap had a higher severity of skin browning than did fruit treated with morning and

afternoon spurt sap, respectively, for any damage type; although the difference between upper-

phase afternoon spurt sap and afternoon spurt sap was not significant (P = 0.05). The treatment of

fruit with upper-phase morning and afternoon spurt sap significantly (P < 0.05) caused a higher

severity of skin browning than morning and afternoon spurt sap, respectively. In the significant (P =

0.030) interaction of sap sample and storage temperature, fruit response for different temperatures

was different depending upon sap sample on severe skin browning severity. The difference between

severe skin browning on fruit caused by terpinolene stored at 12 and 20°C was significant (P <

0.05). However, the differences of severe skin browning on fruit caused by sap samples stored at 12

and 20°C were not significant (P = 0.05).

205

Table 7.2 Two significant interactions of sap sample and storage temperature, and of sap sample

and damage type on severe skin browning severity (cm2 affected) (n = 3 individual fruit replicates

comprising 4 sub-samples per fruit). ‗Honey Gold‘ fruit were harvested from Northern Territory in

the 2013 – 14 season. Different sap sample of 100 µl aliquots of morning and afternoon spurt sap,

100 µl of their upper-phase, 50 µl of terpinolene and 100 µl of distilled water was applied to small

areas of the fruit abraded with sand paper or peeled with peeler or cut with a scalpel blade. The fruit

were then held in either 12 or 20°C room at 90 – 100% RH for eight days and all fruit were moved

to a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for severity are

expressed as mean and the significant difference between the treatments when the difference of

them is ≥ the data of LSD.

Factors Severe skin browning severity (cm2 affected)

Sap sample × storage temperature

12°C 20°C

Terpinolene 10.9 7.85

Mo ning spurt sap 1.16 0

Afternoon spurt sap 2.60 1.19

Afternoon ooze sap 1.58 0

Upper-phase of morning spurt sap 4.79 4.06

Upper-phase of afternoon spurt sap 5.82 6.32

LSD = 2.04


Abraded Cut Peeled

Terpinolene 10.54 10.17 7.51

Morning spurt sap 0 1.16 0

Afternoon spurt sap 2.14 1.69 2.24

Afternoon ooze sap 0 1.58 -

Upper-phase of morning spurt sap 4.25 4.67 -

Upper-phase of afternoon spurt sap 4.46 6.99 6.65

LSD = 2.07

Conditional ANOVA

Damage type 0.533

Storage temperature 0.703

Sap sample < 0.001

Damage type × storage temperature 0.286

206

Mild skin browning

The temperature at which fruit were stored was found to significantly (P < 0.001) influence the

incidence of mild skin browning (Table 7.3). Fruit kept at 12°C developed a significantly (P < 0.05)

higher incidence of mild skin browning than did fruit kept at 20°C. A significant (P = 0.013)

interaction of sap sample and damage type was found for mild skin browning incidence (Table 7.3).

Treatment with afternoon spurt sap resulted in a significantly (P < 0.05) higher incidence of mild

skin browning than morning spurt sap for fruit that were peeled and cut prior to sap application.

While there appeared to be a trend for a slight increase in skin browning on fruit treated with

afternoon spurt sap over morning spurt sap, there was no significant (P = 0.05) treatment effect.

Damage type × Sap sample 0.041

Storage temperature × Sap sample 0.030

Damage type × storage temperature × Sap sample 0.142


0.001); NS: not significant; ‗-‘: no treatment applied.

207



A significant (P = 0.003) interaction of damage type and sap sample was found for the severity of

mild skin browning (Table 7.4). Sap type response for damage way was different on mild skin

Table 7.3 Significant effect of storage temperature and a significant interaction of sap sample and

damage type on mild skin browning incidence (%) (n = 3 individual fruit replicates comprising 4

sub-samples per fruit). ‗Honey Gold‘ mango fruit were harvested from the Northern Territory in the

2013 – 14 season. Different sap sample of 100 µl aliquots of morning and afternoon spurt sap, 100

µl of their upper-phase, 50 µl of terpinolene and 100 µl of distilled water was applied to small areas

of the fruit abraded with sand paper or peeled with peeler or cut with a scalpel blade. The fruit were

then held in either 12 or 20°C at 90 – 100% RH for eight days and all fruit were moved to a

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for incidence are

expressed as mean and those followed by the same letters are not significant.

Factors Mild skin browning incidence (%)

Storage temperature

20°C 12°C

64 a 84 b


Abraded Cut Peeled

Terpinolene 88 de 83 de 75 cde

Morning spurt sap 75 cde 33 b 42 b

Afternoon spurt sap 96 e 92 e 96 e

Afternoon ooze sap 0 a 46 bc -

Upper-phase of morning spurt sap 96 e 63 bcd -

Upper-phase of afternoon spurt sap 96 e 92 e 88 de


Damage type NS

Storage temperature ***

Sap sample ***

Damage type × storage temperature NS

Damage type × sap sample *



208

browning severity. There was no significant (P < 0.05) effect of sap sample on the mild browning

response in abraded fruit. However, cut fruit treated with upper-phase morning spurt sap developed

higher severity of mild browning than morning spurt sap in cut fruit, and afternoon spurt sap and its

upper-phase had significantly (P < 0.05) higher severity of the browning than those treated with

morning spurt sap and terpinolene.

Table 7.4 A significant interaction of damage type and sap sample on mild skin browning severity

(cm2

affected) (n = 3 individual fruit replicates comprising 4 sub-samples per fruit). ‗Honey Gold‘

fruit were harvested from Northern Territory in the 2013 – 14 season. Different sap sample of 100

µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl of terpinolene and

100 µl of distilled water was applied to small areas of the fruit abraded with sand paper or peeled

with peeler or cut with a scalpel blade. The fruit were then held in either 12 or 20°C at 90 – 100%

RH for eight days and all fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit

reached eating ripe. Data for severity are expressed as mean and the significant difference between

the treatments when the difference of them is ≥ the data of LSD.

Factors Mild skin browning severity (cm2

affected)

Damage type × Sap sample

Abraded Cut Peeled

Terpinolene 1.77 1.55 1.52

Morning spurt sap 2.00 1.67 1.90

Afternoon spurt sap 2.59 2.18 4.74

Afternoon ooze sa 0 1 52 -

Uppe -phase of morning spurt sap 2.53 3.05 -

Upper-phase of afternoon spurt sap 2.47 2.98 3.97

LSD = 0.94

Damage type ***

Storage temperature NS

Sap sample ***


Damage type × sap sample **



209



Total skin browning

Storage temperature was also found to significantly (P < 0.001) influence total skin browning

incidence (Table 7.5). When averaged across all treatments, fruit kept at 12°C developed

significantly (P < 0.05) a higher incidence of total skin browning than did fruit kept at 20°C. A

significant (P = 0.013) interaction of damage type and sap sample was found for total skin

browning incidence (Table 7.5). Fruit treated with afternoon spurt sap had a significantly (P < 0.05)

higher incidence of total skin browning than fruit treated with morning spurt sap for any damage

type. Fruit treated with upper-phase morning spurt sap had a significantly (P < 0.05) higher

incidence of total skin browning than did fruit treated with morning spurt sap. However, the

response to afternoon ooze sap was significantly (P < 0.05) different between fruit that were either

abraded or cut.

210

Table 7.5 Effect of storage temperature and a significant interaction of sap sample and damage

type on total skin browning incidence (%) (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ fruit were harvested from Northern Territory in the 2013 – 14

season. Different sap sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of

their upper-phase, 50 µl of terpinolene and 100 µl of distilled water was applied to small areas

of the fruit abraded with sand paper or peeled with peeler or cut with a scalpel blade. The fruit

were then held in either 12 or 20°C at 90 – 100% RH for eight days and all fruit were moved to

a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for incidence

are expressed as mean and those followed by the same letters are not significant.

Factors Total skin browning incidence (%)

Temperature

20°C 73 a

12°C 85 b


Abraded Cut Peeled

Terpinolene 96 f 100 f 100 f

Morning spurt sap 75 de 33 b 42 bc

Afternoon spurt sap 96 f 92 ef 96 f

Afternoon ooze sap 0 a 46 bc -

Upper-phase of morning spurt sap 96 f 63 cd -

Upper-phase of afternoon spurt sap 100 f 100 f 100 f


Damage type NS

Storage temperature **

Sap sample ***


Damage type × sap sample ***



*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant

(P < 0.001); NS: not significant; ‗-‘: no treatment applied.

211

A significant (P < 0.001) interaction of storage temperature, damage type and sap sample was found

for the severity of total skin browning (Table 7.6). As for the treatments at 20°C, fruit applied with

upper-phase morning spurt sap and upper-phase afternoon spurt sap significantly (P < 0.05)

developed greater severity of total skin browning than did fruit applied with upper-phase morning

spurt sap and upper-phase afternoon spurt sap for any damage type. As for the treatments at 12°C,

fruit applied with upper-phase morning spurt sap and upper-phase afternoon spurt sap developed

higher severity of total skin browning than did morning spurt sap and afternoon spurt sap for fruit

that were abraded, peeled and cut prior to sap application, although the effects of afternoon spurt

sap for abrading and peeling experiments were not significant (P = 0.05).

212

Table 7.6 A significant interaction of sap sample, damage type and storage temperature on total

skin browning severity (cm2 affected) (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ fruit were harvested from the Northern Territory in the 2013 –

14 season. Different sap sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of

their upper-phase, 50 µl of terpinolene and 100 µl of distilled water were applied to small areas

of the fruit abraded with sand paper or peeled with peeler or cut with a scalpel blade. The fruit

were then held in either 12 or 20oC at 90 – 100% RH for eight days and all fruit were moved to

a ripening room at 20oC and 90 – 100% RH until fruit reached eating ripe. Data for severity are

expressed as mean and the significant difference between the treatments when the difference of

them is ≥ the data of LSD.

Total skin browning severity (cm

2

affected)

Sap sample × damage type × storage temperature Abraded Cut Peeled

Terpinolene, 20ºC 8.58 9.34 7.24

Morning spurt sap, 20ºC 1.95 1.99 0.91

Afternoon spurt sap, 20ºC 2.78 3.13 6.29

Afternoon ooze sap, 20ºC 0 1.48 -

Upper-phase of morning spurt sap, 20ºC 6.16 4.35 -

Upper-phase of afternoon spurt sap, 20ºC 9.81 6.98 9.60

Terpinolene, 12ºC 13.52 10.19 7.34

Morning spurt sap, 12ºC 2.81 2.36 2.88

Afternoon spurt sap, 12ºC 5.30 2.41 5.77

Afternoon ooze sap, 12ºC 0 2.51 -

Upper-phase of morning spurt sap, 12ºC 6.36 8.61 -

Upper-phase of afternoon spurt sap, 12ºC 6.13 11.89 8.65

LSD = 3.21

Conditional ANOVA

Damage type 0.708

213

Storage temperature 0.082

Sap sample < 0.001

Damage type × storage temperature 0.197

Damage type × sap sample 0.002

Storage temperature × sap sample 0.648

Damage type × storage temperature × sap sample 0.001

*: statistically significant (P < 0.05); **: 0.001 < P < 0.01; ***: statistically highly significant

(P < 0.001); NS: not significant, ‗-‘: no treatment applied.

7.3.2.2 2014 – 15 season

Fruit treated with distilled water did not develop browning. Accordingly, they were not included in

statistical analyses. Morning spurt sap, afternoon spurt sap, upper-phase morning spurt sap, upper-

phase afternoon spurt sap and terpinolene in this experiment defined as sap sample which was taken

as one factor involved in statistical analyses.


The sap sample was found to significantly (P < 0.001) influence the incidence of severe skin

browning (Table 7.7). Treatment with terpinolene and upper-phase afternoon spurt sap caused 100%

severe skin browning. Application of upper-phase morning spurt sap caused a significantly (P <

0.05) lower incidence of severe skin browning (50%). Morning and afternoon spurt sap treatments

did not cause any severe skin browning.

The sap sample was found to significantly (P < 0.001) influence severe skin browning severity

(Table 7.8). Treatment of fruit with terpinolene resulted in significantly (P < 0.05) higher severity

of browning than exposure to upper-phase morning spurt sap and upper-phase afternoon spurt sap.

Mild skin browning

Storage temperature and sap sample were found to significantly (P < 0.001) influence mild skin

browning incidence (Table 7.7). Fruit kept at 12°C resulted in a significantly (P < 0.001) higher

214

incidence than fruit kept at 20°C. Fruit treated with upper-phase morning and afternoon spurt sap

developed higher incidences than fruit treated with morning and afternoon spurt sap.

Sap sample was found to significantly (P < 0.001) influence mild skin browning severity (Table

7.8). Treatment of fruit with the upper-phase fraction of afternoon spurt sap resulted in a

significantly (P < 0.05) higher mild skin browning severity than upper-phase of morning spurt sap,

morning and afternoon spurt sap. Storage temperature was found to significantly (P = 0.049)

influence mild skin browning severity. Fruit kept at 12°C had significantly (P < 0.05) higher

severity than fruit kept at 20°C.

Total skin browning

Storage temperature and sap sample were found to significantly (P < 0.001) influence total skin

browning incidence (Table 7.7). Fruit kept at 12ºC had a significantly (P < 0.05) higher incidence

than did fruit kept at 20ºC. Fruit treated with terpinolene had a significantly (P < 0.05) higher

incidence than did fruit treated with morning and afternoon spurt sap.

Sap sample was found to significantly (P < 0.001) influence total skin browning area (Table 7.8).

Fruit treated with terpinolene had the highest severity of total skin browning among all the sap

samples. Fruit treated with upper-phase afternoon spurt sap had significantly higher severity than

upper-phase morning spurt sap, morning and afternoon spurt sap. Fruit treated with upper-phase

afternoon spurt sap had significantly (P < 0.05) higher severity of total skin browning than fruit

treated with afternoon spurt sap, morning spurt sap and its upper-phase.

215



Table 7.7 Effects of storage temperature on incidence (%) of mild, severe and total skin browning

of abraded fruit (n = 3 individual fruit replicates comprising 4 sub-samples per fruit for morning

and afternoon spurt sap, terpinolene; n = 3 individual fruit replicates comprising 1 sub-sample per

fruit for upper-phase morning and afternoon spurt sap). The fruit were harvested from Northern

Territory in the 2014 – 15 season. Different sap sample of 100 µl aliquots of morning and afternoon

spurt sap, 100 µl of their upper-phase and 50 µl of terpinolene were applied to small areas of the

fruit abraded with sand paper or peeled with peeler or cut with a scalpel blade. The fruit were then

held in either 12 or 20°C at 90 – 100% RH for eight days and all fruit were moved to a ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data for incidence are expressed as

mean and those followed by the same letters are not significant.

Factors Incidence (%)

Severe skin

browning

Mild skin

browning

Total skin

browning

Storage temperature

20°C 26 a 43 a

12°C 64 b 76 b

Sap sample

Terpinolene 100 c 50 b 100 c

Morning spurt sap 0 a 25 a 25 a

Afternoon spurt sap 0 a 33 ab 33 b

Upper-phase morning spurt sap 50 b 100 c 100 c

Upper-phase afternoon spurt

sap 100 c 100 c 100 c


Storage temperature NS *** ***

Sap sample *** *** ***

Storage temperature × sap

sample NS NS NS

216



Table 7.8 Effects on total, severe and mild skin browning severity (cm2 affected) on abraded fruit

treated with different sap sample and kept at 12 or 20°C (n = 3 individual fruit replicates comprising

4 sub-samples per fruit for morning and afternoon spurt sap, terpinolene; n = 3 individual fruit

replicates comprising 1 sub-sample per fruit for upper-phase morning and afternoon spurt sap).

‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2014 – 15 season.

Different sap sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-

phase and 50 µl of terpinolene were applied to small areas of the fruit abraded with sand paper or

peeled with peeler or cut with a scalpel blade. The fruit were then held in either 12 or 20°C at 90 –

100% RH for eight days and all fruit were moved to a ripening room at 20°C and 90 – 100% RH

until fruit reached eating ripe. Data for incidence are expressed as mean which calculated by the

number affected with severe skin browning divided by total number. Data for severity are expressed

as mean and those followed by the same letters are not significant.

Factors Severity (cm2 affected)

Severe skin

browning

Mild skin

browning

Total skin

browning

Storage temperature

20°C 3.32 a

12°C 4.17 b

Sap samples

Terpinolene 3.57 b 25.63 c 23.51 b

Morning spurt sap 1.58 a 1.58 a 0

Afternoon spurt sap 1.82 a 1.82 a 0

Upper-phase morning spurt sap 2.24 a 3.45 a 5.32 a

Upper-phase afternoon spurt

sap

7.36 c 12.81 b 1.80 a

Conditional unbalanced ANOVA

Storage temperature * NS NS

Sap sample *** ** ***

Storage temperature × sap

sample

NS NS NS

217

7.3.3 Experiment 2. Effects of temperature and volumes of terpinolene

The volume of terpinolene applied to fruit was found to significantly (P < 0.001; P < 0.001; P <

0.001) influence the incidence of mild, severe and total skin browning (Table 7.9). Terpinolene of ≤

6.3 μl did not cause any severe browning. However, application of 3.1 – 100 μl terpinolene caused

mild browning. Since total browning is the sum of mild and severe browning, application of 1 – 100

μl terpinolene caused total browning. Treatment with 12.5 μl of terpinolene resulted in a

significantly (P < 0.05) lower incidence of severe browning than other higher volumes (25, 50 and

100 μl). Fruit treated with 3.1 μl of terpinolene had a significantly (P < 0.05) lower incidence of

mild browning and total browning than those treated with ≥ 12.5 μl of terpinolene.

218

The volume of terpinolene was found to significantly (P < 0.001; P < 0.001; P < 0.001) influence

the severity of mild, severe and total browning (Table 7.10). The severity of severe browning

increased progressively with increasing volumes of terpinolene over the range of 12.5 – 100 μl. The

severity of mild browning increased with increasing volumes (3.1 – 12.5 μl) and then decreased

thereafter with increasing volume (12.5 – 100 μl). The severity of total browning increased with

increasing volumes (3.1 – 12.5 μl).

Table 7.9 Effect on the incidence (%) of the abraded position treated with different volumes of

terpinolene kept at 12 and 20°C (n = 3 individual fruit replicates comprising 4 sub-samples per

fruit). ‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2013 – 14 season.

Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl terpinolene) were applied to

small areas of the fruit that were abraded with sand paper or peeled with peeler or cutted with

scalpel. All fruit were then kept in different rooms (12 and 20°C) at 90 – 100% RH for eight days

and all fruit were moved to a ripening room at 20°C and 90 – 100% RH until fruit reached eating

ripe. Data of incidence were expressed as mean which calculated by the number affected with mild

skin browning divided by total number. Data of severity are expressed as mean and those followed

by the same letters are not significant.

Factors Incidence (%)

Severe skin

browning

Mild skin

browning

Total skin

browning

Volume of terpinolene (μl)

100 100 b 100 b 100 b

50 100 b 100 b 100 b

25 92 b 100 b 100 b

12.5 58 a 100 b 100 b

6.3 0na

79 a 79 a

3.1 0na

75 a 75 a

G neralize l ner model with binomial regression with logit link

Storage temperature NS NS NS

Volume *** *** ***

Storage temperature × volume NS NS NS


0.001); na: not statistical analyses; NS: not significant.

219

7.4 Discussion

Upon topical application of mango spurt sap onto mechanically damaged fruit skin, ‗Honey Gold‘

skin tissue progressively developed mild and / or severe skin browning before day 8 from moving

Table 7.10 Effect on the severity (cm2 affected) of the abraded position treated with different

volumes of terpinolene kept at 12 and 20°C (n = 3 individual fruit replicates comprising 4 sub-

samples per fruit). ‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2013 –

14 season. Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl terpinolene, and

distilled water) were applied to small areas of the fruit that were abraded with sand paper or peeled

with peeler or cutted with scalpel. All fruit were then kept in different rooms (12 and 20°C) at 90 –

100% RH for eight days and all fruit were moved to a ripening room at 20°C and 90 – 100% RH

until fruit reached eating ripe. Data of incidence were expressed as mean which calculated by the

number affected with mild skin browning divided by total number. Data of severity are expressed as

mean and those followed by the same letters are not significant.

Factors Severity (cm2 affected)

Severe skin

browning

Mild skin

browning

Total skin

browning

Volume of terpinolene (μl)

100 16.91 c 3.14 b 18.71 e

50 7.75 b 3.12 b 10.99 d

25 2.31 a 3.91 bc 6.21 c

12.5 0.43 a 4.68 c 5.00 bc

6.3 0 3.44 b 3.44 ab

3.1 0 8 a 1.98 a

Storage temperature

12°C 8.00 b

20°C 7.36 a

Conditional ANOVA

Storage temperature NS NS NS

Volume *** *** ***

Storage temperature × volume NS NS NS



220

them (day 0) to a ripening room set at 20°C and 90 – 100% RH. The severity and incidence of these

browning disorders did not increase after day 8. These symptoms were similar to typical USB

expression such as begins at day 4 and ends at day 8 and does not increase after day 8 under

ripening conditions (Chapter 5 and 6).

At the tissue level, symptoms of USB were visibly concentrated largely around resin canals in

distinct bands parallel to the surface within sub-epidermal cell layers (Figure 7.3 C). On the other

hand, severe skin browning as induced by topical application of mango spurt sap and terpinolene

was manifested as intense browning in epidermal and sub-epidermal cells (Figure 7.3 E and G). The

reason for the difference in symptomology might be a function of the topical application of the

terpinolene and the spurt sap. These compounds permeated inwards from the mechanically

damaged surface towards the flesh. In contrast, natural USB is most likely induced by sap release

from resin ducts underneath the mango skin (Marques et al., 2012). Leakage of essential oil from

citrus rind glands to surrounding cells had been reported be possibly related to peel pitting on

‗Encore‘ mandarin (Medeira et al., 1999).

At anatomical levels, the severe browning caused by terpinolene and spurt sap showed high

similarity as typical USB. Green tinged browning was observed in skin tissue with typical USB and

the skin tissue with the severe skin browning caused by terpinolene and spurt sap applications

(Figure 7.3 D, F and H). It is suggested that terpinolene in mango spurt sap may induce green tinged

browning on fruit for USB. Dark tinged browning was also observed in skin tissue with USB and

the skin tissue with the severe skin browning caused by spurt sap browning, but not in the severe

browning caused by terpinlene (Figure 7.3 D, F and H). Other compounds, such as car-3-ene, in

spurt sap might be more involved in dark tinged browning in USB (Loveys et al., 1992). In

conclusion, the severe browning by spurt sap seems similar to typical USB except the affected

positions in skin tissue are different (Figure D and H).

The skin browning responses of ‗Honey Gold‘ fruit varied according to sap type (ooze and spurt),

the time of day (morning and afternoon) and upper-phase spurt sap. Ooze sap caused markedly less

incidence and severity of severe browning than spurt sap in experiments 1 and 2. Afternoon spurt

sap caused a markedly higher incidence of severe browning than morning spurt sap. Similarly,

Maqbool et al. (2007) reported that the treatment of ‗Samar Bahisht Chaunsa‘ mango fruit with

spurt sap collected in the afternoon caused more sapburn injury than did the spurt sap collected in

the morning. One possibility is that terpinolene is present at a higher concentration in afternoon sap

than in morning sap (Maqbool, 2007), which will be quantified using gas chromatography-mass

221

spectrometer (GC-MS) to support this hypothesis. It could be influenced by the increased tree sap

flow in the afternoon and fruit temperature (Singh et al., pers. comm., 2015). Upper-phase afternoon

spurt sap and upper-phase morning spurt sap caused higher incidences and severity of severe skin

browning than afternoon spurt sap and morning spurt sap, respectively. After centrifugation, a

higher proportion of upper-phase sap was observed in the afternoon spurt sap than in morning spurt

sap itself. Terpinolene has been found to be mainly in the upper phase (Loveys et al., 1992). These

observations confirmed that terpinolene and other compounds in the upper-phase spurt sap

contributes mainly to severe skin browning, by damaging cell membranes (Knobloch et al., 1989)

and then causing PPO contact with phenolics resulting in enzymatic browning. These findings are

consistent with commercial observations that a higher incidence of USB occurs in fruit harvested in

the afternoon than in the morning (G. Scurr, pers. comm., 2015).

There was marked difference on the severe browning caused by application of spurt sap in the 2013

– 14 and 2014 – 15 seasons. In citrus, seasonal influence have been reported on the occurrence of

oleocellosis (Montero et al., 2012). Variations in environmental conditions and / or management

practices may account for the different responses between the 2013 – 14 and 2014 – 15 seasons.

Exposure to low temperature of 12°C consistently increased the incidence of mild skin browning

and total skin browning in both mango fruiting seasons. In addition, the low temperature of 12°C

increased the incidence of severe skin browning when topical applications of morning and

afternoon spurt sap could cause severe skin browning. These findings are consistent with higher

incidence of USB in abraded or vibrated fruit at 12 than 20°C as reported in Chapters 5 and 6.

7.5 Conclusion

From anatomical observations of the symptoms, browning associated with USB occurs in sub-

epidermal cells surrounding resin ducts beneath the ‗Honey Gold‘ mango fruit skin. From

observations and topical treatments of fruit with mango fruit sap fractions and terpinolene, USB is

likely induced by sap leakage from resin canals under mango skin. The greenish brown

discolouration observed on fruit displaying USB was similar to the green tinge browning seen on

fruit with severe skin browning caused by topical treatments with terpinolene and with spurt sap.

Natural terpinolene in sap is suggested to be a key causal factor in USB, particularly that expressing

with greenish colour. The dark browning symptoms were found in USB-affected skin tissue and the

skin tissue affected with severe skin browning caused by spurt sap but not in the skin tissue affected

with severe skin browning caused by terpinolene. It is possible that other compounds in spurt sap

222

are also involved in modulating the shades and intensity of discolouration associated with USB.

When compared to a temperature of 20°C, exposure to the low temperature of 12°C markedly

increased the incidence of mild, severe and total browning caused by spurt sap. In order to make

this hypothesis being more convinced, the composition of sap collected at different times (morning

and afternoon) such as terpinolene and car-3-ene from ‗Honey Gold‘ mango fruit and other mango

cultivars should be studied. The biochemical analysis of sap from ‗Honey Gold‘ mango fruit is also

worth investigating.

References

Alférez, F. and Zacarias, L. 2000. Postharvest pitting in navel oranges at non-chilling temperature:

influence of relative humidity. Acta Horticulturae, 553: 307-308.

Amin, M. 2008. Mango fruit desapping in relation to time of harvesting. Pakistan Journal of

Botany, 40: 1587-1593.

Assimakopoulou, A., Tsougrianis, C., Elena, K., Fasseas, C. and Karabourniotis, G. 2009. Pre-

harvest rind-spotting in ‗Clementine‘ mandarin. Journal of Plant Nutrition, 32: 1486-1497.

Brown, B., Wells, I. and Murray, C. 1986. Factors affecting the incidence and severity of mango

sapburn and its control. ASEAN Food Journal, 2: 127-132.

Chikaizumi, S. 2000. Mechanisms of rind-oil spot development in ‗Encore‘ (Citrus nobilis Lour.×

C. deliciosa Ten.) fruit. Journal of the Japanese Society for Horticultural Science, 69: 149-

155.

GenStat. 2013. GenStat for Window, Release 15.3. VSN International Ltd, Helmel Hempstead, UK.

Joel, D. 1980. Resin ducts in the mango fruit: a defence system. Journal of Experimental Botany, 31:

1707-1718.

Joel, D. 1981. The duct systems of the base and stalk of the mango fruit. Botanical Gazette, 142:

329-333.

Joel, D. M., Marbach, I. and Mayer, A. M. 1978. Laccase in anacardiaceae. Phytochemistry, 17:

796-797.








223


Pakistan journal of botany, 39: 1565-1574.




McCullagh, P. and Nelder, J. A. 1989. Generalized linear models (2nd

). Chapman and Hall, New

York, USA.



Botany, 83: 667-673.




O'Hare, T. and Prasad, A. 1991. The alleviation of sap-induced mango skin injury by calcium

hydroxide. Frontier in Tropical Fruit Research, 321: 372-381.



224

General Discussion and Conclusion Chapter 8

Mango is a popular tropical fruit around the World. In Australia, ‗B74‘ and ‗Honey Gold‘ cultivars

have been commercialized and contribute ~ 20% and ~ 4% of total mango production, respectively

(AMIA, 2014).

Lenticel discolouration (LD) and under-skin browning (USB) are cosmetic problems on ‗B74‘ and

‗Honey Gold‘ mango fruit, respectively (Hofman et al., 2009). LD is evident as red through brown

to black ‗halos‘ surrounding lenticels. ‗B74‘ is a highly susceptible cultivar to LD as compared to

some other cultivars, including ‗Honey Gold‘, ‗Kensington Pride‘ and ‗R2E2‘ (Joyce et al., 2010).

Under-skin browning (USB) is a typical disorder of ‗Honey Gold‘ mango fruit. It is evident as

browning in sub-epidermal cells (Marques et al., 2012).

8.1 Part A. LD on ‘B74’ Mango Fruit

Lenticels are macroscopic pores in plant tissues that regulate gas exchange (Kader and Saltveit,

2003). Water and air entry into lenticels (Tamjinda et al., 1992), postharvest handling activities

such as hot water (Jacobi et al., 2001) and disinfectants treatments (Bally et al., 1996), low

temperature exposure (Pesis et al., 2000) and fruit sap exposure (Loveys et al., 1992) can increase

LD on mango fruit. γ-Irradiation is a phytosanitary treatment commonly used on harvested mango

fruit that markedly increases LD. To date, no ameliorative postharvest treatments have been

reported for reducing LD manifested on mango fruit after γ-irradiation. In addition, few reports on

biochemistry of LD have been published (Joyce et al., 2011).

8.1.1 Postharvest treatments reduce LD

Drying of orchard soil was considered to make fruit less susceptible to LD by decreasing the

amount of latex and fruit skin and pulp moisture contents in line with reduced tree water potentials

(Cronje, 2009). Fruit bagging in paper around and on top of fruit reduced LD on ‗Tommy Atkins‘

and ‗Keitt‘ mango fruit (Cronje, 2009). The presence of weaver ants (Oecophylla smaragdine) and

potassium treatments have also been ascertained to decrease LD incidence (Peng and Christian,

2005). Harvesting and picking methods that involve fruit being harvested in the morning and fruit

picked with the stem end facting down, prevented LD induced by mango sap (Cronje, 2009). Hot

water treatment was also found to reduce red LD on mango fruit (Joyce et al., 2001, Simão de Assis

et al., 2009). Storage conditions in bulk bins at picking time influenced LD. In this regard, storing

225

‗Tommy Atkins‘ and ‗Keitt‘ mango fruit at low fruit and air temperature and at high humidity

lessened LD (Cronje, 2009).

There has been little work on LD after irradiation. In the present work (Chapter 3), postharvest

chemical treatments with putative anti-browning chemicals (viz., ascorbic acid, citric acid, calcium

ascorbate and calcium chloride) failed to reduce LD expression on ‗B74‘ mango fruit induced by γ-

irradiation (Figure 8.1). These results were in contrast with the effects of anti-browning chemicals

in reducing browning on, for example, fresh-cut apple fruit (Gil et al., 1998, Fan et al., 2005).

Similarly in terms of a lack of positive effect, carnauba waxing postharvest at different

concentrations (viz., 10, 20, 40, 75 and 80%) did not reduce LD. Treatment with three layers of 75%

carnauba wax did not reduced LD induced by γ-irradiation (Figure 8.1). However, the fruit failed to

ripen due evidently to excessively modified internal atmospheres (Baldwin, 2010, Amarante and

Banks, 2001). Macro-perforated bags and paper bags, high humidity inside macro-perforated bags

and nitrogen in polyethylene bags also did not reduce LD. Maintaining fruit inside polyethylene

bags reduced LD on fruit (Figure 8.1). However, LD increased after the day fruit were removed

from the bags. Moreover, this bagging treatment caused some fruit to fail to ripen. Similar effects of

modified atmosphere packaging in reducing skin browning by lowering oxygen concentration have

been reported on litchi (Sivakumar and Korsten, 2006) and banana (Nguyen et al., 2004) fruit. Fruit

ripeness stage was a treatment variable that markedly influenced the severity of LD on ‗B74‘

mango fruit. Sprung fruit showed less of an increase in LD than did hard and rubbery ripening stage

fruits over the first five days after γ-irradiation. By the time fruit reached eating ripe, the sprung

fruit that expressed reduced LD. By the time fruit reached eating ripe, the sprung fruit that

expressed reduced LD were without any negative effects on skin colour, titratable acidity and

soluble solids concentration (Figure 8.1). Therefore, γ-irradiation of ‗B74‘ mango fruit at a more

advanced ripeness stage is an effective approach to reduce LD.

8.1.2 Mechanism of LD on fruit after γ-irradiation

In the present work, the effect of polyethylene bagging treatment on LD indicates that enzymatic

browning processes are involved which are presumably inhibited by low oxygen (Chapter 3). It

confirmed that LD induced by γ-irradiation could be an enzymatic browning process (Figure 8.1).

Total phenolics concentration in irradiated mango skin tissue was not correlated to the expression of

LD. However, polyphenol oxidase (PPO) activity was evidently involved and peroxidase (POD)

activity was possibly involved (Figure 8.1).γ-Irradiated mango fruit skin showed elevated PPO

activity that peaked on day 5. In association with lower PPO activity, LD increased less over the

226

first five days in the skin of sprung irradiated fruit than it did in the skin of hard and rubbery, and

irradiated fruit. A correlation between PPO activity and skin browning has been reported for

irradiated banana fruit (Thomas and Nair, 1997). Higher POD activity was found in irradiated fruit

than in non-irradiated fruit from day 8. In potato, high POD activity was found in irradiation-

induced tuber browning (Ogawa and Uritani, 1970). In bagging treatment experiments, transient

positive polyethylene bagging effects in reducing LD were likely attributable to lowered (i.e.

limiting) oxygen concentrations as opposed to any effects mediated by PPO and POD activities and

/ or total phenolics concentration (Sivakumar and Korsten, 2006, Nguyen et al., 2004).

Figure 8.1 A schematic model on the effects on lenticel discolouration of postharvest treatments

(chemicals [anti-browning agents], bagging, waxing and fruit ripeness) prior to γ-irradiation and the

mechanism of lenticel discolouration induced by γ-irradiation. The red arrow means ‗did not

influence‘. The black arrow means ‗is related with‘.

8.2 Part B. USB on ‘Honey Gold’ Mango Fruit

USB on ‗Honey Gold‘ mango fruit is typically found after commercial consignments are road-

freighted from the Northern Territory and North Queensland to metropolitan markets in southern

Australia, a 3-day road journey (Hofman et al., 2009). Accumulation of starch granules is evident

under light microscopy in USB-affected tissue (Marques et al., 2012). Abrasion has been used a test

for inducing USB on fruit (Hofman et al., 2009). Road transportation at 12 – 14°C increased the

227

incidence of USB as compared to no road transportation under 12 – 14°C (Marques et al., 2012).

Delays of one day at 27 – 35°C before packing plus two days at 18 – 20°C after packing before

moving fruit to 12 – 14°C, reduced the incidence of USB as compared to moving fruit to 12 – 14°C

within 13 h after picking and road transportation (Marques et al., 2012). Otherwise, there is a little

information in regard to the mechanism and cause/s of USB on ‗Honey Gold‘ mango fruit.

8.2.1 Postharvest treatments effects on USB

The incidence and severity are the two parameters for USB expression. Fruit growing region, low

storage temperature, and physical stress by abrasion and simulated vibration tests, were

deterministically related to USB incidence. However, USB severity was found to be closely related

to the abrasion test and low storage temperature.

8.2.1.1 Fruit growing region

Under abrasion treatments, fruit grown in the tropical region (Northern Territory) were more

susceptible to USB than were fruit grown in the sub-tropical region (North Queensland), while fruit

grown in Southeast Queensland had no USB (Chapter 5, Figure 8.2). Similar reports on variance in

browning have been reported in the contexts of watercore in ‗Fuji‘ apple fruit (Harker et al., 1999)

and internal browning in ‗Conference‘ pear fruit (Franck et al., 2007).

8.2.1.2 Physical stress

Exposure to fruit grown in the Northern Territory and North Queensland to the abrasion test caused

higher total USB incidence than for non-abraded fruit (Chapter 5, Figure 8.2). Moreover, abrasion

tended to induce a higher severity of USB surrounding the abrasion position than for USB away

from the abrasion site. Vibration consistently caused a higher total USB incidence than did non-

vibration on ‗Honey Gold‘ mango fruit (Chapter 6, Figure 8.2). Fruit without abrasion at 12°C had

few USB, but the fruit treated with abrasion had a high incidence of USB. In addition, fruit with

abrasion stored at 16°C was affected with a high incidence of USB. Therefore, physical stress (viz.,

abrasion and vibration) was closely related to USB incidence on this mango cultivar (Figure 8.2).

Physical stresses of vibration and abrasion after harvest have been reported to cause browning on

other fruits as well as mango in association with damage to epidermal and sub-epidermal cells

(Kader, 1989). In addition, the duration of vibration is related to the incidence of USB in that the 18

h vibration treatments caused a higher incidence than did the vibration treatments.

228

8.2.1.3 Low storage temperature

In abrasion treatments, low storage temperature was linked to the incidence of USB away from the

immediate abrasion position (i.e. EUSB) and of USB surrounding the abrasion position (i.e. AUSB)

(Chapter 5). The responses of EUSB and AUSB to low temperature were different. Exposure to ≤

10°C caused higher EUSB incidences than did treatments at > 10°C. However, a higher incidence

of AUSB was observed at ≤ 16°C than at 20°C. The effect of low temperature at 12°C on

intensifying the incidence of USB was confirmed in vibration treatments (Chapter 6, Figure 8.2).

Moreover, low storage temperature was correlated to the severity of AUSB surrounding the

abrasion position (Chapter 5). Exposure to the temperatures of 10 and 16°C caused the highest

severity of AUSB among all the temperature treatments, including 6, 7, 8, 12, 13 and 20°C. Since

AUSB contributed predominantly to TUSB (total under-skin browning sum of EUSB and AUSB),

the same effects on TUSB were found. Therefore, low storage temperature was found to be closely

related to USB incidence and severity.

8.2.1.4 Other factors

As compared to fruit treated in the polyethylene liners, fruit treated in the polystyrene liner did not

consistently decrease USB incidence (Chapter 6, Figure 8.2). Liners with greater cushioning can

reduce mechanical damage by increasing the surface area of contact with the fruit, thereby

spreading the load over a greater area (Sitkei, 1986). However, the polystyrene liners used in these

experiments were of a low profile, which would reduce the impact of fruit contract on the bottom of

fibreboard trays but would not reduce fruit-to-fruit or fruit-to-tray side contact efficiently. The

higher, but harder polyethylene liners may have restricted fruit movement more through their higher

profile, but would not have provided the cushioning benefits of polystyrene. These conflicting

properties may be the reason for the inconsistent effects of the two liner types on USB incidence.

‗Honey Gold‘ fruit from the same region of North Queensland showed significantly different

susceptibility to USB development in response to vibration treatments in the 2012 – 13 and 2013 –

14 seasons (Chapter 6). This difference may have resulted solely from seasonal variation. A

seasonal influence on the occurrence of oleocellosis has been found for citrus fruit (Montero et al.,

2012). In addition, the change in fruit packing arrangement within trays between the two seasons

may also have influenced USB incidence. It is possible that fruit may have been more restricted in

their movement by the central divider used in the trays during the 2013 – 14 season, and that fruit-

229

to-fruit contact points were reduced. Differences in fruit-to fruit contact, one important factor

contributing USB, was also proposed by Marques et al. (2012).

Storage duration at 13°C was related to USB severity (Chapter 5). The USB severity increased in

response to increasing storage duration at 13°C. Delaying fruit abrasion to day 4 as compared to

fruit abrasion test impositions on days 0 and 1 reduced the severity of USB, but not the incidence of

USB (Chapter 5). ‗Honey Gold‘ fruit size was not associated with increased or decreased incidence

and severity of USB (Chapter 5). Delaying fruit cooling and the abrasion test imposition did not

influence the incidence and severity of USB (Chapter 5).

8.2.2 Mechanism of USB on fruit

Low temperatures at ≤ 10°C caused USB without differences in USB severity (Chapter 5). Fruit

from the most tropical region were more affected in terms of the incidence of USB. However, no

differences in skin chlorophyll fluorescence (Fv / Fm) ratios, an established parameter for chilly

injury, as assessed after the day of abrasion treatment were found among temperature treatments. In

addition, USB on either vibrated or abraded fruit generally began to express on fruit in a cold room

at 12°C and 90 – 100% RH on day 4 and the incidence and severity increased from then on to day 8

(Chapter 5). The severity and incidence did not markedly change when the fruit were moved on day

8 to a ripening room at 20°C and 90 – 100% RH. In contextual contrast, chilling injury per se on

fruits and vegetables typically increases upon their being moved to ambient conditions (Paull, 1990).

The reported chilling temperature range for mango fruit is ~ 12 – 13°C (Phakawatmongkol et al.,

2004). However, USB on ‗Honey Gold‘ fruit occurred at a high incidence and a great area on

abraded fruit kept at 16°C (Chapter 5). Moreover, USB occurred on abraded or vibrated fruit grown

in Northern Territory at 12°C, but not USB occurs on fruit that were not abraded or vibrated

(Chapter 5 and 6). Therefore, USB is not simply a chilling injury.

A relatively longer duration (18 h) of vibration at caused a higher incidence of USB on fruit grown

in the Northern Territory as compared to fruit bit exposed to vibration (Chapter 6). Abrasion caused

a higher TUSB incidence than did non-abrasion (Chapter 5). Abrasion tended to cause a higher

incidence and a larger area of AUSB than of EUSB. Therefore, abrasion is most likely a major

contributing factor inducing USB. A higher USB incidence was found on vibrated or abraded fruit

at 12°C than on vibrated or abraded fruit at 20°C. Exposure to low temperature of 10°C caused the

highest severity of AUSB and TUSB. It evidently follows that physical stress as simulated by the

230

abrasion test and vibration is the factor with the most direct elicitation influence on USB expression.

Low temperature exposure intensifies the expression of USB (Figure 8.2).

Higher PPO activity was found in USB affected tissue than in healthy tissue at eating ripe (Chapter

6, Figure 8.2). However, PPO activity was not associated across time with USB expression on fruit.

Similar levels of POD activity and total phenolics concentration were found on the USB affected

tissue and healthy tissue. Therefore, PPO, POD activity and total phenolics concentration in skin

tissue are less possible to be closely associated with USB expression (Figure 8.2). An interesting

observation was that browning in tissue afflicted by USB typically occurred in the cells surrounding

resin ducts in sub-epidermis from anatomical level (Chapter 7, Figure 8.2). Thus, USB is likely to

be related to resin ducts. It is possible that sap leaks from resin ducts into surrounding cells after

physical stresses, and compounds in the sap caused browning (Loveys et al., 1992) by damaging

cell membranes (Knobloch et al., 1989) resulting in PPO in the skin tissue to come in contact with

phenolics (Robinson et al., 1993) (Figure 8.2). Similarly, essential oil leakage from glands on citrus

fruit to surrounding cells has been related to peel pitting on ‗Encore‘ mandarins (Medeira et al.,

1999). In addition, for the vibrated ‗Honey Gold‘ fruit, a relatively higher incidence of USB was

discerned to occur on the fruit ‗shoulder‘ position in the area from the stem scar to the full shoulder

as compared to on the ‗cheek‘ position (Chapter 6, Figure 8.2). This skin region-based differential

expression may suggest that USB is related to the sap remaining inside the mango fruit and moving

towards and expressing from the stem end of the fruit.

From physiological and anatomical observations, spurt sap caused the severe browning which

shows similar browning symptoms (greenish browning plus dark discolouration) as USB (Chapter 7,

Figure 8.2). Greenish browning was found with USB as well as severe browning caused by direct

application of both terpinolene and spurt sap (Chapter 7). It is concluded that terpinolene

contributes greenish browning for USB. The dark discolouration was found in USB and also in the

severe browning caused by spurt sap application. Therefore, other compounds of spurt sap may

contribute to the dark discolouration of typical USB. In addition, the upper-phase from spurt sap

generally caused a higher incidence and severity of severe browning than did spurt sap. Terpinolene

in the upper-phase portion of separated sap from ‗Kensington Pride‘ mango fruit has been suggested

as a particular compound and causes skin browning (Loveys et al., 1992). It may be that a higher

concentration of terpinolene exists in upper-phase spurt sap than in crude spurt sap.

Exposure to low temperature of 12°C intensified the incidence of skin browning caused by sap in

terms of mild, severe and total browning in fruit abrasion, peeling and cut test treatments (Chapter 7,

231

Figure 8.2). These findings were consistent with the higher typical USB incidence on fruit kept at

12°C than on fruit kept at 20°C (Chapter 6 and 7). These observations strengthened the evidence for

more USB incidence on vibrated or abraded fruit at 12°C than at 20°C.

Overall, USB is not simply a chilling injury. USB is not a simply chilling injury. Physical stress

induced USB on ‗Honey Gold‘ mango fruit. It is possible that physical stress causes sap in resin

ducts beneath the skin to leak into surrounding cells and results in browning. Terpinolene in sap

contributes greenish browning for USB and other compounds in sap may be involved in dark

browning for USB by damaging cell membranes which causes PPO to mixture with phenolics. The

low temperature of 12°C evidently exacerbates this sap-mediated browning disorder incidence.

Figure 8.2 A schematic model on the effects on under-skin browning of postharvest treatments

(physical stress: abrasion and vibration, low storage temperature and sap) and the mechanism of

under-skin browning. The red arrow means ‗not influence‘. The black arrow means ‗is related with‘

232

8.3 Findings and Directions for Future Research

8.3.1 Lenticel discolouration

It has been determined conclusively that irradiating fruit at sprung stage can effectively reduce the

LD that develops on irradiated ‗B74‘ mangoes. Moreover, this treatment had no adverse effects on

skin colour, titratable acidity and soluble solids concentration at eating ripe (Chapter 3). Thus, this

practice can be adopted as a postharvest treatment for reducing LD on irradiated ‗B74‘ fruit

(Chapter 3).

Total phenolics concentration was not correlated with the expression of LD induced by irradiation

(Chapter 4). However, PPO activity is evidently involved and POD activity is possibly involved in

the LD expression. With a view to devising alternative and / or improved control measures, more

work on the biochemistry of the mechanism of LD induced by irradiation is warranted. The work

should encompass characterising cell integrity and cell membrane permeability in and around

lenticels. Levels of malondialdehyde (MDA), reactive oxygen species (ROS) and electrolyte

leakage (EL) should be elucidated, as indices of membrane damage (Kovacs and Keresztes, 2002),

to better explain the increase of LD on mango fruit observed after irradiation. The characteristics of

cell ultrastructure as revealed by transmission electron microscopy (Moreno et al., 2006) may help

elucidate the mechanism of LD induced by irradiation.

8.3.2 Under-skin browning

This study has established that transportation and holding of ‗Honey Gold‘ fruit under conditions of

relatively high temperature (i.e. ≥ 16°C) and low physical stress, including from fruit-to-fruit

contact under vibration during transportation, can reduce USB incidence and severity (Chapters 5

and 6) .

As a relatively soft polystyrene liner did not reduce USB incidence, alternative superior in-tray

packing options should be sought and evaluated (Chapter 6). For example, it is perhaps worth trying

/ trialing individual polystyrene / foam nets or tray divider combined with individual polystyrene /

foam nets, as are popularly used on papaya and pear fruit after harvest, during commercial

transportation (Zhou et al., 2008; Chonhenchob and Singh, 2005).

USB is most likely to be a result of damage-induced redistribution in tissues of sap left inside

mango fruit after de-sapping at harvest (Chapter 7). Sap from ‗Honey Gold‘ mango fruit and other

233

mango cultivars should be collected at different times (morning and afternoon) and qualified and

quantified. The biochemical analysis of sap from ‗Honey Gold‘ mango fruit is also worth

investigating. In addition, the compartmentation and composition of sap remaining in resin ducts

underneath mango skin and its interaction with low temperature exposure (Chapter 7) after physical

stress warrant details study at biochemical and anatomical levels. These studies will lead to a better

understanding of the mechanism of USB with a view to informing improved USB management

measures.

References



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317.

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236

Appendices 1.

Table A 1.1 Summary of information on fruit growing region, dry matter content (n = 7 - 10) and dose of γ-irradiation (3 - 4) of ‗B74‘ mango fruit for

experiments.

Dry matter content (%) γ-irradiation (Gy) Company Location

Fruit growing region ean Min Max Mean Min Max

Chemicals and

Waxing

2011 – 12 season Southeast

Queensland

Steritec Narangba, Queensland,

Australia

2012 -13 season Southeast

Queensland

16.4 15.4 17.4 557 524 587 Steritec Narangba, Queensland,

Australia

Bagging


Queensland

Steritec Narangba, Queensland,

Australia

2012 - 13 season Southeast

Queensland


Australia


Queensland


Australia

Northern Territory Northern Territory 14.9 14.5 15.5 491 485 510 Lucas Heights Sydney, NSW, Australia

237

Table A 1.2 Effects of chemical treatments (n = 5) and summary of statistical analyses of factors on LD and skin colour. ‗B74‘ mango fruit from

Southeast Queensland in the 2011 – 12 season dipped in 100 and 500 mM, citric acid and ascorbic acid, and distilled water (control) and subsequently

exposed to γ-irradiation or not. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors repeated

measurement analysis of variance less than 0.05 mean significantly different.

Treatments LD Skin colour

1 5 10 14 1 5 10 14

No irradiation 1 ± 0 1 ± 0 1 ± 0 1.8 ± 0.2 2.8 ± 0.4 4.8 ± 0.4 6 ± 0 6 ± 0

100 mM Citric acid, no irradiation 1 ± 0 1 ± 0 1.2 ± 0.2 1.8 ± 0.2 2.2 ± 0.2 3.4 ± 0.5 5.8 ± 0.2 6 ± 0

500 mM Citric acid, no irradiation 1.4 ± 0.2 1.8 ± 0.4 1.8 ± 0.4 2.8 ± 0.5 2 ± 0.3 3.8 ± 0.6 5 ± 0.6 5.8 ± 0.2

100 mM Ascorbic acid, no irradiation 1 ± 0 1 ± 0 1 ± 0 2.4 ± 0.2 3.4 ± 0.2 6 ± 0 6 ± 0 6 ± 0

500 mM Ascorbic acid, no irradiation 1.4 ± 0.2 1.4 ± 0.2 1.4 ± 0.2 2.8 ± 0.4 2.4 ± 0.4 4.8 ± 0.6 6 ± 0 6 ± 0

irradiation 2.6 ± 0.4 2.6 ± 0.4 2.6 ± 0.4 2.8 ± 0.4 1.4 ± 0.2 1.6 ± 0.2 3.7 ± 0.4 5.2 ± 0.2

100 mM Citric acid, irradiation 2.9 ± 0.3 3 ± 0.3 3.1 ± 0.2 3.2 ± 0.2 1.8 ± 0.4 1.8 ± 0.4 4.6 ± 0.7 5.4 ± 0.2

500 mM Citric acid, irradiation 2.8 ± 0.3 3 ± 0.3 3 ± 0.3 3.1 ± 0.3 2.2 ± 0.4 2.8 ± 0.6 4.3 ± 0.6 5.6 ± 0.2

100 mM Ascorbic acid, irradiation 2.1 ± 0.5 2.7 ± 0.5 2.8 ± 0.6 3 ± 0.5 1.8 ± 0.2 1.8 ± 0.2 3.7 ± 0.4 5.8 ± 0.2

500 mM Ascorbic acid, irradiation 2.2 ± 0.4 2.4 ± 0.2 2.4 ± 0.2 2.4 ± 0.2 1.4 ± 0.2 1.5 ± 0.4 3.3 ± 0.5 5.4 ± 0.2

Factors repeated measurement analysis of variance P value P value

irradiation < 0.001 < 0.001

Chemicals 0.367 0.286

irradiation × chemicals 0.291 0.003

Time < 0.001 < 0.001

Time × irradiation < 0.001 < 0.001

238

Time × chemicals 0.268 0.113

Time× irradiation × chemicals 0.346 0.059

239

Table A 1.3 Effects of chemical treatments (n = 5) and summary of statistical analyses of factors on firmness and skin browning. ‗B74‘ mango fruit

from Southeast Queensland in the 2011 – 12 season dipped in 100 and 500 mM, citric acid and ascorbic acid, and distilled water (control) and

subsequently exposed to γ-irradiation or not. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of

factors repeated measurement analysis of variance less than 0.05 mean significantly different.

Treatments Firmness Skin browning

1 5 10 14 1 5 10 14

No irradiation 1 ± 0 1 ± 0 1 ± 0 1.8 ± 0.2 2.8 ± 0.4 4.8 ± 0.4 6 ± 0 6 ± 0

100 mM Citric acid, no irradiation 1 ± 0 1 ± 0 1.2 ± 0.2 1.8 ± 0.2 2.2 ± 0.2 3.4 ± 0.5 5.8 ± 0.2 6 ± 0

500 mM Citric acid, no irradiation 1.4 ± 0.2 1.8 ± 0.4 1.8 ± 0.4 2.8 ± 0.5 2 ± 0.3 3.8 ± 0.6 5 ± 0.6 5.8 ± 0.2

100 mM Ascorbic acid, no irradiation 1 ± 0 1 ± 0 1 ± 0 2.4 ± 0.2 3.4 ± 0.2 6 ± 0 6 ± 0 6 ± 0

500 mM Ascorbic acid, no irradiation 1.4 ± 0.2 1.4 ± 0.2 1.4 ± 0.2 2.8 ± 0.4 2.4 ± 0.4 4.8 ± 0.6 6 ± 0 6 ± 0

Irradiation 2.6 ± 0.4 2.6 ± 0.4 2.6 ± 0.4 2.8 ± 0.4 1.4 ± 0.2 1.6 ± 0.2 3.7 ± 0.4 5.2 ± 0.2

100 mM Citric acid, irradiation 2.9 ± 0.3 3 ± 0.3 3.1 ± 0.2 3.2 ± 0.2 1.8 ± 0.4 1.8 ± 0.4 4.6 ± 0.7 5.4 ± 0.2

500 mM Citric acid, irradiation 2.8 ± 0.3 3 ± 0.3 3 ± 0.3 3.1 ± 0.3 2.2 ± 0.4 2.8 ± 0.6 4.3 ± 0.6 5.6 ± 0.2

100 mM Ascorbic acid, irradiation 2.1 ± 0.5 2.7 ± 0.5 2.8 ± 0.6 3 ± 0.5 1.8 ± 0.2 1.8 ± 0.2 3.7 ± 0.4 5.8 ± 0.2

500 mM Ascorbic acid, irradiation 2.2 ± 0.4 2.4 ± 0.2 2.4 ± 0.2 2.4 ± 0.2 1.4 ± 0.2 1.5 ± 0.4 3.3 ± 0.5 5.4 ± 0.2


Irradiation 0.816 < 0.001

Chemicals 0.042 0.013

Irradiation × chemicals 0.064 0.018

Time < 0.001 0.064

Time × irradiation < 0.001 0.165

240

Time × chemicals 0.013 0.546

Time× irradiation × chemicals 0.060 0.054

241

Table A 1.4 Effects of chemical treatments (n = 15) on LD and skin browning and summary of statistical analyses of factors on LD and skin browning

in chemical treatments. ‗B74‘ mango fruit dipped in 100 mM calcium chloride, ascorbic acid and calcium ascorbate, 10 mM calcium ascorbate, 50 mM

calcium ascorbate, and distilled water (control) and then subsequently exposed to γ-irradiation or not during the 2012 – 13 season. Data in section of

treatments are expressed as mean and standard error of the mean. Data in section of factors repeated measurement analysis of variance less than 0.05

mean significantly different.

Treatments LD Skin browning

1 5 10 14 1 5 10 14

No irradiation 1.1 ± 0.2 1.3 ± 0.2 1.5 ± 0.2 1.6 ± 0.2 0 ± 0 0.3 ± 0.1 0.4 ± 0.1 0.3 ± 0.1

100 mM Calcium chloride, no irradiation 1.3 ± 0.2 1.5 ± 0.2 1.6 ± 0.2 2.4 ± 0.2 0 ± 0 0.3 ± 0.2 0.6 ± 0.2 0.7 ± 0.3

100 mM Ascorbic acid, no irradiation 1.4 ± 0.2 1.6 ± 0.2 1.7 ± 0.2 2.5 ± 0.2 0.4 ± 0.2 2.1 ± 0.1 2.3 ± 0.1 2.8 ± 0.1

100 mM Calcium ascorbate, no irradiation 1 ± 0.1 1.4 ± 0.2 1.9 ± 0.2 2.4 ± 0.2 0.2 ± 0.1 1.5 ± 0.2 1.8 ± 0.2 2.2 ± 0.2

50 mM Calcium ascorbate, no irradiation 1.5 ± 0.2 1.5 ± 0.2 1.7 ± 0.2 2.2 ± 0.2 0.4 ± 0.2 1.6 ± 0.2 1.7 ± 0.2 1.9 ± 0.2

10 mM Calcium ascorbate, no irradiation 1.7 ± 0.3 1.8 ± 0.3 1.9 ± 0.3 2.6 ± 0.3 0 ± 0 0.4 ± 0.2 0.7 ± 0.2 1 ± 0.3

Irradiation 1.3 ± 0.2 2.5 ± 0.2 2.6 ± 0.2 2.6 ± 0.2 0 ± 0 0.9 ± 0.2 1.1 ± 0.2 1.1 ± 0.2

100 mM Calcium chloride, irradiation 1.6 ± 0.3 3 ± 0.3 3.1 ± 0.3 3.2 ± 0.3 0.2 ± 0.2 0.7 ± 0.2 0.7 ± 0.2 0.7 ± 0.2

100 mM Ascorbic acid, irradiation 1.1 ± 0.1 3.1 ± 0.2 3.2 ± 0.2 3.3 ± 0.2 0 ± 0 3.5 ± 0.3 3.5 ± 0.3 3.5 ± 0.3

100 mM Calcium ascorbate, irradiation 1.1 ± 0.2 2.5 ± 0.2 3 ± 0.3 3.3 ± 0.3 0 ± 0 2.6 ± 0.2 2.6 ± 0.2 2.8 ± 0.2

50 mM Calcium ascorbate, irradiation 1 ± 0.1 2.6 ± 0.3 2.8 ± 0.3 3.2 ± 0.2 0.1 ± 0.1 3 ± 0.2 3 ± 0.2 3.1 ± 0.2

10 mM Calcium ascorbate, irradiation 0.9 ± 0.1 2.4 ± 0.3 2.5 ± 0.3 2.8 ± 0.3 0.1 ± 0.1 2.3 ± 0.3 2.3 ± 0.3 2.3 ± 0.3


irradiation < 0.001 < 0.001

Chemicals 0.409 < 0.001

242

Irradiation × chemicals 0.316 0.052

Time < 0.001 < 0.001


Time × chemicals < 0.001 < 0.001

Time× irradiation × chemicals 0.009 < 0.001

243

Table A 1.5 Effects of waxing treatments (n = 15) and summary of statistical analyses of factors on LD and skin colour in waxing treatments. ‗B74‘

mango fruit was dipped in distilled water (control), 10%, 20%, 40% and 80% carnauba wax for 10 s and subsequently exposed to γ-irradiation or not

on LD during the 2011 – 12 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors

repeated measurement analysis of variance less than 0.05 mean significantly different.

Treatment LD Skin colour

No irradiation 1.0 ± 0.1 1.0 ± 0.1 1.0 ± 0.1 3.9 ± 0.3 4.4 ± 0.4 5.8 ± 0.1

10% Carnauba wax, no irradiation 1.1 ± 0.3 1.4 ± 0.3 1.4 ± 0.3 3.3 ± 0.3 4.7 ± 0.4 5.4 ± 0.3




Irradiation 3.0 ± 0.3 3.2 ± 0.2 3.3 ± 0.2 3.1 ± 0.3 3.2 ± 0.4 4.9 ± 0.5

10% Carnauba wax, irradiation 2.3 ± 0.2 2.9 ± 0.3 3.0 ± 0.3 2.3 ± 0.3 2.7 ± 0.3 3.8 ± 0.5



80% Carnauba wax, irradiation 1.8 ± 0.3 2.4 ± 0.3 2.4 ± 0.3 1.9 ± 0.3 1.8 ± 0.2 3 ± 0.4


Irradiation < 0.001 < 0.001

Waxing 0.321 < 0.001

Irradiation × waxing 0.145 0.343

Time < 0.001 < 0.001


Time × waxing 0.024 0.006

244

Time × irradiation × waxing 0.318 0.218

245

Table A 1.6 Effects of waxing treatments (n = 15) and summary of statistical analyses of factors on firmness in waxing treatments. ‗B74‘ mango fruit

was dipped in distilled water (control), 10, 20, 40 and 80% carnauba wax for 10 s and subsequently exposed to γ-irradiation or not on LD during the

2011 – 12 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors repeated measurement

analysis of variance less than 0.05 mean significantly different.

Treatments Time (days)

Firmness

3 7 10

DW (control), no irradiation 1.1 ± 0.3 2 ± 0.1 3.2 ± 0.1

10% Carnauba wax, no irradiation 0.8 ± 0.1 2.2 ± 0.1 3.1 ± 0.1

20% Carnauba wax, no irradiation 1 ± 0 2.3 ± 0.1 3.2 ± 0.1



Irradiation 0.7 ± 0.2 1.8 ± 0.1 3.1 ± 0.1

10% Carnauba wax, irradiation 0.7 ± 0.2 2.4 ± 0.1 3 ± 0.1

20% Carnauba wax, irradiation 0.8 ± 0.1 2.2 ± 0.1 2.9 ± 0.1

40% Carnauba wax, irradiation 0.6 ± 0.2 2.2 ± 0.1 3 ± 0.1

80% Carnauba wax, irradiation 0.5 ± 0.2 2.2 ± 0.1 2.6 ± 0.1

Factorial repeated measurement analysis of variance P value

irradiation 0.137

Waxing 0.048

Irradiation × waxing 0.722

Time < 0.001

246

Time × irradiation 0.059

Time × waxing 0.001

Time × irradiation × waxing 0.782

247

Table A 1.7 Effects of waxing treatments (n = 15) and summary of statistical analyses of factors on LD and skin colour in waxing treatments. ‗B74‘

mango fruit were dipped into 75% carnauba wax for 1 and 3 times for 10 s, and distilled water (control) and subsequently exposed to γ-irradiation or

not during the 2012 – 13 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors repeated


Treatments Time from irradiation (days)

LD Skin colour

0 4 8 11 14 0 4 8 11 14

No irradiation 1.1 ± 0.2 1.3 ± 0.2 1.5 ± 0.2 1.6 ± 0.2 2 ± 0.2 2.8 ± 0.2 3.9 ± 0.3 5.2 ± 0.2 5.8 ± 0.1 6.0 ± 0.0

1 Layer, no irradiation 1.0 ± 0.1 1.0 ± 0.1 1.1 ± 0.1 1.1 ± 0.1 1.3 ± 0.2 2.3 ± 0.2 3.3 ± 0.3 4.0 ± 0.3 4.9 ± 0.3 5.2 ± 0.2

3 Layers, no irradiation 0.9 ± 0.1 1.5 ± 0.1 1.6 ± 0.1 1.6 ± 0.1 1.7 ± 0.2 2.6 ± 0.2 3.2 ± 0.2 4.2 ± 0.2 4.2 ± 0.2 4.2 ± 0.2

Irradiation 1.2 ± 0.2 2.5 ± 0.2 2.6 ± 0.2 2.7 ± 0.2 2.9 ± 0.2 2.6 ± 0.2 3.3 ± 0.4 4.1 ± 0.3 4.9 ± 0.3 5.3 ± 0.2

1 Layer, irradiation 1.2 ± 0.2 2 ± 0.2 2.2 ± 0.2 2.3 ± 0.2 2.4 ± 0.2 2.9 ± 0.3 3.6 ± 0.3 4 ± 0.3 4.8 ± 0.3 5.4 ± 0.2

3 Layers, irradiation 1.2 ± 0.2 1.2 ± 0.2 1.5 ± 0.2 1.7 ± 0.2 2 ± 0.2 2.6 ± 0.2 3.0 ± 0.2 3.6 ± 0.2 3.6 ± 0.2 3.8 ± 0.2

Factorial repeated measurement analysis of variance

P value P value

Irradiation < 0.001 0.126

Waxing 0.033 0.009


Time < 0.001 < 0.001

Time × irradiation < 0.001 0.038

Time × waxing 0.002 < 0.001

Time × irradiation × waxing < 0.001 0.048

248

Table A 1.8 Effects of waxing treatments (n = 15) and summary of statistical analyses of factors on firmness and weight loss in waxing treatments.

‗B74‘ mango fruit was dipped into 75% carnauba wax for 1 and 3 times, and distilled water (control) for 10 s and subsequently exposed to γ-irradiation

or not during the 2012 – 13 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors

repeated measurement analysis of variance less than 0.05 mean significantly different.


Firmness Weight loss

0 4 8 11 14 4 8 11 14

No irradiation 0 ± 0 0.5 ± 0.1 1.4 ± 0.2 2.7 ± 0.1 3.5 ± 0.1 1.7 ± 0.1 2.7 ± 0.1 3.6 ± 0.1 4.3 ± 0.1

1 Layer, no irradiation 0 ± 0 0.1 ± 0.1 0.5 ± 0.1 1.7 ± 0.2 2.9 ± 0.1 0.6 ± 0 0.9 ± 0 1.2 ± 0 1.7 ± 0.1

3 Layers, no irradiation 0 ± 0 0 ± 0 0 ± 0 0.2 ± 0.1 1.8 ± 0.2 0.5 ± 0 0.7 ± 0 1 ± 0 1.9 ± 0.1

Irradiation 0 ± 0 0.8 ± 0.2 1.8 ± 0.2 3.1 ± 0.2 3.5 ± 0.1 2.1 ± 0.1 3 ± 0.1 4 ± 0.2 4.6 ± 0.2

1 Layer, irradiation 0 ± 0 0.1 ± 0 0.3 ± 0.1 1.5 ± 0.3 2.9 ± 0.1 0.4 ± 0 0.9 ± 0 1.2 ± 0 1.7 ± 0.1

3 Layers, irradiation 0 ± 0 0 ± 0 0 ± 0 0 ± 0 1.3 ± 0.2 0.3 ± 0 1.1 ± 0 1.5 ± 0.1 2.4 ± 0.1


P value P value

Irradiation 0.663 < 0.001

Waxing < 0.001 < 0.001


Time < 0.001 < 0.001

Time × irradiation 0.839 < 0.001

Time × waxing < 0.001 < 0.001

Time × irradiation × waxing 0.325 < 0.001

249

Table A 1.9 Effects of waxing treatments (n = 3) and summary of statistical analyses of factors on titratable acidity (%) and soluble solids

concentration (Brix) in waxing treatments. ‗B74‘ mango fruit was dipped into 75% carnauba wax for 1 time, and distilled water (control) for 10s and

subsequently exposed to γ-irradiation or not during the 2012 – 13 season. Data in section of treatments are expressed as mean and standard error of the

mean. Data in section of factors repeated measurement analysis of variance less than 0.05 mean significantly different.

Treatments Time of eating ripe

Titratable acidity (%) Soluble solids concentration (Brix)

No irradiation 0.1165 ± 0.0029 13.97 ± 0.2

1 Layer of 75% carnauba wax, no irradiation 0.1137 ± 0.0039 14.9 ± 0.61

γ -irradiation 0.1697 ± 0.0035 15.6 ± 0.87

1 Layer of 75% carnauba wax, irradiation 0.1264 ± 0.0106 14.23 ± 0.53

Factorial GANOVA P value P value


Waxing 0.005 0.727


250

Table A 1.10 Effects of bagging treatments (n = 15) and summary of statistical analyses of factors on LD and skin colour in bagging treatments. ‗B74‘

mango fruit treated with polyethylene bagging, polyethylene bagging plus nitrogen flushing and no bag (control) and subsequently exposed to γ-

irradiation or not, and finally removed bag after 1 [24 h] and 2 days‘ [48 h] storage in the 2011 – 12 season. Data in section of treatments are expressed

as mean and standard error of the mean. Data in section of factors repeated measurement analysis of variance less than 0.05 mean significantly

different.


LD Skin colour

3 8 11 3 8 11

No irradiation 1 ± 0.1 1 ± 0.1 1 ± 0.1 3.9 ± 0.3 4.4 ± 0.4 5.8 ± 0.1

Polyethylene bag, no irradiation, remove bag after 24 h 1.1 ± 0.2 1.5 ± 0.2 1.5 ± 0.2 2.5 ± 0.3 4.9 ± 0.4 5.7 ± 0.2

Polyethylene bag with nitrogen, no irradiation, remove bag after 24 h 0.6 ± 0.3 1.3 ± 0.2 1.4 ± 0.2 1.4 ± 0.3 4 ± 0.4 5.8 ± 0.1

Polyethylene bag, no irradiation, remove bag after 48 h 0.8 ± 0.2 1.4 ± 0.2 1.4 ± 0.2 1.7 ± 0.2 3.7 ± 0.5 4.6 ± 0.4

Polyethylene bag with nitrogen, no irradiation, remove bag after 48 h 0.8 ± 0.1 1.3 ± 0.2 1.3 ± 0.2 2.1 ± 0.2 3.8 ± 0.4 5 ± 0.3

Irradiation 3 ± 0.3 3.2 ± 0.2 3.3 ± 0.2 3.1 ± 0.3 3.2 ± 0.4 4.9 ± 0.5

Polyethylene bag, irradiation, remove bag after 24 h 2.9 ± 0.3 3.3 ± 0.3 3.3 ± 0.3 1.6 ± 0.3 1.9 ± 0.4 3.2 ± 0.5

Polyethylene bag with nitrogen, irradiation, remove bag after 24 h 3 ± 0.3 3.3 ± 0.2 3.8 ± 0.1 1.5 ± 0.2 1.5 ± 0.3 2.6 ± 0.4

Polyethylene bag, irradiation, remove bag after 48 h 1.9 ± 0.2 3.5 ± 0.2 3.6 ± 0.2 1.7 ± 0.2 1.9 ± 0.2 2 ± 0.1

Polyethylene bag with nitrogen, irradiation, remove bag after 48 h 1.6 ± 0.2 3.1 ± 0.2 3.3 ± 0.2 1.3 ± 0.2 1.8 ± 0.2 2.2 ± 0.2



Bagging 0.346 < 0.001

Irradiation × bagging 0.314 0.252

251

Time < 0.001 < 0.001


Time × bagging < 0.001 < 0.001

Time × irradiation × bagging < 0.001 < 0.001

252

Table A 1.11 Effects of bagging treatments (n = 15) and summary of statistical analyses of factors on firmness. ‗B74‘ mango fruit treated with

polyethylene bagging, polyethylene bagging plus nitrogen flush and no bag (control) and subsequently exposed to γ-irradiation or not, and finally

removed bag after 1 [24 h] and 2 days‘ [48 h] storage in the 2011 – 12 season. Data in section of treatments are expressed as mean and standard error

of the mean. Data in section of factors repeated measurement analysis of variance less than 0.05 mean significantly different.

Treatments

Time (days)

Firmness

3 8 11

No irradiation 1.1 ± 0.3 2 ± 0.1 3.1 ± 0.1

Polyethylene bag, no irradiation, remove bag after 24 h 0.5 ± 0.2 2.15 ± 0.1 3.5 ± 0.2

Polyethylene bag with nitrogen, no irradiation, remove bag after 24 h 0.5 ± 0.2 2 ± 0.1 3.2 ± 0.1

Polyethylene bag, no irradiation, remove bag after 48 h 0.5 ± 0.2 2.2 ± 0.1 3.3 ± 0.2

Polyethylene bag with nitrogen, no irradiation, remove bag after 48 h 0.7 ± 0.2 2.2 ± 0.1 3.6 ± 0.2

Irradiation 0.7 ± 0.2 1.8 ± 0.1 2.95 ± 0.1

Polyethylene bag, irradiation, remove bag after 24 h 0.3 ± 0.2 1.95 ± 0.1 3.2 ± 0.2

Polyethylene bag with nitrogen, irradiation, remove bag after 24 h 0.8 ± 0.1 1.9 ± 0.2 3.4 ± 0.2

Polyethylene bag, irradiation, remove bag after 48 h 0.6 ± 0.2 2.05 ± 0.1 3.1 ± 0.1

Polyethylene bag with nitrogen, irradiation, remove bag after 48 h 0.4 ± 0.2 1.9 ± 0.1 3.1 ± 0.1

Factors repeated measurement analysis of variance P value

Irradiation 0.034

Bagging 0.994

Irradiation × bagging 0.260

Time < 0.001

253


Time × bagging < 0.001

Time × irradiation × bagging 0.535

254

Table A 1.12 Effects of bagging treatments (n = 15) and summary of statistical analyses of factors on LD and skin colour. ‗B74‘ mango fruit sealed by

macro-perforated bag with and without high RH, polyethylene bag with and without nitrogen, paper bag and no bag, and subsequently exposed to γ-

irradiation or not, and finally bag was removed after 8 days‘ storage during the 2012 – 13 season. Data in section of treatments are expressed as mean

and standard error of the mean. Data in section of factors repeated measurement analysis of variance less than 0.05 mean significantly different.


LD Skin colour

0 8 11 0 8 11

No irradiation 2 ± 0.2 2.6 ± 0.2 2.6 ± 0.2 1.7 ± 0.2 5.3 ± 0.2 5.9 ± 0.1

Polyethylene bag, no irradiation, remove bag after 8 days 1.3 ± 0.1 1.3 ± 0.1 1.6 ± 0.2 2.2 ± 0.2 2.9 ± 0.3 3.7 ± 0.4

Polyethylene bag with nitrogen flush, no irradiation, remove

bag after 8 days

1.2 ± 0.1 1.3 ± 0.1 1.7 ± 0.2 1.9 ± 0.2 2.8 ± 0.2 3.7 ± 0.2

Macro-perforated bag, no irradiation, remove bag after 8 days 1.6 ± 0.2 1.6 ± 0.1 1.6 ± 0.1 2 ± 0.2 2.7 ± 0.2 5 ± 0.2

Macro-perforated bag with high RH, no irradiation, remove bag

after 8 days

1.7 ± 0.2 2.3 ± 0.2 2.3 ± 0.2 2.4 ± 0.1 4.9 ± 0.2 5.5 ± 0.2

Paper bag, no irradiation, remove bag after 8 days 1.4 ± 0.2 1.8 ± 0.1 1.8 ± 0.1 2.1 ± 0.2 5.1 ± 0.2 5.4 ± 0.2

irradiation 1.6 ± 0.2 3.9 ± 0.1 4 ± 0.1 2.5 ± 0.2 3.7 ± 0.1 4.3 ± 0.2

Polyethylene bag, irradiation, remove bag after 8 days 1.9 ± 0.2 2.2 ± 0.2 3.5 ± 0.2 2.1 ± 0.3 2.6 ± 0.3 3.2 ± 0.3

Polyethylene bag with nitrogen flush, irradiation, remove bag

after 8 days

1.6 ± 0.2 1.9 ± 0.2 3.2 ± 0.1 2.1 ± 0.2 2.5 ± 0.2 3.5 ± 0.3

Macro-perforated bag, irradiation, remove bag after 8 days 1.7 ± 0.2 3.5 ± 0.1 3.8 ± 0.1 1.8 ± 0.2 2.8 ± 0.2 4.1 ± 0.2

Macro-perforated bag with high RH, irradiation, remove bag

after 8 days

1.5 ± 0.2 3.9 ± 0.1 4 ± 0.1 2.1 ± 0.2 3.4 ± 0.2 3.8 ± 0.3

255

Paper bag, irradiation, remove bag after 8 days 1.7 ± 0.2 4.2 ± 0.1 4.1 ± 0.1 2.4 ± 0.2 3.4 ± 0.2 4.5 ± 0.2

Factors repeated measurement analysis of variance

P value P value


Bagging < 0.001 < 0.001

Irradiation × bagging 0.005 0.053

Time < 0.001 < 0.001


Time × bagging < 0.001 < 0.001

Time × irradiation × bagging < 0.001 < 0.001

256

Table A 1.13 Effects of bagging treatments (n = 15) and summary of statistical analyses of factors on firmness and weight loss (%). Mature hard ‗B74‘

mango fruit sealed by macro-perforated bag with and without high RH, polyethylene bag with and without nitrogen, paper bag and no bag, and

subsequently exposed to γ-irradiation or not, and finally bag was removed after 8 days‘ storage during the 2012 – 13 season. Data in section of

treatments are expressed as mean and standard error of the mean. Data in section of factors repeated measurement analysis of variance and factors

analysis of variance less than 0.05 mean significantly different.

Treatment Time from irradiation (days)


0 8 11 8 11

No irradiation 0 ± 0 2.4 ± 0.1 3.0 ± 0.1 3.56 ± 0.11 4.17 ± 0.12

Polyethylene bag, no irradiation, remove bag after 8 days 0 ± 0 1.7 ± 0.1 2.0 ± 0.1 1.76 ± 0.06 2.34 ± 0.08

Polyethylene bag with nitrogen flush, no irradiation, remove bag after 8 days 0 ± 0 1.3 ± 0.4 1.8 ± 0.4 1.87 ± 0.07 2.47 ± 0.08

Macro-perforated bag, no irradiation, remove bag after 8 days 0 ± 0 2.3 ± 0.4 3.1 ± 0.4 1.22 ± 0.03 1.78 ± 0.04

Macro-perforated bag with high humdiity, no irradiation, remove bag after 8 days 0 ± 0 2.7 ± 0.1 3.3 ± 0.1 1.21 ± 0.04 1.77 ± 0.05

Paper bag, no irradiation, remove bag after 8 days 0 ± 0 2.6 ± 0.1 3.3 ± 0.1 2.62 ± 0.06 3.22 ± 0.07

Irradiation 0 ± 0 2.8 ± 0.1 3.2 ± 0.1 3.59 ± 0.13 4.17 ± 0.15

Polyethylene bag, irradiation, remove bag after 8 days 0 ± 0 0.7 ± 0.2 1.3 ± 0.2 2.24 ± 0.09 2.9 ± 0.12

Polyethylene bag with nitrogen flush, irradiation, remove bag after 8 days 0 ± 0 0.8 ± 0.2 1.7 ± 0.2 2.2 ± 0.06 2.8 ± 0.08

Macro-perforated bag, irradiation, remove bag after 8 days 0 ± 0 1.7 ± 0.1 3.0 ± 0.1 1.16 ± 0.02 1.84 ± 0.05

Macro-perforated bag with high RH, irradiation, remove bag after 8 days 0 ± 0 1.9 ± 0.1 3.0 ± 0.1 1.1 ± 0.03 1.77 ± 0.04

Paper bag, irradiation, remove bag after 8 days 0 ± 0 2.2 ± 0.1 3.3 ± 0.1 2.94 ± 0.1 3.55 ± 0.12

Factors repeated measurement analysis of variance Factors analysis of variance

P value P value P value

257

Irradiation 0.006 < 0.001 < 0.001

Bagging < 0.001 < 0.001 < 0.001

Irradiation × bagging 0.104 < 0.001 0.009

Time < 0.001

Time × irradiation < 0.001

Time × bagging < 0.001

Time × irradiation × bagging 0.048

258

Table A 1.14 Effects of bagging treatments (n = 10) and summary of statistical analyses of factors on LD and skin colour. Hard mature ‗B74‘ fruit

reached to hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH, and then was sealed by polyethylene bag with

and without nitrogen, and no bag (control) and subsequently exposed to γ-irradiation or not, and finally bag was removed after 8 days‘ storage during

the 2013 – 14 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors repeated



LD Skin colour

0 8 11 0 8 11

Hard, no irradiation 1.0 ± 0.0 2.1 ± 0.1 2.4 ± 0.2 1.2 ± 0.1 3.7 ± 0.3 5.8 ± 0.1

Hard, polyethylene bag, no irradiation, remove bag after 8 days 1.1 ± 0.1 1.1 ± 0.2 1.6 ± 0.4 1.2 ± 0.1 2.3 ± 0.2 3.3 ± 0.5

Hard, polyethylene bag with nitrogen flush, no irradiation, remove bag after

8 days

1.0 ± 0.1 1.0 ± 0.1 2.2 ± 0.2 1.1 ± 0.1 2.2 ± 0.3 4.8 ± 0.4

Rubbery, no irradiation 1.5 ± 0.2 2.3 ± 0.2 3.4 ± 0.2 2.1 ± 0.2 5.1 ± 0.2 6.0 ± 0.0

Rubbery, polyethylene bag, no irradiation, remove bag after 8 days 1.3 ± 0.2 1.3 ± 0.2 2.2 ± 0.4 2.5 ± 0.2 3.6 ± 0.4 4.5 ± 0.5

Rubbery, polyethylene bag with nitrogen flush, no irradiation, remove bag

after 8 days

1.2 ± 0.1 1.2 ± 0.1 1.9 ± 0.2 2.5 ± 0.3 3.5 ± 0.4 5.1 ± 0.4

Sprung, no irradiation 1.7 ± 0.2 2.8 ± 0.2 3.1 ± 0.2 4.2 ± 0.2 6 ± 0 6 ± 0

Sprung, polyethylene bag, no irradiation, remove bag after 8 days 1.5 ± 0.2 1.5 ± 0.2 3.2 ± 0.3 4.2 ± 0.3 4.8 ± 0.4 5.2 ± 0.3

Sprung, polyethylene bag with nitrogen flush, no irradiation, remove bag

after 8 days

1.9 ± 0.2 2 ± 0.3 3.2 ± 0.4 4.5 ± 0.4 4.8 ± 0.4 5.5 ± 0.3

Hard, irradiation 1.2 ± 0.1 4.6 ± 0.2 4.9 ± 0.1 1.4 ± 0.2 2.9 ± 0.2 3.6 ± 0.3

Hard, polyethylene bag, irradiation, remove bag after 8 days 1.4 ± 0.2 1.6 ± 0.2 3.8 ± 0.2 1.3 ± 0.2 2.2 ± 0.3 3.2 ± 0.5

259

Hard, polyethylene bag with nitrogen flush, irradiation, remove bag after 8

days

1.1 ± 0.1 1.4 ± 0.2 3.6 ± 0.3 1.5 ± 0.2 2.5 ± 0.3 3.7 ± 0.4

Rubbery, irradiation 1.5 ± 0.2 4.6 ± 0.2 4.6 ± 0.2 2.4 ± 0.3 4 ± 0.5 5.4 ± 0.3

Rubbery, polyethylene bag, irradiation, remove bag after 8 days 1.3 ± 0.2 1.4 ± 0.2 3.8 ± 0.4 2.4 ± 0.3 3.2 ± 0.4 4.1 ± 0.4

Rubbery, polyethylene bag with nitrogen flush, irradiation, remove bag after

8 days

1.4 ± 0.2 1.4 ± 0.2 3.4 ± 0.3 2.1 ± 0.2 2.8 ± 0.3 4.3 ± 0.4

Sprung, irradiation 1.8 ± 0.2 4.3 ± 0.2 4.3 ± 0.2 4.6 ± 0.3 6 ± 0 6 ± 0

Sprung, polyethylene bag, irradiation, remove bag after 8 days 1.2 ± 0.1 1.2 ± 0.1 3.9 ± 0.2 4 ± 0.2 5.2 ± 0.3 6 ± 0

Sprung, polyethylene bag with nitrogen flush, irradiation, remove bag after 8

days

1.6 ± 0.2 1.6 ± 0.2 3.6 ± 0.2 4.6 ± 0.4 5.3 ± 0.3 5.6 ± 0.2


Fruit ripeness <.001 <.001

Irradiation <.001 0.088

Bagging <.001 <.001

Ripeness × irradiation <.001 0.032

Ripeness × bagging 0.189 0.708

Irradiation × bagging <.001 0.335

Fruit ripeness × irradiation × bagging 0.719 0.665

Time <.001 <.001

Time × fruit ripeness 0.371 <.001

Time × irradiation <.001 <.001

Time × bagging <.001 <.001

260

Time × fruit ripeness × irradiation 0.024 <.001

Time× fruit ripeness × bagging 0.001 0.007

Time× irradiation× bagging <.001 <.001

Time× fruit ripeness × irradiation× bagging 0.351 0.549

261

Table A 1.15 Effects of bagging treatments (n = 10) and summary of statistical analyses of factors on firmness and weight loss. Hard mature ‗B74‘

fruit reached to hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH, and then was sealed by polyethylene bag

with and without nitrogen, and no bag (control) and subsequently exposed to γ-irradiation or not, and finally bag was removed after 8 days‘ storage

during the 2013 – 14 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section of factors repeated

measurement analysis of variance and factors analysis of variance less than 0.05 mean significantly different.



0 8 11 8 11

Hard, no irradiation 0 ± 0 2.3 ± 0.2 3 ± 0 2.73 ± 0.07 4.00 ± 0.08

Hard, polyethylene bag, no irradiation, remove bag after 8 days 0 ± 0 0.9 ± 0.3 1.8 ± 0.3 1.92 ± 0.1 3.35 ± 0.24

Hard, polyethylene bag with nitrogen flush, no irradiation, remove bag after

8 days

0 ± 0 1.8 ± 0.3 2.3 ± 0.3 2.03 ± 0.08 3.44 ± 0.11

Rubbery, no irradiation 1 ± 0.1 2.5 ± 0.2 3.1 ± 0.1 2.88 ± 0.14 4.21 ± 0.17

Rubbery, polyethylene bag, no irradiation, remove bag after 8 days 1 ± 0.1 1.5 ± 0.3 2.2 ± 0.2 1.93 ± 0.09 3.11 ± 0.17

Rubbery, polyethylene bag with nitrogen flush, no irradiation, remove bag

after 8 days

1.2 ± 0.1 1.5 ± 0.2 2.4 ± 0.2 1.84 ± 0.08 3.02 ± 0.14

Sprung, no irradiation 2.2 ± 0.1 3 ± 0 4 ± 0 2.40 ± 0.11 3.86 ± 0.17

Sprung, polyethylene bag, no irradiation, remove bag after 8 days 2.2 ± 0.1 2.9 ± 0.1 3.4 ± 0.1 1.66 ± 0.05 3.23 ± 0.11

Sprung, polyethylene bag with nitrogen flush, no irradiation, remove bag

after 8 days

2.3 ± 0.2 2.8 ± 0.2 3.8 ± 0.2 1.96 ± 0.09 3.74 ± 0.16

Hard, irradiation 0.9 ± 0.1 2 ± 0 2.9 ± 0.1 2.89 ± 0.1 4.35 ± 0.16

Hard, polyethylene bag, irradiation, remove bag after 8 days 0 ± 0 2.3 ± 0.2 2.9 ± 0.2 2.11 ± 0.1 3.60 ± 0.12

262

Hard, polyethylene bag with nitrogen flush, irradiation, remove bag after 8

days

0 ± 0 1 ± 0.3 1.6 ± 0.4 2.08 ± 0.06 3.46 ± 0.1

Rubbery, irradiation 0 ± 0 1.1 ± 0.3 1.6 ± 0.4 3.04 ± 0.11 4.43 ± 0.15

Rubbery, polyethylene bag, irradiation, remove bag after 8 days 1 ± 0.1 2.2 ± 0.1 2.7 ± 0.1 2.19 ± 0.07 3.30 ± 0.10

Rubbery, polyethylene bag with nitrogen flush, irradiation, remove bag after

8 days

0.9 ± 0.1 1.8 ± 0.2 2.8 ± 0.2 2.00 ± 0.08 3.16 ± 0.13

Sprung, irradiation 2.4 ± 0.1 3.2 ± 0.1 4 ± 0 2.69 ± 0.11 4.2 ± 0.17

Sprung, polyethylene bag, irradiation, remove bag after 8 days 2.4 ± 0.1 3.1 ± 0.1 3.9 ± 0.1 1.88 ± 0.09 3.43 ± 0.16

Sprung, polyethylene bag with nitrogen flush, irradiation, remove bag after 8

days

2.6 ± 0.1 3.1 ± 0.1 3.7 ± 0.1 1.96 ± 0.11 3.55 ± 0.18

Factors repeated measurement analysis of variance Factors analysis of

variance


Ripeness <.001 <.001 0.136

irradiation 0.593 <.001 0.017

Bagging <.001 <.001 <.001

Fruit ripeness × irradiation 0.06 0.844 0.875

Fruit ripeness × bagging 0.002 0.011 0.002

irradiation × bagging 0.102 0.291 0.172

Fruit ripeness × irradiation × bagging 0.198 0.859 0.855

Time <.001

Time × fruit ripeness <.001

263


Time × bagging <.001

Time × fruit ripeness × irradiation 0.05

Time× fruit ripeness × bagging 0.001

Time× irradiation× bagging 0.352

Time× fruit ripeness × irradiation× bagging 0.073

264

Table A 1.16 Effects of bagging treatments (n = 10) and summary of statistical analyses of factors on LD and skin colour. Hard mature ‗B74‘ fruit

grown in Southeast Queensland reached to hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH. They were

then was sealed by polyethylene bag with and without nitrogen, and no bag (control) and subsequently exposed to γ-irradiation or not, and finally bag

was removed after 8 days‘ storage during the 2013 – 14 season. Data in section of treatments are expressed as mean and standard error of the mean.

Data in section of factors repeated measurement analysis of variance less than 0.05 mean significantly different.


LD Skin colour

0 1 3 5 8 12 0 1 3 5 8 12

Hard, no irradiation 1.0 ±

0.0

1.1 ±

0.1

1.3 ±

0.1

1.3 ±

0.1

1.8 ±

0.1

2.2 ±

0.2

1.2 ±

0.1

1.7 ±

0.2

2.3 ±

0.2

2.9 ±

0.2

3.7 ±

0.3

5.8 ±

0.1

Hard, irradiation 1.2 ±

0.1

2.5 ±

0.2

3.9 ±

0.1

4.3 ±

0.2

4.6 ±

0.2

4.9 ±

0.1

1.4 ±

0.2

1.8 ±

0.2

2 ±

0.1

3.0 ±

0.3

3.2 ±

0.3

3.7 ±

0.3

Rubbery, no irradiation 1.5 ±

0.2

1.6

±0.2

1.8 ±

0.2

2.0 ±

0.2

2.2 ±

0.2

3.3 ±

0.2

2.1 ±

0.2

2.6 ±

0.2

3.2 ±

0.2

4.2 ±

0.3

5.1 ±

0.3

6.0 ±

0.0

Rubbery, irradiation 1.4 ±0.2 1.9

±0.2

3.7 ±

0.2

4.3 ±

0.3

4.6

±0.2

4.6 ±

0.2

2.3 ±

0.3

2.9 ±

0.5

3.3 ±

0.4

3.6 ±

0.5

4.0 ±

0.5

5.4 ±

0.3

Sprung, no irradiation 1.5 ±

0.2

1.7

±0.2

1.8

±0.2

2.0

±0.2

2.6

±0.2

3.0 ±

0.2

4.2 ±

0.2

4.2 ±

0.3

5.4 ±

0.2

5.9 ±

0.1

6.0 ±

0.0

6.0 ±

0.0

Sprung, irradiation 1.6 ±

0.2

2.0

±0.1

2.4

±0.2

3.4

±0.1

4.4

±0.2

4.4 ±

0.2

4.6 ±

0.3

4.7 ±

0.3

5.6 ±

0.3

6.0 ±

0.0

6.0 ±

0.0

6.0 ±

0.0

Factors repeated measurement

analysis of variance

P value P value

265


Fruit ripeness 0.222 < 0.001

Fruit ripeness × irradiation < 0.001 0.311

Time < 0.001 < 0.001

Time × γ -irradiation < 0.001 < 0.001

Time × ripeness <

0 001

< 0.001

Time × γ –irradiation × ripeness 0.001 < 0.001

266

Table A 1.17 Effects of bagging treatments (n = 10) and summary of statistical analyses of factors on firmness, weight loss, soluble solids

concentration (SSC) and titratable acidity (TA) at eating ripe. Hard mature ‗B74‘ fruit grown in Southeast Queensland reached to hard, rubbery and

sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100% RH. They were then sealed by polyethylene bag with and without nitrogen, and

no bag (control) and subsequently exposed to γ-irradiation or not, and finally bag was removed after 8 days‘ storage during the 2013 – 14 season. Data

in section of treatments are expressed as mean and standard error of the mean. Data in section of factors analysis of variance less than 0.05 mean

significantly different.

Treatments Time of eating ripe

LD Skin colour Firmness Weight loss SSC TA

Hard, no irradiation 2.4 ± 0.2 5.8 ± 0.1 2.9 ± 0.1 3.51 ± 0.06 13.1 ± 0.3 0.18 ± 0.01

Rubbery, no irradiation 2.5 ± 0.2 5.7 ± 0.2 3.1 ± 0.1 3.16 ± 0.15 13.2 ± 0.3 0.17 ± 0.02

Sprung, no irradiation 2.3 ± 0.2 6 ± 0 2.7 ± 0.1 1.53 ± 0.07 14.1 ± 1.2 0.17 ± 0.00

Hard, irradiation 4.9 ± 0.1 3.5 ± 0.3 2.9 ± 0.2 3.71 ± 0.14 14.4 ± 0.8 0.23 ± 0.02

Rubbery, irradiation 4.6 ± 0.2 4.6 ± 0.4 3 ± 0 2.91 ± 0.07 11.6 ± 1.1 0.21 ± 0.02

Sprung, irradiation 3.4 ± 0.1 5.6 ± 0.3 3.1 ± 0.1 1.78 ± 0.07 14.7 ± 1.1 0.15 ± 0.03

Factorial GNOVA P value P value P value P value P value P value

Irradiation < 0.001 < 0.001 0.132 0.399 0.072 0.101

Fruit ripeness < 0.001 < 0.001 0.190 < 0.001 0.175 0.893

Irradiation × fruit ripeness < 0.001 0.001 0.070 0.027 0.095 0.249

267

Table A 1.18 Effect of fruit ripeness treatments (n = 10) and summary of statistical analyses of factors on LD, skin colour and weight loss at eating

ripe. Mature hard‗B74‘ fruit grown in Northern Territory reached to hard, rubbery and sprung after 0, 5 and 8 days in a ripening room at 20°C and 90 –

100% RH. They were then sealed by polyethylene bag with and without nitrogen, and no bag (control) and subsequently exposed to γ-irradiation or

not, and finally bag was removed after 8 days‘ storage during the 2013 – 14 season. Data in section of treatments are expressed as mean and standard

error of the mean. Data in section of factors analysis of variance less than 0.05 mean significantly different.

Time of eating ripe

Treatments LD Skin colour Weight loss

Hard, no irradiation 0.8 ± 0.1 5.6 ± 0.2 3.51 ± 0.06

Rubbery, no irradiation 1.2 ± 0.1 5.9 ± 0.1 3.16 ± 0.15

Sprung, no irradiation 1 ± 0.1 5.7 ± 0.2 1.53 ± 0.07

Hard, irradiation 3.2 ± 0.2 5.7 ± 0.2 3.71 ± 0.14

Rubbery, irradiation 2.2 ± 0.2 6 ± 0 2.91 ± 0.07

Sprung, irradiation 1.9 ± 0.2 5.8 ± 0.1 1.78 ± 0.07

Factors analysis of variance P value P value P value

Irradiation < 0.001 0.639 0.487

Fruit ripeness 0.002 0.134 < 0.001

Irradiation × fruit ripeness < 0.001 0.679 < 0.001

268

Table A 1.19 Effect of fruit ripeness treatments (n = 10) and summary of statistical analyses of factors on LD, skin colour and firmness. Mature

hard‗B74‘ fruit grown in Northern Territory reached to hard, rubbery and sprung after 0, 5 and 8 days in a ripening room at 20°C and 90 – 100% RH.

They were then sealed by polyethylene bag with and without nitrogen, and no bag (control) and subsequently exposed to γ-irradiation or not, and

finally bag was removed after 8 days‘ storage during the 2013 – 14 season. Data in section of treatments are expressed as mean and standard error of

the mean. Data in section of factors repeated measurement analysis of variance and factors analysis of variance less than 0.05 mean significantly

different.


LD Skin

colour

Firmness Weight

loss

0 1 4 0 1 4 0 1 4 1 4

Hard, no

irradiation

0.9 ± 0.1 0.9 ± 0.1 1.1 ± 0.1 2.6 ± 0.3 2.9 ± 0.4 4.3 ± 0.4 0 ± 0 0 ± 0 1 ± 0.1 0.55 ±

0.02

1.77 ±

0.05

Hard,

irradiation

1.6 ± 0.2 2.7 ± 0.2 2.8 ± 0.2 1.9 ± 0.2 2.1 ± 0.3 2.9 ± 0.3 0 ± 0 0 ± 0 1 ± 0.1 0.66 ±

0.01

1.9 ±

0.07

Rubbery, no

irradiation

1.4 ± 0.1 1.3 ± 0.1 1.3 ± 0.1 3.7 ± 0.4 4.9 ± 0.2 5.7 ± 0.1 0.9 ± 0.1 1.6 ± 0.1 2.2 ± 0.1 1.17 ±

0.04

2.6 ±

0.09

Rubbery,

irradiation

1.1 ± 0.1 1.5 ± 0.2 1.9 ± 0.1 4.4 ± 0.4 5.2 ± 0.2 5.7 ± 0.1 1.1 ± 0.1 1.7 ± 0.1 2.4 ± 0.1 0.99 ±

0.04

2.21 ±

0.08

Sprung, no

irradiation

1.3 ± 0.1 1.3 ± 0.1 1.3 ± 0.1 5.7 ± 0.2 5.7 ± 0.2 5.7 ± 0.2 2.6 ± 0.1 3 ± 0 3 ± 0 0.87 ±

0.04

1.78 ±

0.08

Sprung,

irradiation

0.9 ± 0.1 1.5 ± 0.1 2 ± 0.1 5.8 ± 0.1 5.8 ± 0.1 5.8 ± 0.1 2.7 ± 0.1 3 ± 0 3.2 ± 0.1 0.92 ±

0.04

1.93 ±

0.07

269

Factorial repeated measurement ANOVA Factorial GANOVA

P value P value P value P value P value

irradiation < 0.001 0.282 0.232 0.298 0.294

Fruit

ripeness

0.060 < 0.001 < 0.001 < 0.001 < 0.001

Fruit

ripeness ×

irradiation

< 0.001 0.008 0.697 0.034 0.002

Time < 0.001 < 0.001 < 0.001

Time ×

irradiation

< 0.001 0.050 0.930

Time × fruit

ripeness

0.005 < 0.001 < 0.001

Time ×

irradiation ×

fruit ripeness

0.012 0.396 0.556

270

Table A 1.20 Effect of fruit ripeness and summary of statistical analyses of factors on LD and skin colour (n = 10). Mature hard‗B74‘ fruit grown in

Northern Territory reached to hard or rubbery or sprung after 0 or 5 or 8 days at ripening room (20°C, RH = 90 – 100%) and then was sealed by

polyethylene bag with or without nitrogen or no bag (control) and subsequently experienced with 0 or 576 Gy (493 – 716 Gy) γ-irradiation, and finally

bag was removed after eight days‘ storage in 2013 – 14 season. Data in section of treatments are expressed as mean and standard error of mean

followed by. Data in section of factors analysis of variance less than ≤ 0.05 means significant different.

Ripen time

Treatments LD Skin colour

Hard, non-γ-irradiation 0.8 ± 0.1 5.6 ± 0.2

Rubbery, non-γ-irradiation 1.2 ± 0.1 5.9 ± 0.1

Sprung, non-γ-irradiation 1.0 ± 0.1 5.7 ± 0.2

Hard, γ-irradiation 3.2 ± 0.2 5.7 ± 0.2

Rubbery, γ-irradiation 2.2 ± 0.2 6.0 ± 0.0

Sprung, γ-irradiation 1.9 ± 0.2 5.8 ± 0.1

Factors analysis of variance

P alue P value

Irradiation <0.001 0.639

Ripeness 0.002 0.134

Irradiation. Ripeness <0.001 0.679

271

Appendices 2.

Figure A 2.1 Transverse sections with O-toluidine blue stain hand sections of LD through irradiated

and ripened ‗B74‘ mango fruit skin samples (A): [× 4], (B): [× 10], (C) [× 20]. Scale bars in A, B

and C represent 100 µm, 50 µm and 20 µm respectively. RD: resin duct. L: lenticel cavity.

A B

C

272

Table A 2.1 Effects of treatments on total phenolics concentration (mg GA equivalents / g FW), PPO activity (units / mg protein) and POD activity

(units / mg protein) and its summary of statistical analyses by factors (n = 3). Hard green mature ‗B74‘ fruit grown in Southeast Queensland reached

hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100 % RH. Fruit were subsequently exposed to either 0 or 576 Gy

(493 – 716 Gy) γ-irradiation in the 2013-14 season. Data in section of treatments are expressed as mean and standard error of the mean. Data in section

of factors general analysis of variance less than 0.05 means significantly different.

Treatments Total phenolics concentration

(mg GA equivalents / g FW)

PPO activity

(units / mg protein)

POD activity

(units / mg protein)

Hard, non-irradiation 18.61 ± 0.55 28.38 ± 3.04 28.14 ± 2.78

Hard, irradiation 21.92 ± 1.07 65.63 ± 7.47 56.62 ± 9.60

Rubbery, non-irradiation 22.70 ± 2.04 21.73 ± 1.54 25.25 ± 4.12

Rubbery, irradiation 19.53 ± 0.78 44.09 ± 3.14 52.91 ± 1.76

Sprung, non-irradiation 20.71 ± 0.34 21.73 ± 44.09 24.12 ± .013

Sprung, irradiation 16.34 ± 2.23 26.09 ± 3.02 34.22 ± 1.09

Factorial GANOVA P value P value P value

Irradiation 0.232 < 0.001 < 0.001

Fruit ripeness stage 0.199 0.028 0.031

Irradiation. fruit ripeness stage 0.034 0.288 0.110

273

Table A 2.2 Effects of treatments on total phenolics concentration (mg GA equivalents / g FW) (n = 3), PPO activity (units / mg protein) (n = 3) and

POD activity (units / mg protein) (n = 3) and its summary of statistical analyses by factors. Hard green mature ‗B74‘ fruit grown in Southeast

Queensland reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100 % RH. Fruit were subsequently exposed to

either 0 or 576 Gy (493 – 716 Gy) γ-irradiation in the 2013-14 season. Data in section of treatments are expressed as mean and standard error of the

mean. Data in section of factors general analysis of variance less than 0.05 mean significantly different.


0 1 3 5 8 12

Hard, non-irradiation 7.10 ± 0.46 7.16 ± 0.53 9.84 ± 2.56 8.35 ± 1.43 17.62 ± 0.91 18.61 ± 0.55

Hard, irradiation - 10.57 ± 0.11 7.24 ± 0.34 10.57 ± 0.24 22.94 ± 0.55 21.92 ± 1.07

Rubbery, non-irradiation 7.75 ± 0.33 7.87 ± 0.44 8.66 ± 2.08 15.02 ± 2.30 22.7 ± 2.04 22.7 ± 1.77

Rubbery, irradiation - 15.82 ± 0.74 11.12 ± 2.26 17.09 ± 3.27 19.53 ± 0.78 20.29 ± 1.13

Sprung, non-irradiation 15.18 ± 0.64 12.8 ± 0.45 20.71 ± 0.34 15.64 ± 3.09 22.25 ± 1.54 19.43 ± 3.05

Sprung, irradiation - 10.7 ± 1.20 16.34 ± 2.2 14.84 ± 2.83 23.19 ± 0.79 19.01 ± 1.07

Factorial GANOVA P value

Irradiation 0.168

Fruit ripeness stage < 0.001

Time < 0.001

Irradiation × fruit ripeness stage 0.036

Irradiation × time 0.163

Ripeness × time < 0.001

Irradiation × fruit ripeness stage × time 0.051

274

Table A 2.3 Effects of treatments on PPO activity (units / mg protein) (n = 3) and summary of statistical analyses of factors. Hard green mature ‗B74‘

fruit grown in Southeast Queensland reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100 % RH. Fruit were

subsequently exposed to either 0 or 576 Gy (493 – 716 Gy) γ-irradiation in the 2013-14 season. Data in section of treatments are expressed as mean

and standard error of the mean. Data in section of factors general analysis of variance less than 0.05 mean significantly different.


0 1 3 5 8 12


Hard, irradiation 48.26 ± 1.83 118.8 ± 22.59 145.32 ± 5.55 41.96 ± 4.78 65.63 ± 7.47


Rubbery, irradiation 31.79 ± 1.10 52.22 ± 7.10 99.93 ± 5.74 44.09 ± 3.14 82.08 ± 7.42

Sprung, non-irradiation 48.66 ± 1.83 44.5 ±11.55 26.09 ± 3.02 69.23 ± 6.14 26.6 ± 1.89 31.21 ± 7.45

Sprung, irradiation 67.98 ± 20.95 58.98 ± 6.37 27.93 ± 0.79 45.35 ± 1.59 61.00 ± 8.91


Irradiation < 0.001

Fruit ripeness stage < 0.001

Time < 0.001

Irradiation × fruit ripeness stage < 0.001


Time × fruit ripeness stage < 0.001

Time × irradiation × fruit ripeness stage < 0.001

275

Table A 2.4 Effects of treatments on POD activity (units / mg protein) (n = 3) and summary of statistical analyses by factors. Hard green mature ‗B74‘

fruit grown in southeast Queensland reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and 90 – 100 % RH

respectively and subsequently exposed to either 0 or 576 Gy (493 – 716 Gy) γ-irradiation in the 2013 – 14 season. Data in section of treatments are

expressed as mean and standard error of the mean. Data in section of factors general analysis of variance less than 0.05 mean significantly different.


0 1 3 5 8 12


Hard, irradiation - 29.05 ± 1.94 53.38 ± 6.09 38.66 ± 0.57 52.63 ± 6.21 56.62 ± 9.60


Rubbery, irradiation - 40.55 ± 1.55 42.52 ± 2.92 34.83 ± 1.99 52.91 ± 1.76 54.14 ± 18.31

Sprung, non-irradiation 26.96 ± 5.40 30.89 ± 2.80 24.12 ± 0.13 26.17 ± 1.31 40.97 ± 0.80 35.58 ± 9.96

Sprung, irradiation - 29.3 ± 4.92 34.22 ± 1.09 29.31 ± 1.39 46.29 ± 2.39 55.22 ± 7.53


Irradiation < 0.001

Fruit ripeness stage 0.108

Time < 0.001

Irradiation × Fruit ripeness stage 0.075

Irradiation × time < 0.001

Fruit ripeness stage × time 0.142


276

Table A 2.5 Effect of treatments on total phenolics concentration (mg GA equivalents / g FW) (n =

3) and its summary of statistical analyses by factors. Hard mature ‗B74‘ fruit grown in Southeast

Queensland reached hard, rubbery and sprung after 0, 3 and 8 days in a ripening room at 20°C and

90 – 100% RH. The fruit were polyethylene bagged and not, and subsequently exposed to either 0

or 576 Gy (493 – 716 Gy) γ-irradiation in the 2013 – 14 season. Data in section of treatments are

expressed as mean and standard error of the mean. Data in section of factors general analysis of

variance less than 0.05 mean significantly different. The data at day 0 is not involved in statistical

analyses.


0 8 12

Hard, no bagging, no irradiation 7.10 ± 0.46 17.62 ± 0.91 18.61 ± 0.55

Hard, bagging, no irradiation 19.76 ± 1.45 23.57 ± 2.16

Hard, no bagging, Irradiation 22.94 ± 0.55 21.92 ± 1.07


Rubbery, no bagging, irradiation 7.75 ± 0.33 22.70 ± 2.04 22.7 ± 0.16

Rubbery, bagging, no irradiation 18.43 ± 0.63 23.25 ± 0.45

Rubbery, no bagging, irradiation 19.53 ± 0.78 20.29 ± 0.58

Rubbery, bagging, irradiation 23.73 ± 2.1 20.07 ± 0.16

Sprung, no bagging, no irradiation 15.18 ± 0.64 22.25 ± 1.55 19.43 ± 1.76

Sprung, bagging, no irradiation 23.45 ± 0.29 16.98 ± 1.82

Sprung, no bagging, irradiation 23.19 ± 0.79 19.01 ± 1.13

Sprung, bagging, irradiation 20.69 ± 1.21 19.10 ± 1.34

General Factorial GANOVA P value

Irradiation 0.660


Bagging 0.989

Time 0.278


Irradiation × bagging 0.539

Fruit ripeness stage × bagging 0.433


Time × fruit ripeness stage < 0.001

Time × bagging. 0.445

Irradiation × fruit ripeness stage × bagging 0.006

277


Irradiation × bagging × time 0.678

Fruit ripeness stage × bagging × time 0.424

Irradiation × fruit ripeness stage × bagging

× time

0.024

278

Table A 2.6 Effect of treatments on PPO activity (units / mg protein) (n = 3) and its summary of

statistical analyses by factors. Hard mature ‗B74‘ fruit grown in Southeast Queensland reached

hard, rubbery and sprung after 0, 3 and 8 days in ripening room at 20°C and 90 – 100 % RH

respectively. The fruit were polyethylene bagged and not, and subsequently exposed to either 0 or

576 Gy (493 – 716 Gy) γ-irradiation in the 2013 – 14 season. Data in section of treatments are

expressed as mean and standard error of the mean. Data in section of factors general analysis of

variance less than 0.05 mean significantly different. Data of the day 0 are not involved in statistical

analyses.


0 8 12



Hard, no bagging, irradiation 41.96 ± 4.78 65.63 ± 7.47

Hard, bagging, irradiation 20.55 ± 1.63 26.22 ± 3.23

Rubbery, no bagging, no irradiation 39.18 ± 2.37 21.73 ± 1.54 34.70 ± 2.01





Sprung, bagging, no irradiation 21.50 ± 1.05 23.2 ±8.53



General Factorial GANOVA P value

Irradiation < 0.001


Bagging < 0.001

Time < 0.001


Irradiation × bagging < 0.001


Irradiation × time < 0.001


Bagging × time 0.011


279



Fruit ripeness stage × bagging × time < 0.001

Irradiation × fruit ripeness stage × bagging

× time

0.062

280

Table A 2.7 Effect of treatments on POD activity (units / mg protein) (n = 3) and its summary of

statistical analyses by factors. Hard mature ‗B74‘ fruit grown in southeast Queensland reached hard,

rubbery and sprung after 0, 3 and 8 days in ripening room at 20°C and 90 – 100 % RH respectively.

The fruit were either polyethylene bagged or not and subsequently exposed to either 0 or 576 Gy

(493 – 716 Gy) γ-irradiation in the 2013 – 14 season. Data in section of treatments are expressed as

mean and standard error of the mean. Data in section of factors general analysis of variance less

than 0.05 mean significantly different. The data at day 0 is not involved in statistical analyses


0 8 12



Hard, no bagging, irradiation 52.60 ± 6.21 56.62 ± 9.60

Hard, bagging, irradiation 33.29 ± 3.5 50.10 ± 5.98

Rubbery, no bagging, no irradiation 39.28 ± 5.09 25.25 ± 4.12 34.9 ± 4.51





Sprung, bagging, no irradiation 31.70 ± 3.53 47.69 ± 2.62



Repeated measurement analysis of variance P value

Irradiation < 0.001


Bagging 0.166

Time 0.015


Irradiation × bagging < 0.001


Irradiation× time 0.016


Bagging × time 0.374



281


Fruit ripeness stage × bagging × time 0.141

Irradiation × fruit ripeness stage × bagging ×

time

0.203

282

Appendices 3.

Table A 3.1 Effects of fruit size (large [12 / tray], medium [14 / tray] and small [16 / tray]) and

storage temperature (6, 10, 13, 16 and 20°C) on AUSB, EUSB and TUSB incidence and severity of

abraded ‗Honey Gold‘ mango fruit when fruit reached eating ripe (n = 12, 14 and 16). ‗Honey

Gold‘ mango fruit of different sizes were harvested from the Northern Territory during the 2011 –

12 season. They were abraded and kept in rooms of different storage temperatures at 90 – 100% RH

for six days. Fruit were finally kept in a ripening room at 20°C and 90 – 100% RH until they

reached eating ripe. Data regarding severity were expressed as the mean and standard error of the

mean. Data regarding incidence were expressed as the mean.

Treatment TUSB AUSB EUSB

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

7°C, large 92 30.02 ± 7.52 92 8 ± 1.64 75 26.91 ± 7.71

7°C, medium 100 26.69 ± 4.23 100 16.3 ± 3.26 79 13.22 ± 3.75

7°C, small 100 34.6 ± 8.11 100 18.42 ± 6.04 75 21.58 ± 2.67

10°C, large 92 43.43 ± 9.8 92 34.51 ± 7.5 75 10.90 ± 4.45

10°C, medium 100 50.72 ± 8.68 100 45.98 ± 7.94 64 7.37 ± 1.74

10°C, small 100 65.4 ± 8.95 100 52.29 ± 8.18 94 13.99 ± 3.69

13°C, large 67 8.8 ± 2.34 67 8.8 ± 2.34 0 0

13°C, medium 79 10.82 ± 3.69 79 10.57 ± 3.6 14 1.37 ± 0.59

13°C, small 100 17.07 ± 6.72 100 15.12 ± 6.05 25 7.83 ± 1.43

16°C, large 100 21.69 ± 7.39 100 20.76 ± 7.41 25 3.71 ± 1.58

16°C, medium 93 21.94 ± 3.69 93 20.63 ± 3.31 14 8.54 ± 3.83

16°C, small 81 37.19 ± 6.4 81 36.97 ± 6.41 6 2.83

20°C, large 33 8.31 ± 3.78 8 7.70 33 6.38 ± 2.16

20°C, medium 21 17.21 ± 9.08 21 14.94 ± 9.22 7 6.83

20°C, small 25 4.48 ± 3.58 19 5.55 ± 4.83 6 1.26

Factors generalized linear model with logistic regression on incidence and conditional factors


P value P value P value P value P value P value

Temperature < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001

Fruit size 0.669 0.317 0.448 0.106 0.584 0.175

283

Temperature ×

fruit size

0.035 0.354 0.063 0.490 0.062 0.293

284

Table A 3.2 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on AUSB,

EUSB and TUSB incidence and severity when fruit reached eating ripe (n = 15). ‗Honey Gold‘

mango fruit harvested from the Northern Territory during the 2012 – 13 season were either abraded

or not, and then kept in rooms at different storage temperatures and 90 – 100% RH for eight days.

Fruit were finally kept in a ripening room at 20°C and 90 – 100% RH until they reached eating ripe.

Data regarding severity were expressed as the mean and standard error of the mean. Data regarding

incidence were expressed as the mean.

TUSB AUSB EUSB

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Non-abrasion,

6°C

40 3.68 ± 0.84 - - 40 3.68 ± 0.84

Abrasion, 6°C 53 6.78 ± 3.48 47 6.09 ± 2.9 27 2.91 ± 1.46

Non-abrasion,

8ºC

47 12.18 ± 4.75 - - 47 12.18 ± 4.75

Abrasion, 8ºC 60 11.87 ± 5.4 53 8.77 ± 3.2 27 9.16 ± 5.11

Non-abrasion,

10°C

27 7.53 ± 3.79 - - 27 7.53 ± 3.79

Abrasion, 10°C 67 19.51 ± 4.69 67 13.51 ± 2.61 53 7.5 ± 2.52

Non-abrasion,

12°C

0 0 - - 0 0

Abrasion, 12°C 60 5.22 ± 1.42 60 4.41 ± 1.22 13 3.67 ± 1.54

Non-abrasion,

20°C

0 0 - - 0 0

Abrasion, 20°C 7 2.74 7 2.74 0 0




Temperature < 0.001 0.691 0.004 0.040 < 0.001 0.217

Abrasion < 0.001 0.024 0.978 0.287

Temperature ×

abrasion

0.039 0.254 0.134 0.885

285

Table A 3.3 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on AUSB,

EUSB and TUSB incidence and severity when fruit reached eating ripe (n = 15). ‗Honey Gold‘

mango fruit harvested from North Queensland during the 2012 – 13 season were either abraded or

not, and then kept in rooms at different storage temperatures and 90 – 100% RH for eight days.

Fruit were finally kept in a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe.

Data regarding severity were expressed as the mean and standard error of the mean. Data regarding

incidence were expressed as the mean.

TUSB AUSB EUSB

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Non-abrasion,

6°C

13 2.82 ± 1.36 - - 13 2.82 ± 1.36

Abrasion, 6°C 27 19.87 ± 8.97 27 15.51 ± 6.67 13 8.72 ± 3.40

Non-abrasion,

8ºC

0 0 - - 0 0

Abrasion, 8ºC 47 11.76 ± 5.25 40 7.43 ± 2.44 13 18.88 ±

17.13

Non-abrasion,

10°C

7 12.66 ± - - - 7 12.66

Abrasion, 10°C 13 33.52 ±

27.94

13 22.13 ±

16.55

7 22.8

Non-abrasion,

12°C

7 11.41 ± - - - 7 11.41

Abrasion, 12°C 13 21.2 ± 14.46 13 21.2 ± 14.46 0 0

Non-abrasion,

20°C

0 0 - - 0 0

Abrasion, 20°C 7 3.85 7 3.85 0 0




Temperature 0.116 0.671 0.161 0.527 - -

Abrasion 0.002 0.168

Temperature × 0.227 0.615

286

abrasion

287

Table A 3.4 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on Fv / Fm of

fruit skin (n = 15). ‗Honey Gold‘ mango fruit grown in the Northern Territory and North

Queensland in the 2012 – 13 season were either abraded or not, and then kept in rooms at different

storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in a ripening room at

20°C and 90 – 100% RH until they reached eating ripe. Data are expressed as the mean.

Fv / Fm Time from abrasion (days)

1 5 8 10 14 1 5 8 14

The Northern Territory North Queensland

20°C, non-

abrasion

0.7733 0.5793 0.4133 0.7853 0.7598 0.6112

20°C, abrasion 0.7549 0.553 0.3355 0.7853 0.6462 0.3653

12°C, non-

abrasion

0.8448 0.7489 0.735 0.7421 0.5337 0.7645 0.7719 0.753 0.5916

12°C, abrasion 0.8372 0.7396 0.7207 0.7181 0.332 0.7657 0.7701 0.7375 0.556

10°C, non-

abrasion

0.8238 0.7388 0.7279 0.747 0.625 0.7671 0.7639 0.739 0.738

10°C, abrasion 0.8326 0.7321 0.7181 0.7442 0.6799 0.7643 0.7632 0.7465 0.7447

8ºC, non-

abrasion

0.7577 0.7615 0.7423 0.7805 0.7851 0.7582 0.7629 0.7306 0.7065

8ºC, abrasion 0.7616 0.74 0.7251 0.7649 0.619 0.7553 0.7575 0.7329 0.7363

6°C, non-

abrasion

0.7777 0.7558 0.7437 0.7761 0.7066 0.7604 0.7753 0.7551 0.7501

6°C, abrasion 0.7673 0.7359 0.736 0.7651 0.7046 0.7605 0.758 0.7492 0.7373

288

Table A 3.5 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on skin colour

of fruit grown in the Northern Territory (n = 15). ‗Honey Gold‘ mango fruit grown in The Northern

Territory in the 2012 – 13 season were either abraded or not, and then kept in rooms at different

storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in a ripening room at

20°C and 90 – 100% RH until they reached eating ripe. Data are expressed as the mean and

standard error of the mean.

Treatments Time from abrasion (days)

0 2 4 6 8 11

Non-abrasion, 6°C 1.1 ± 0.1 1.5 ± 0.1 1.5 ± 0.1 1.6 ± 0.2 1.6 ± 0.2 2.2 ± 0.2

Abrasion, 6°C 1.2 ± 0.1 1.5 ± 0.1 1.6 ± 0.1 1.8 ± 0.2 1.8 ± 0.2 2 ± 0.2

Non-abrasion, 8ºC 1.1 ± 0 1.4 ± 0.1 1.6 ± 0.1 1.6 ± 0.1 1.6 ± 0.1 1.7 ± 0.1

Abrasion, 8ºC 1.1 ± 0 1.5 ± 0.1 1.5 ± 0.1 1.6 ± 0.1 1.7 ± 0.1 2.3 ± 0.2

Non-abrasion, 10°C 1.1 ± 0.1 1.7 ± 0.2 1.8 ± 0.2 1.8 ± 0.2 1.8 ± 0.2 2.9 ± 0.3

Abrasion, 10°C 1.1 ± 0.1 1.4 ± 0.1 1.6 ± 0.1 1.6 ± 0.1 1.6 ± 0.1 2 ± 0.2

Non-abrasion, 12°C 1.2 ± 0.1 1.4 ± 0.2 1.5 ± 0.2 1.6 ± 0.2 1.8 ± 0.3 2.9 ± 0.4

Abrasion, 12°C 1 ± 0 1.8 ± 0.1 1.9 ± 0.1 2.1 ± 0.2 2.6 ± 0.2 4 ± 0.3

Non-abrasion, 20°C 1.1 ± 0.1 2.8 ± 0.2 3.9 ± 0.3 5.1 ± 0.3 5.7 ± 0.1 5.9 ± 0.1

Abrasion, 20°C 1 ± 0 3 ± 0.3 4.4 ± 0.3 5.2 ± 0.2 5.8 ± 0.1 6 ± 0


P value

Temperature < 0.001

Abrasion 0.204

Temperature × abrasion 0.058

Time < 0.001

Time × temperature < 0.001

Time × abrasion 0.326

Time × temperature × abrasion < 0.001

289


of fruit grown in North Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from North

Queensland in the 2012 – 13 season. They were either abraded or not, and then kept in rooms at

different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in ripening

room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are expressed as the mean and

standard error of the mean.


0 4 8 11 14

Non-abrasion, 6°C 1.3 ± 0.2 1.5 ± 0.2 1.5 ± 0.2 1.8 ± 0.2 3.2 ± 0.3

Abrasion, 6°C 1.4 ± 0.1 1.6 ± 0.2 1.6 ± 0.2 1.9 ± 0.2 3.5 ± 0.2

Non-abrasion, 8ºC 1.6 ± 0.2 1.8 ± 0.2 1.9 ± 0.2 2.4 ± 0.3 4 ± 0.4

Abrasion, 8ºC 2.4 ± 0.3 2.4 ± 0.3 2.5 ± 0.3 2.9 ± 0.3 4 ± 0.4

Non-abrasion, 10°C 1.8 ± 0.2 1.9 ± 0.2 1.9 ± 0.2 2.5 ± 0.3 3.9 ± 0.4

Abrasion, 10°C 1.5 ± 0.2 1.6 ± 0.2 1.7 ± 0.2 2.1 ± 0.3 3.3 ± 0.3

Non-abrasion, 12°C 1.5 ± 0.2 1.8 ± 0.2 2 ± 0.2 2.9 ± 0.4 4.2 ± 0.4

Abrasion, 12°C 1.3 ± 0.2 1.6 ± 0.2 2 ± 0.3 2.8 ± 0.4 4 ± 0.4

Non-abrasion, 20°C 1.7 ± 0.2 2.6 ± 0.3 3.6 ± 0.4 4.9 ± 0.4 5.5 ± 0.3

Abrasion, 20°C 1.9 ± 0.2 2.9 ± 0.3 4.2 ± 0.3 5.5 ± 0.2 5.9 ± 0.1


P value

Temperature < 0.001

Abrasion 0.428

Temperature × abrasion < 0.001

Time 0.373



Time × temperature × abrasion 0.770

290


of fruit grown in Southeast Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from

Southeast Queensland in the 2012 – 13 season. Fruit were either abraded or not, and then kept in

rooms at different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in

a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are expressed as the


Treatment Time from abrasion (days)

0 4 8 11 14

Non-abrasion, 6°C 1.3 ± 0.1 1.5 ± 0.1 1.7 ± 0.2 2.7 ± 0.3 4.3 ± 0.3

Abrasion, 6°C 1.2 ± 0.1 1.2 ± 0.1 1.4 ± 0.1 1.9 ± 0.2 4.1 ± 0.3

Non-abrasion, 8ºC 1.5 ± 0.2 1.5 ± 0.2 1.6 ± 0.2 3.1 ± 0.3 4.6 ± 0.3

Abrasion, 8ºC 1.8 ± 0.3 1.8 ± 0.3 1.9 ± 0.3 2.8 ± 0.4 4.6 ± 0.3

Non-abrasion, 10°C 1.8 ± 0.2 1.6 ± 0.2 1.9 ± 0.2 3.2 ± 0.2 5.1 ± 0.2

Abrasion, 10°C 1.1 ± 0.1 1.2 ± 0.1 1.2 ± 0.1 2.2 ± 0.3 3.8 ± 0.3

Non-abrasion, 12°C 1.3 ± 0.2 1.4 ± 0.3 1.6 ± 0.3 3 ± 0.3 4.2 ± 0.3

Abrasion, 12°C 1.4 ± 0.2 1.6 ± 0.2 1.9 ± 0.2 3.1 ± 0.4 4.6 ± 0.3

Non-abrasion, 20°C 1.2 ± 0.1 2.2 ± 0.3 4 ± 0.4 5.6 ± 0.2 6 ± 0

Abrasion, 20°C 2.2 ± 0.3 3.7 ± 0.4 4.3 ± 0.4 5.6 ± 0.2 5.8 ± 0.1


P value

Temperature < 0.001

Abrasion 0.282


Time < 0.001




291

Table A 3.8 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on firmness of

fruit grown in the Northern Territory (n = 15). ‗Honey Gold‘ mango fruit were harvested from the

Northern Territory in the 2012 – 13 season. Fruit were either abraded or not, and then kept in rooms

at different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in a

ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Data are expressed as the



0 2 4 6 8 11

Non-abrasion, 6°C 0 ± 0 0.1 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 0.3 ± 0.1

Abrasion, 6°C 0 ± 0 0 ± 0 0 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.2 ± 0.1

Non-abrasion, 8ºC 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0.3 ± 0.1

Abrasion, 8ºC 0 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 0.4 ± 0.1

Non-abrasion, 10°C 0 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 0.7 ± 0.1

Abrasion, 10°C 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0.6 ± 0.1

Non-abrasion, 12°C 0 ± 0 0 ± 0 0 ± 0 0.1 ± 0.1 0.3 ± 0.1 0.9 ± 0.2

Abrasion, 12°C 0 ± 0 0.1 ± 0 0.1 ± 0 0.1 ± 0.1 0.4 ± 0.1 1.4 ± 0.2

Non-abrasion, 20°C 0 ± 0 0.9 ± 0.1 1.3 ± 0.1 2 ± 0.1 2.7 ± 0.1 4 ± 0

Abrasion, 20°C 0 ± 0 1 ± 0.1 1.5 ± 0.2 2 ± 0.2 3 ± 0.2 3.9 ± 0.1


P value

Temperature < 0.001

Abrasion 0.379

Temperature × Abrasion 0.393

Time < 0.001

Time × Temperature < 0.001

Time × Abrasion 0.213

Time × Temperature × Abrasion 0.036

292

Table A 3.9 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on firmness

of fruit grown in North Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from

North Queensland in the 2012 – 13 season. Fruit were either abraded or not, and then kept in

rooms at different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept

in a ripening room at 20°C and 90 – 100% RH until they reached eating ripe. Data are expressed

as the mean and standard error of the mean.


0 4 8 11 14

Non-abrasion, 6°C 0 ± 0 0 ± 0 0 ± 0 0.2 ± 0.1 1.9 ± 0.1

Abrasion, 6°C 0.1 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.3 ± 0.1 1.8 ± 0.1

Non-abrasion, 8ºC 0.2 ± 0.1 0.2 ± 0.1 0.2 ± 0.1 0.3 ± 0.1 1.6 ± 0.2

Abrasion, 8ºC 0 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.3 ± 0.1 1.7 ± 0.2

Non-abrasion, 10°C 0.1 ± 0.1 0.2 ± 0.1 0.2 ± 0.1 0.8 ± 0.2 2 ± 0.2

Abrasion, 10°C 0 ± 0 0.1 ± 0.1 0.2 ± 0.1 0.4 ± 0.1 2 ± 0.2

Non-abrasion, 12°C 0 ± 0 0.1 ± 0.1 0.2 ± 0.1 0.4 ± 0.1 2.3 ± 0.2

Abrasion, 12°C 0 ± 0 0.2 ± 0.1 0.2 ± 0.1 0.7 ± 0.1 2.5 ± 0.1

Non-abrasion, 20°C 0.1 ± 0.1 0.3 ± 0.1 1.3 ± 0.3 1.9 ± 0.3 3.3 ± 0.3

Abrasion, 20°C 0.1 ± 0.1 0.5 ± 0.2 1.7 ± 0.2 2.7 ± 0.2 3.7 ± 0.1


P value

Temperature < 0.001

Abrasion 0.179


Time < 0.001




293

Table A 3.10 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on firmness

of fruit grown in Southeast Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from


rooms at different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept

in a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are expressed as

the mean and standard error of the mean.

Treatments Time from abrasion test (days)

0 4 8 11 14

Non-abrasion, 6°C 0.1 ± 0.1 0.1 ± 0.1 0.2 ± 0.1 1.2 ± 0.2 2.5 ± 0.2

Abrasion, 6°C 0.1 ± 0.1 0 ± 0 0.1 ± 0.1 0.7 ± 0.2 2.3 ± 0.2

Non-abrasion, 8ºC 0.1 ± 0.1 0.1 ± 0.1 0.2 ± 0.1 1.2 ± 0.3 3 ± 0.2

Abrasion, 8ºC 0.1 ± 0 0.1 ± 0.1 0.1 ± 0.1 0.7 ± 0.2 2.1 ± 0.2

Non-abrasion, 10°C 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 1.3 ± 0.2 3.2 ± 0.2

Abrasion, 10°C 0 ± 0 0 ± 0 0 ± 0 0.8 ± 0.2 2.8 ± 0.4

Non-abrasion, 12°C 0.1 ± 0.1 0.1 ± 0.1 0.1 ± 0.1 1 ± 0.2 2.8 ± 0.2

Abrasion, 12°C 0.2 ± 0.1 0.3 ± 0.2 0.3 ± 0.2 1.3 ± 0.3 3.2 ± 0.1

Non-abrasion, 20°C 0 ± 0 0.8 ± 0.2 1.6 ± 0.2 2.7 ± 0.2 3.7 ± 0.1

Abrasion, 20°C 0.3 ± 0.1 1 ± 0.3 2.1 ± 0.2 2.9 ± 0.2 3.8 ± 0.1


P value

Temperature < 0.001

Abrasion 0.981


Time < 0.001


Time × abrasion < 0.001


294

Table A 3.11 Effects of abrasion test and storage temperature (6, 8, 10, 12 and 20°C) on weight loss

of fruit grown in the Northern Territory (n = 15). ‗Honey Gold‘ mango fruit were harvested from

The Northern Territory in the 2012 – 13 season. Fruit were either abraded or not, and then kept in





2 4 8 11

Non-abrasion, 6°C 0.43 ± 0.02 0.63 ± 0.03 0.79 ± 0.03 1.64 ± 0.06

Abrasion, 6°C 0.52 ± 0.04 0.89 ± 0.03 1.15 ± 0.03 2.15 ± 0.03

Non-abrasion, 8ºC 0.46 ± 0.02 0.8 ± 0.04 1.06 ± 0.05 1.9 ± 0.09

Abrasion, 8ºC 0.62 ± 0.01 1.08 ± 0.03 1.43 ± 0.03 5.71 ± 3.21

Non-abrasion, 10°C 0.49 ± 0.02 0.73 ± 0.05 1.01 ± 0.03 1.9 ± 0.06

Abrasion, 10°C 0.51 ± 0.02 0.98 ± 0.03 1.37 ± 0.04 2.56 ± 0.09

Non-abrasion, 12°C 0.51 ± 0.02 0.89 ± 0.04 1.24 ± 0.03 1.99 ± 0.05

Abrasion, 12°C 0.55 ± 0.01 1.09 ± 0.03 1.61 ± 0.03 2.7 ± 0.06

Non-abrasion, 20°C 0.76 ± 0.02 1.38 ± 0.03 2.66 ± 0.05 3.4 ± 0.07

Abrasion, 20°C 0.85 ± 0.02 1.77 ± 0.03 3.2 ± 0.09 4.1 ± 0.11


P value

Temperature < 0.001

Abrasion 0.002


Time < 0.001

Time × temperature 0.189



295


fruit grown in North Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from North

Queensland in the 2012 – 13 season. Fruit were either abraded or not, and then kept in rooms at

different storage temperatures and 90 – 100% RH for eight days. Fruit were finally kept in a

ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Data are expressed as the


Treatments Time from abrastion test (days)

4 8 11 14

Non-abrasion, 6°C 0.35 ± 0.01 0.5 ± 0.02 1.29 ± 0.04 2.42 ± 0.09

Abrasion, 6°C 0.58 ± 0.02 0.79 ± 0.04 1.81 ± 0.08 3.24 ± 0.13

Non-abrasion, 8ºC 0.45 ± 0.02 0.57 ± 0.02 1.4 ± 0.22 2.41 ± 0.25

Abrasion, 8ºC 0.6 ± 0.02 0.78 ± 0.02 1.61 ± 0.05 2.93 ± 0.09

Non-abrasion, 10°C 0.77 ± 0.03 1.54 ± 0.42 1.85 ± 0.07 2.96 ± 0.1

Abrasion, 10°C 1.1 ± 0.04 1.55 ± 0.05 2.44 ± 0.08 3.86 ± 0.13

Non-abrasion, 12°C 0.61 ± 0.01 0.88 ± 0.02 1.6 ± 0.04 2.65 ± 0.07

Abrasion, 12°C 1 ± 0.03 1.46 ± 0.11 2.95 ± 0.38 4.03 ± 0.16

Non-abrasion, 20°C 1.23 ± 0.05 1.91 ± 0.08 2.75 ± 0.11 3.48 ± 0.13

Abrasion, 20°C 1.81 ± 0.04 2.73 ± 0.06 3.85 ± 0.07 4.78 ± 0.08


P value

Temperature < 0.001

Abrasion < 0.001

Temperature ×

Abrasion

< 0.001

Time < 0.001


Time × abrasion < 0.001


296


fruit grown in Southeast Queensland (n = 15). ‗Honey Gold‘ mango fruit were harvested from






8 11 14

Non-abrasion, 6°C 0.76 ± 0.03 1.56 ± 0.06 2.62 ± 0.1

Abrasion, 6°C 1.07 ± 0.06 1.98 ± 0.08 3.21 ± 0.12

Non-abrasion, 8ºC 0.85 ± 0.03 1.66 ± 0.06 2.74 ± 0.08

Abrasion, 8ºC 0.94 ± 0.05 8.38 ± 6.55 9.44 ± 6.47

Non-abrasion, 10°C 1.22 ± 0.05 2.06 ± 0.08 3.06 ± 0.11

Abrasion, 10°C 1.55 ± 0.04 2.48 ± 0.07 3.62 ± 0.09

Non-abrasion, 12°C 1.44 ± 0.06 2.3 ± 0.08 1.6 ± 1.7

Abrasion, 12°C 1.86 ± 0.07 2.84 ± 0.1 4.04 ± 0.13

Non-abrasion, 20°C 2.47 ± 0.1 3.28 ± 0.12 4.01 ± 0.13

Abrasion, 20°C 3.6 ± 0.1 4.69 ± 0.11 5.73 ± 0.12


P value

Temperature < 0.001

Abrasion < 0.001

Temperature × Abrasion < 0.001

Time < 0.001

Time × Temperature < 0.001

Time × Abrasion < 0.001

Time × Temperature × Abrasion < 0.001

297

Table A 3.14 Effects of temperature (1 – 28ºC) on the ratio of Fv and Fm of skin disc of mango fruit

grown in the Northern Territory and North Queensland (n = 3). ‗Honey Gold‘ mango fruit were

harvested from either the Northern Territory or North Queensland. Fruit skin discs were treated

with different temperatures on a thermal gradient block. Data are expressed as mean.

Temperature

(oC)

Time (days)

The Northern

Territory

North Queensland

Rep 1 Rep 1 Rep 2

1 6 1 3 6 8 1 2

1.15 0.747 0.7 0.7687 0.771 0.7443 0.5257 0.783 0.757

2.05 0.7453 0.671 0.779 0.7937 0.739 0.447 0.7803 0.741

3.35 0.752 0.614 0.7663 0.7553 0.723 0.5927 0.7733 0.733

4.55 0.739 0.62 0.7567 0.744 0.7363 0.5497 0.7797 0.7617

5.75 0.7283 0.601 0.7643 0.7547 0.7233 0.6307 0.7757 0.7497

7 0.747 0.62 0.7677 0.754 0.711 0.412 0.7567 0.7243

8.05 0.7457 0.597 0.759 0.7723 0.6587 0.6103 0.7433 0.718

9.35 0.747 0.589 0.764 0.7757 0.724 0.5303 0.7797 0.7457

10.65 0.7487 0.599 0.7583 0.7797 0.715 0.463 0.7733 0.749

11.8 0.721 0.586 0.7573 0.778 0.7177 0.6747 0.7697 0.736

12.95 0.7183 0.577 0.7517 0.7827 0.7297 0.544 0.7467 0.7163

14.05 0.742 0.579 0.739 0.7767 0.6383 0.4257 0.7723 0.7383

15.35 0.7563 0.593 0.7443 0.762 0.725 0.622 0.7663 0.723

16.6 0.7017 0.583 0.7483 0.735 0.5187 0.5047 0.7697 0.7147

17.75 0.736 0.584 0.745 0.753 0.67 0.5317 0.7797 0.7313

19 0.7317 0.567 0.712 0.7463 0.5603 0.4653 0.7653 0.712

20.35 0.7467 0.552 0.725 0.715 0.6937 0.4557 0.763 0.7427

21.45 0.7307 0.571 0.7497 0.6877 0.6797 0.3707 0.7747 0.748

Factors analysis of variance Factors repeated measurement

analysis of variance

Factors analysis of

variance

P

value

P value P value P

value

Temperature 0.200 0.999 Temperature 0.064 Temperature

Time < 0.001 0.648 0.183

Time × Temperature 0.671

298

Table A 3.15 Effects of fruit size (large [12 / tray], medium [14 / tray] and small [16 / tray]) and

storage duration (1, 3, 6 and 9 days) at 13°C on the incidence and severity of AUSB, EUSB and

TUSB of abraded fruit (n = 12, 14 and 16). ‗Honey Gold‘ mango fruit of different sizes were

harvested from the Northern Territory in the 2011-12 season. Fruit were abraded, kept in a cold

room at 13°C and 90 – 100% RH for different storage durations and moved to a ripening room at

20°C and 90 – 100% RH until fruit reached eating ripe. Data regarding severity were expressed as

the mean and standard error of the mean. Data regarding incidence were expressed as the mean.

Treatments TUSB AUSB EUSB

Incidence Severity (cm2

affected)


affected)


affected)

1, large 67 15.34 ± 3.27 67 8.8 ± 2.34 0 0

1, medium 79 13.64 ± 3.85 79 10.57 ± 3.6 14 1.37 ± 0.59

1, small 100 20.75 ± 7.07 100 15.12 ± 6.05 25 7.83 ± 1.43

3, large 100 30.75 ± 4.83 100 19.69 ± 3.8 50 4.87 ± 1.25

3, medium 93 35.28 ± 4.39 93 26.78 ± 4.49 21 7.51 ± 5.72

3, small 88 34.11 ± 5.35 88 28.94 ± 5.34 25 4.02 ± 1.89

6, large 100 56.94 ± 6.06 92 44.65 ± 5.68 50 20 ± 6.57

6, medium 100 44.87 ± 5.49 100 35.97 ± 4.58 50 9.32 ± 3.02

6, small 88 48.9 ± 6.64 88 45.42 ± 6.54 6 3.46 ± *

9, large 92 57.12 ± 9.16 92 50.32 ± 9.26 25 8.41 ± 1.46

9, medium 100 60.65 ± 8.4 93 52.38 ± 6.7 57 12.29 ± 3.56

9, small 100 55.41 ± 8.94 100 47.41 ± 8.93 50 9.12 ± 1.73




Duration 0.089 < 0.001 0.268 < 0.001 0.017 0.035

Fruit size 0.701 0.833 0.512 0.758 0.536 0.333

Duration ×

fruit size

0.012 0.889 0.033 0.787 0.003 0.229

299

Table A 3.16 Effects of delayed cooling fruit at day 0, 1, 2 and 4 on incidence and severity of

TUSB, AUSB and EUSB (n = 5). ‗Honey Gold‘ fruit were harvested from North Queensland.

Fruit were kept in a ripening room at 20°C for zero, one, two and four days. After abrasion, fruit

were kept in a cold room at 13°C and 90 – 100% RH for six more days. Fruit were finally moved

to a ripening room at 20°C and 90 – 100% RH until fruit reached eating ripe. Fruit without

abrasion kept at 13°C for six days were the controls. Data regarding severity were expressed as

the mean and standard error of the mean. Data regarding incidence were expressed as the mean.


Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

Incidence Severity

(cm2

affected)

13°C, non-

abrasion

13 2.29 ± 1.268 13 2.29 ± 1.27 0 0

0 27 6.99 ± 1.58 27 6.64 ± 1.46 7 1.38

1 33 9.47 ± 2.1 33 9.10 ± 2.29 7 1.89

2 20 3.09 ± 1.06 13 2.67 ± 1.69 7 3.93

4 20 1.96 ± 0.67 20 1.96 ± 0.67 0 0




Treatment 0.738 0.014 0.612 0.025 0.533 0.738

300

Table A 3.17 Effects of delaying abrasion test on the incidence and severity of AUSB, EUSB and

TUSB (n = 15). ‗Honey Gold‘ mango fruit were harvested from North Queensland during the 2011-

12 season. Fruit were initially kept in a cold room at 13°C and RH = 90 – 100% firstly and then

abraded on different days. The fruit were then kept in a cold room at 13°C and RH = 90 – 100% for

six more days, and finally kept in a ripening room at 20°C and RH = 90- 100% until fruit reached

eating ripe. Data regarding severity were expressed as mean and standard error of the mean. Data

regarding incidence were expressed as mean.



affected)


affected)


affected)

20°C, non-

abrasion

13 2.29 ± 1.268 13 2.29 ± 1.27 0 0

0 27 6.99 ± 1.581 27 6.64 ± 1.46 7 1.382

1 60 11.5 ± 5.467 60 11.50 ± 5.47 0 0

2 20 13.79 ±

2.791

20 13.79 ± 2.79 0 0

4 27 17.19 ±

1.967

27 17.19 ± 1.97 0 0

6 20 8.25 ± 3.254 20 8.25 ± 3.25 0 0




Treatment 0.089 0.175 0.089 0.602 - -

301

Appendices 4.

A B

C D

E F

302

Figure A 4.1 Transverse sections with O-toluidine blue stain through ‗Honey Gold‘ mango fruit

skin affected with no USB (A [× 4], B [× 10]), skin affected with USB (C [× 4], D [× 10]), skin

affected with severe skin browning caused by terpinolene (E [× 4], F [× 10]), skin affected with

severe brownign caused by spurt sap (G [× 4], H [× 10]) and skin affected with mild skin browning

(I [× 4], J [× 10]). Bars 100 μm (A, C, E, G and I) and 50 μm (B, D, F, H and J). Ep: epidermal

cells; Sp: sub-epidermal cells; RD: resin duct; USB: under-skin browning; SB: severe skin

browning. MB: mild skin browning.

G H

I J

303

Table A 4.1 Effects on total skin browning incidence (%) and severity (cm2 affected) of ‗Honey

Gold‘ mango fruit treated with sap sample and kept at 12 and 20°C (n = 3 [4 sub-samples per

fruit]). The fruit were harvested from Northern Territory in 2013 – 14 season. Different sap sample

of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl

terpinolene and 100 µl distilled water were applied to small areas of the fruit abraded with sand

paper or peeled with peeler or cutted with a scalpel. Fruit were then held in either 12 or 20°C at 90

– 100% RH for eight days. Data for severity and incidence are expressed as mean and standard error

of the mean. Data of distilled water and morning ooze sap treatments for any damage type were not

involved in statistical analyses on incidence and severity.

Total skin browning

Incidence (%) Severity (cm2

affected)

12°C 20°C 12°C 20°C

Abraded

100 µl Distilled water 0 0 0 0

50 µl Terpinolene 100 ± 0 92 ± 8 13.52 ±

3.12

8.58 ± 1.36

100 µl Morning spurt sap 92 ± 8 58 ± 22 5.3 ± 0.85 1.95 ± 0.56

100 µl Afternoon spurt sap 100 ± 0 92 ± 8 2.81 ± 0.23 2.78 ± 0.52

100 µl Morning ooze sap 0 0 0 0

100 µl Afternoon ooze sap 0 0 0 0

100 µl Upper-phase morning spurt sap 100 ± 0 100 ± 0 6.36 ± 0.71 6.16 ± 0.65

100 µl Upper-phase afternoon spurt sap 92 ± 8 100 ± 0 6.13 ± 1.11 9.81 ± 0.2

Cutting


50 µl Terpinolene 100 ± 0 100 ± 0 10.19 ±

0.19

9.34 ± 0.82

100 µl Morning spurt sap 50 ± 29 17 ± 17 2.36 ± 0.92 1.99


100 µl Morning ooze sap 0 0 0 0

100 µl Afternoon ooze sap 75 ± 14 17 ± 17 2.51 ± 0.8 1.48

100 µl Upper-phase morning spurt sap 92 ± 8 33 ± 33 8.61 ± 1.15 4.35

100 µl Upper-phase afternoon spurt sap 100 ± 0 100 ± 0 11.89 ±

0.43

6.98 ± 1.3

Peeled

304


50 µl Terpinolene 100 ± 0 100 ± 0 7.34 ± 0.51 7.24 ± 0.76



100 µl Morning ooze sap - - - -

100 µl Afternoon ooze sap - - - -

100 µl Upper-phase morning spurt sap - - - -

100 µl Upper-phase afternoon spurt sap 100 ± 0 100 ± 0 8.65 ± 1.23 9.6 ± 0.93

Unbalanced generalised linear model under the binomial distribution

and logit link

Conditional ANOVA

P value P value

Damage type 0.147 0.787

Storage temperature 0.006 < 0.001

Sap sample < 0.001 0.015

Damage type × storage temperature 0.083 0.002

Damage type × Sap sample < 0.001 0.228

Storage temperature × Sap sample 0.396 0.675

Damage type × storage temperature × Sap

sample

0.993 0.001

305

Table A 4.2 Effects on severe skin browning incidence (%) and severity (cm2 affected) of ‗Honey


fruit]). The fruit were harvested from Northern Territory in the 2013 – 14 season. Different sap

sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl




of the mean. Data of distilled water and morning ooze sap treatments for any damage type were not

involved in statistical analyses on incidence and severity.

Treatments Severe skin browning


affected)

12°C 20°C 12°C 20°C

Abraded

100 µl Distilled water 0 ± 0 0 ± 0 0 ± 0 0 ± 0

50 µl Terpinolene 100 ± 0 100 ± 0 12.44 ± 2.11 8.04 ± 1.17

100 µl Morning spurt sap 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Afternoon spurt sap 100 ± 0 42 ± 22 3 ± 0.69 1.02 ± 0.3

100 µl Morning ooze sap 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Afternoon ooze sap 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Upper-phase morning

spurt sap

83 ± 8 92 ± 8 4.14 ± 0.39 4.39 ± 0.24

100 µl Upper-phase afternoon

spurt sap

83 ± 8 92 ± 8 3.55 ± 0.6 5.65 ± 1.32

Cutting


50 µl Terpinolene 100 ± 0 100 ± 0 11.75 ± 2.22 8.11 ± 1.31

100 µl Morning spurt sap 42 ± 30 0 ± 0 1.16 ± 0.66 0 ± 0



100 µl Afternoon ooze sap 50 ± 14 0 ± 0 1.58 ± 0.74 0 ± 0


spurt sap

92 ± 8 33 ± 33 5.35 ± 1.07 3.79


spurt sap

100 ± 0 100 ± 0 8.01 ± 0.82 5.65 ± 1.17

306

Peeled


50 µl Terpinolene 100 ± 0 100 ± 0 7.77 ± 1.21 7.16 ± 0.9

100 µl Morning spurt sap 0 ± 0 0 ± 0 0 ± 0 0 ± 0





spurt sap

- - - -


spurt sap

100 92 ± 8 5.41 ± 0.8 8.28 ± 0.29

Unbalanced generalised linear model under the binomial

distribution and logit link

Conditional ANOVA

P value P value

Damage type < 0.001 0.533

Storage temperature < 0.001 < 0.001

Sap sample < 0.001 0.034

Damage type × storage

temperature

0.029 0.044

Damage type × Sap sample 0.002 0.258


Damage type × storage

temperature × Sap sample

0.059 0.142

307

Table A 4.3 Effects on mild skin browning incidence (%) and severity (cm2 affected) of ‗Honey


fruit]). The fruit were harvested from Northern Territory in the 2013 – 14 season. Different sap

sample of 100 µl aliquots of morning and afternoon spurt sap, 100 µl of their upper-phase, 50 µl




of the mean. The data of distilled water and morning ooze sap treatments for any damage type were

not involved in statistical analyses on incidence and severity.

Mild skin browning


affected)

12°C 20°C 12°C 20°C

Abraded


50 µl Terpinolene 100 ± 0 75 ± 0 2.04 ± 0.38 1.45 ± 0.52




100 µl Afternoon ooze sap 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Upper-phase morning spurt sap 100 ± 0 92 ± 8 2.79 ± 0.35 2.24 ± 0.21

100 µl Upper-phase afternoon spurt

sap

92 ± 8 100 ± 0 2.58 ± 0.61 2.34 ± 0.49

Cutting


50 µl Terpinolene 100 ± 0 67 ± 22 1.43 ± 0.31 1.69 ± 0.31

100 µl Morning spurt sap 50 ± 29 17 ± 17 1.38 ± 0.19 1.99



100 µl Afternoon ooze sap 75 ± 14 17 ± 17 1.56 ± 0.28 1.48

100 µl Upper-phase morning spurt sap 92 ± 8 33 ± 33 3.31 ± 0.32 2.75


sap

100 ± 0 83 ± 17 3.25 ± 0.29 2.68 ± 0.61

Peeled


308

50 µl Terpinolene 92 ± 8 58 ± 22 1.7 ± 0.31 1.32 ± 0.25





100 µl Upper-phase morning spurt sap - - - -


sap

92 ± 8 83 ± 8 3.59 ± 0.80 4.40 ± 1.20

Unbalanced generalised linear model under the binomial

distribution and logit link

Conditional ANOVA

P value P value

Damage type 0.524 0.873

Storage temperature < 0.001 < 0.001

Sap sample < 0.001 < 0.001

Damage type × storage temperature 0.144 0.057

Damage type × Sap sample 0.013 0.391


Damage type × storage temperature ×

Sap sample

0.797 0.164

309

Table A 4.4 Effects of storage temperature on incidence (%) of mild, severe and total skin browning of abraded fruit (n = 3 [4 sub-samples per fruit] / 3

[1 sub-replicate per fruit]). The fruit treated with 0.1 ml upper-phase morning and afternoon spurt sap were not involved in statistical analyses because

of few data. ‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2014 – 15 season. Different sap components of 0.1 ml (morning

and afternoon spurt sap, upper-phase morning and afternoon spurt sap, morning and afternoon ooze sap, terpinolene and distilled water) was applied to

small areas of the fruit that were abraded with sand paper or peeled with peeler or cutted with scalpel. Fruit were then kept in 12 or 20°C at 90 – 100%

RH for eight days. Data for severity and incidence are expressed as mean and standard error of the mean. The data of the treatment of distilled water

were not involved in statistical analyses.

Incidence

Treatment Mild skin browning Severe skin browning Total skin browning

12°C 20°C 12°C 20°C 12°C 20°C

100 µl Distilled water 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Terpinolene 58 ± 22 42 ± 22 100 ± 0 100 ± 0 100 ± 0 100 ± 0

100 µl Morning spurt sap 20 ± 14 0 ± 0 0 ± 0 0 ± 0 50 ± 14 0 ± 0

100 µl Afternoon spurt sap 67 ± 8 0 ± 0 8 ± 8 0 ± 0 67 ± 8 0 ± 0

100 µl Upper-phase morning spurt sap 100 ± 0 100 ± 0 67 ± 33 33 ± 33 100 ± 0 100 ± 0

100 µl Upper-phase afternoon spurt sap 100 ± 0 100 ± 0 100 ± 0 100 ± 0 100 ± 0 100 ± 0


Storage temperature < 0.001 0.657 0.002

Sap sample < 0.001 < 0.001 < 0.001

Storage temperature × Sap sample 0.060 0.984 -

310

Table A 4.5 Effects of storage temperature on severity (cm2 affected) of mild, severe and total skin browning of abraded fruit (n = 3 [4 sub-samples per

fruit] / 3 [1 sub-replicate per fruit]). The fruit treated with 0.1 ml upper-phase morning and afternoon spurt sap were not involved in statistical analyses

because of few data. ‗Honey Gold‘ mango fruit were harvested from Northern Territory. Different sap components of 0.1 ml (morning and afternoon

spurt sap, upper-phase morning and afternoon spurt sap, morning and afternoon ooze sap, terpinolene and distilled water) was applied to small areas of

the fruit that were abraded with sand paper or peeled with peeler or cutted with scalpel. Fruit were then kept in 12 or 20°C at 90 – 100% RH for eight

days. Data for severity and incidence are expressed as mean and standard error of the mean. The data of the treatment of distilled water were not

involved in statistical analyses.

Treatment Severity (cm2 affected)

Mild skin browning Severe skin browning Total skin browning

12°C 20°C 12°C 20°C 12°C 20°C

100 µl Distilled water 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0 0 ± 0

100 µl Terpinolene 4.79 ± 0.78 1.29 ± 0.37 23.32 ± 1.74 23.80 ± 2.87 26.15 ± 0.97 24.66 ± 3.26

100 µl Morning spurt sap 1.58 ± 0.71 0 ± 0 0 ± 0 0 ± 0 1.58 ± 0.72 0 ± 0

100 µl Afternoon spurt sap 1.82 ± 0.36 0 ± 0 0.08 0 ± 0 1.82 ± 0.36 0 ± 0

100 µl Upper-phase morning spurt sap 2.85 ± 1.24 1.09 ± 0.42 2.67 ± 0.86 0.50 4.63 ± 2.26 1.25 ± 0.55

100 µl Upper-phase afternoon spurt sap 7.42 ± 1.05 7.24 ± 1.56 6.30 ± 2.07 3.85 ± 0.39 13.72 ± 1.85 11.09 ± 1.92


Storage temperature 0.401 0.049 0.065

Sap sample < 0.001 < 0.001 < 0.001

Storage temperature × Sap sample 0.683 0.278 0.848

311

Table A 4.6 Effect on incidence (%) and severity (cm2 affected) of severe skin browning of the

abraded position treated with different volumes of terpinolene kept in 12°C and 20°C (n = 3 [4 sub-

samples per fruit]). ‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2013 –

14 season. Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl terpinolene, and


with peeler or cutted with scalpel. All fruit were then kept in different room (12 and 20°C, RH = 90

– 100%) for eight days. Data for severity and incidence are expressed as mean and standard error of

the mean. The data of the treatment of distilled water and terpinolene of 6.3 and 3.1μl were not

involved in statistical analyses.


Incidence (%) Severity (cm2 affected)

12°C 20°C 12°C 20°C

100μl distilled water 0 0

0.00 0.00

100μl terpinolene 100 100 17.38 ± 1.50 16.43 ± 0.90

50μl terpinolene 100 100 6.09 ± .37 9.41 ± 0.94

25μl terpinolene 92 ± 8 92 2.23 ± 0.14 2.39 ± 0.80

12.5μl terpinolene 67 ± 33 50 0.32 ± 0.12 0.54 ± 0. 2

6.3μl terpinolene 0 0 0.00 0.00

3.1μl terpinolene 0 0 0.00 0.00

P value P value

Storage temperature 0.295 0.868

Volume < 0 001 < 0.001

Storage temperature × volume 0.144 0.012

312

Table A 4.7 Effect on mild skin browning incidence (%) and severity (cm2 affected) of the abraded

position treated with different volumes of terpinolene kept in 12°C and 20°C (n = 3 [4 sub-samples

per fruit]). ‗Honey Gold‘ mango fruit were harvested from Northern Territory in the 2013 – 14

season. Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl terpinolene, and distilled

water) were applied to small areas of the fruit that were abraded with sand paper or peeled with

peeler or cutted with scalpel. All fruit were then kept in different room (12 and 20°C, RH = 90 –

100%) for eight days. Data for severity and incidence are expressed as mean and standard error of

the mean. The data of the treatment of distilled water were not involved in statistical analyses.

Mild skin browning


Amounts of terpinolene 12°C 20°C 12°C 20°C

100μl distilled water 0 0 0 0

100μl terpinolene 100 100 3.57 ± 0.73 2.68 ± 0.44

50μl terpinolene 100 100 3.04 ± 0.16 3.21 ± 0.55

25μl terpinolene 100 100 3.93 ± 0.28 3.90 ± 0.54

12.5μl terpinolene 100 100 4.70 ± 0.13 4.66 ± 0.23

6.3μl terpinolene 67 33 92 ± 8 4.00 ± 0.67 2.86 ± 0.23

3.1μl terpinolene 83 ± 8 67 ± 33 2.10 ± 0.28 1.85 ± 0.17

P value P value


Volume < 0.001 < 0.001


313

Table A 4.8 Effect on total skin browning incidence (%) and severity (cm2 affected) of the abraded

position treated with different volumes of terpinolene kept in 12°C and 20°C (n = 3 individual fruit

replicates and 4 sub-samples per fruit). ‗Honey Gold‘ mango fruit were harvested from Northern

Territory. Different volumes of terpinolene (3.1, 6.3, 12.5, 25, 50 and 100 μl terpinolene, and


with peeler or cutted with scalpel. All fruit were then kept in different room (12 and 20°C, RH = 90

– 100%) for eight days. Data for severity and incidence are expressed as mean and standard error of

the mean. The data of the treatment of distilled water were not involved in statistical analyses.

Total skin browning


Treatments 12°C 20°C 12°C 20°C

100μl Distilled water 0 0 0 0

100μl Terpinolene 100 100 20.07 ± 1.76 17.26 ± 0.79

50μl Terpinolene 100 100 10.73 ± 1.91 11.26 ± 0.71

25μl Terpinolene 100 100 6.24 ± 0.31 5.85 ± 0.38

12.5μl Terpinolene 100 100 4.94 ± 0.24 5.07 ± 0.30

6.3μl Terpinolene 67 ± 33 92 ± 8 4.00 ± 0.67 2.86 ± 0.23

3.1μl Terpinolene 83 ± 8 67 ± 33 2.10 ± 0.28 1.85 ± 0.17

P value P value


Volume < 0.001 < 0.001


lenticel discolouration on ‘b74’ mango fruit and374759/s4269501_phd_submission.pdfthe award of...

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