UNIVERSITI PUTRA MALAYSIA

POSTHARVEST QUALITY OF RED PITAYA (Hylocereus polyrhizus) AS AFFECTED BY HARVEST DATE, STORAGE DURATION AND 1-

METHYLCYCLOPROPENE

MELLY NOVITA

FP 2008 4

POSTHARVEST QUALITY OF RED PITAYA (Hylocereus polyrhizus) AS AFFECTED BY HARVEST DATE, STORAGE DURATION

AND 1-METHYLCYCLOPROPENE

MELLY NOVITA

MASTER OF SCIENCE UNIVERSITI PUTRA MALAYSIA

2008

POSTHARVEST QUALITY OF RED PITAYA (Hylocereus polyrhizus) AS AFFECTED BY HARVEST DATE, STORAGE DURATION AND

1-METHYLCYCLOPROPENE

By

MELLY NOVITA

Thesis submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of

Master of Science

March 2008

This thesis is especially dedicated to my beloved:

Bunda Cut Dian Faridah,……

Cut bang Hery, Cut anda Ira, Bang Yan and my love

For love, sacrifices and support

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Master of Science

POSTHARVEST QUALITY OF RED PITAYA (Hylocereus polyrhizus) AS AFFECTED BY HARVEST DATE, STORAGE DURATION AND

1-METHYLCYCLOPROPENE

By

MELLY NOVITA

April 2008

Chairman : Associate Professor Siti Hajar Ahmad, PhD

Faculty : Agriculture

Pitaya is a non-climacteric fruit, so it has to be harvested at the optimum edible

stage of maturity. The maturity at harvest greatly influences the eating quality

and storage life of fruits. Storage of pitaya more than 7 days at ambient

temperature causes scales shriveling and degreening, and peel and pulp softening

resulting in reduced quality. Little information is available on optimum harvest

date and storage method for pitaya. In this study, the first experiment was to

determine harvest date using growth and physico-chemical changes of red pitaya

up to 40 days after anthesis (DAA). When fruit growth, as indicated by increment

in diameter, length and weight, remained constant from 25 to 40 DAA, physico-

chemical changes started to occur. Peel and pulp turned vivid purple followed by

decreased firmness, acidity and ascorbic acid content of pulp while soluble solids

concentration and pH increased.

The second experiment was carried out to determine the effects of harvest date

and 1-MCP during 28 days of storage on physico-chemical changes of red pitaya.

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Fruits were harvested at 30 and 35 DAA and treated with 0, 250, 500, 750 and

1000 nL/L 1-MCP for 4 h at ambient temperature and then stored for 28 days at

10 oC. There were linear increases in water loss but linear decreases in pulp

firmness of both 30 and 35 DAA harvested fruits during 28 days of storage. L*

and C* colour values of fruits from both harvest dates changed to produce vivid

purple peel during the storage period. Fruits harvested at 30 DAA had slower

increase in sugar:acid and pH during storage compared to fruits harvested at 35

DAA. Ascorbic acid and betacyanin content of fruits harvested at 35 DAA

showed decreasing quadratic trend during storage, while phenolic content had a

linear decrease. Fruits harvested at 35 DAA had linear increases in ascorbic acid

and phenolic content when treated with increasing 1-MCP concentration, while

betacyanin content had a quadratic increase during 28 days of storage. Fruits

harvested at 30 DAA had 33% more CO2 at 0 day of storage compared to fruits

harvested at 35 DAA. However, the trend of quadratic decrease in CO2

production during storage duration in both harvested fruits was similar. There

were no interaction effects of storage duration and 1-MCP on ethylene and CO2

production of fruit from both harvest date.

Sugar:acid and pH of control and 250 nL/L 1-MCP treated fruits increased

quadratically during storage, while ascorbic acid and phenolic content each had a

quadratic decrease. Control fruits had linear decreases in both citric acid and

betacyanin content during the 28 days of storage. Fruits treated with 500, 750 and

1000 nL/L 1-MCP showed a quadratic decrease in ascorbic acid during storage,

while there was no effect of storage duration on betacyanin and phenolic

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contents. Ethylene production of fruits treated with 500, 750 and 1000 nL/L 1-

MCP was only detected after 14 days of storage. CO2 production had a similar

trend of quadratic decrease in all the 1-MCP treated fruits during the 28 days of

storage.

In conclusion, physico-chemical characteristics of red pitaya started to change

from 25 till 40 DAA i.e. towards the end of fruit growth period. Thus, the fruit

could be harvested between 30 and 40 DAA. Quality reduction and senescence

were delayed in fruits harvested at 30 DAA because conversion of acid to sugar

was delayed. Antioxidants such as ascorbic acid, betacyanin and phenolic

contents of fruits harvested at 30 DAA were not affected by storage duration.

Fruits for both harvest dates could delay ethylene production during 14 days of

storage with a minimum treatment of 500 nL/L 1-MCP, thus reducing respiration

rate and delaying senescence.

v

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

KESAN HARI PENUAIAN, TEMPOH PENYIMPANAN DAN RAWATAN DENGAN 1-METHYLCYCLOPROPENE TERHADAP KUALITI LEPAS

TUAI PITAYA MERAH (Hylocereus polyrhizus)

Oleh

MELLY NOVITA

April 2008

Pengerusi : Professor Madya Siti Hajar Ahmad, PhD

Fakulti : Pertanian

Kematangan buah semasa penuaian penting dalam mempengaruhi kualiti makan

dan hayat penstoran bagi buah-buahan. Pitaya merupakan buah bukan

klimakterik, oleh itu, ia perlu dituai pada peringkat kematangan dengan nilai

pemakanan optimum. Penstoran buah pitaya lebih daripada 7 hari pada suhu

ambient menyebabkan kulit dan isi buah berkedut, nyahhijau dan lembut

seterusnya mengurangkan kualiti. Maklumat mengenai masa penuaian yang

optimum dan kaedah penyimpanan buah pitaya masih berkurangan. Dalam kajian

ini, eksperimen pertama yang dijalankan adalah untuk menentukan hari penuaian

berasaskan pertumbuhan dan perubahan fizikal kimia buah pitaya merah sehingga

40 hari selepas antesis (HLA). Pada 25-40 hari selepas antesis, diameter, panjang

dan berat buah masih kekal malar tetapi perubahan fisikal kimia mula berlaku.

Kulit dan isi buah mula bertukar ke warna ungu. Keteguhan isi, keasidan dan

kandungan asid askorbik menurun tetapi jumlah pepejal terlarut dan pH

meningkat.

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Eksperimen kedua dijalankan untuk menentukan kesan hari penuaian dan rawatan

1-MCP selepas 28 hari penstoran terhadap perubahan fisiko-kimia buah pitaya

merah. Buah pitaya dituai pada 30 dan 35 hari selepas antesis dan dirawat dengan

0, 250, 500, 750 dan 1000nL/L 1-MCP selama 4 jam pada suhu ambient dan

kemudian disimpan selama 28 hari pada suhu 10°C. Selepas 28 hari penstoran,

kehilangan air bertambah secara linear sedangkan keteguhan isi berkurangan

secara linear pada buah yang dituai 30 dan 35 hari selepas antesis. Nilai warna L*

dan C* bertukar menyebabkan kulit buah yang dituai pada kedua-dua hari

penuaian bertukar ke warna ungu. Buah yang dituai pada 30 HLA mempunyai

peningkatan nisbah gula:asid dan pH yang rendah semasa penstoran berbanding

35 HLA. Kandungan asid askorbik dan betasianin dalam buah yang dituai pada

35 HLA menunjukkan pengurangan secara kuadratic sedangkan kandungan

fenolic mempunyai peningkatan linear semasa penstoran. Peningkatan asid

askorbik dan kandungan fenolic adalah secara linear pada buah dituai pada 35

HLA apabila dirawat dengan kepekatan 1-MCP yang semakin meningkat

sementara kandungan betasianin meningkat secara kuadratic selama 28 hari

penyimpanan. Buah yang dituai pada 30 HLA mempunyai 33% lebih CO2 pada

hari 0 penyimpanan berbanding dengan buah yang dituai pada 35 HLA. Walau

bagaimanapun, trend kuadratik bagi pengurangan penghasilan CO2 semasa

penstoran adalah sama. Tiada interaksi bagi tempoh penyimpanan dan 1-MCP

terhadap penghasilan etilena dan CO2 bagi buah yang dituai pada 30 dan 35

HLA.

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Gula:asid, kawalan pH dan rawatan 250 nL/L 1-MCP meningkat secara kuadratic

semasa penstoran sementara asid askorbik dan kandungan fenolic menurun secara

kuadratik. Bagi kandungan kedua-dua asid sitrik dan betasianin dalam buah

kawalan menurun secara linear selepas 28 hari penstoran. Buah yang dirawat

dengan 500, 750 dan 1000 nL/L 1-MCP menunjukkan penambahan kuadratik

bagi asid askorbik semasa penstoran. Tiada kesan jangka penstoran terhadap

kandungan betasianin dan fenolic. Penghasilan etilena pada buah yang dirawat

dengan 500, 750 dan 1000 nL/L 1-MCP cuma dikesan selepas 14 hari penstoran.

Penghasilan CO2 adalah menurun secara kuadratic dalam semua buah yang

dirawat dengan 1-MCP selepas 28 hari penstoran.

Kesimpulannya, buah pitaya memulakan perubahan ciri-ciri fisiko-kimia antara

25-40 HLA iaitu di akhir pertumbuhan buah. Oleh itu, buah boleh dituai pada 30-

40 HLA. Pengurangan kualiti dan kesenesenan dilambatkan pada buah yang

dituai pada 30 HLA akibat pertukaran daripada asid ke gula yang dilewatkan.

Antioksidan seperti asid askorbik, betasianin dan kandungan fenolic bagi buah

yang dituai pada 30 HLA tidak dipengaruhi oleh tempoh penyimpanan. Buah

yang dituai pada HLA di atas dapat melambatkan penghasilan etilena dengan

penstoran selama 14 hari bila dirawat dengan paras minima iaitu 500 nL/L 1-

MCP. Ini dapat menurunkan kadar respirasi dan melambatkan kesenesenan.

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ACKNOWLEDGEMENTS

Alhamdulillahi Rabbil ‘alamin, first of all I would like to express my gratitude to

the almighty Allah SWT. the most Gracious and the most Merciful; without

Whose will no any one can achieve anything. For upon His permission, I am able

to complete this thesis. My salawat and salam to His messenger, prophet

Muhammad SAW.

I am grateful to Associate Professor Dr. Siti Hajar Ahmad, the chairman of my

supervisory committee, Associate Professor Dr. Ridzwan Abdul Halim and Dr.

Phebe Ding, members of my supervisory committee for their supervision, kind

support, suggestion, discussion, ideas, encouragement and constructive comment

throughout the research and preparation of this thesis.

I would like to acknowledge and thank to Government of Nanggroe Aceh

Darussalam-Indonesia for awarding me a scholarship during my study at UPM.

My sincere gratitude is also extended to the financial support provided by

Universiti Putra Malaysia fund for this research. I am also indebted to the

financial support provided by Universitas Syiah Kuala during my study.

It is my upmost pleasure in thanking Associate Professor Dr. Anuar Abd. Rahim

and Dr. Ahmad Selamat for helping me in the statistical analysis. My sincere

gratitude is extended to all staff of agriculture faculty for their generous

cooperation and providing facilities. My colleagues in Postharvest Laboratory

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(Ms. Choon, Hidayah, Mr Raqeeb and Mr Atiq) thank you for your invaluable

guidance, technical supports, advices, comments, and suggestions. I am also

indebted to all of my friends whose help and camaraderie are very much

appreciated.

Completion of this research work, I also wish to express my deepest appreciation

to my mother “bunda Cut Dian” for her love, and continuous encouragement, and

my beloved brothers and sister who provide constant source of inspirations for

me to complete this research. Thanks for their love, patient, sacrifices, support

and motivation.

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I certify that an Examination Committee met on 17th of march to conduct the final examination of Melly Novita on her Master of Science thesis entitled “Postharvest Quality of Red Pitaya (Hylocereus polyrhizus) as Affected by Harvest Date, Storage Duration and 1-Methylcyclopropene “in accordance with Universiti Pertanian Malaysia (High Degree) Act 1980 and Universiti Putra Malaysia (High Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Siti Aishah Hasan, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Chairman) Mahmud Tengku Muda Mohamed, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Internal examiner) Yahya Awang, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Internal examiner) Awang Soh Mamat, PhD Associate Professor Faculty of Agriculture Universiti Malysia Terengganu (External examiner) HASANAH MOHD. GHAZALI, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date: 26 May 2008

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows: Siti Hajar Ahmad, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Chairman) Ridzwan Abdul Halim, PhD Associate Professor Faculty of Agriculture Universiti Putra Malaysia (Member) Phebe Ding, PhD Faculty of Agriculture Universiti Putra Malaysia (Member) AINI IDERIS, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date: 12 June 2008

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DECLARATION I declare that the thesis is my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously and is not concurrently, submitted for any other degree at Universiti Putra Malaysia at any other institutions. MELLY NOVITA Date: 23 April 2008

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TABLE OF CONTENTS Page DEDICATION ii ABSTRACT iii ABSTRAK vi ACKNOWLEDGEMENTS ix APPROVAL xi DECLARATION xiii LIST OF TABLES xvii LIST OF FIGURES xviii LIST OF ABBREVIATIONS xxi CHAPTER

1. GENERAL INTRODUCTION 1 2. LITERATURE REVIEW 5

2.1. Pitaya (Dragon fruit) 5 2.2. Physical, chemical, and physiological characteristic

changes during fruit development and storage 8 2.2.1.Fruit size 9 2.2.2.Colour 10 2.2.3.Pulp firmness 16 2.2.4.Water loss 18 2.2.5.Soluble solids concentration 20 2.2.6.Titratable acidity 23 2.2.7.pH 25 2.2.8.Ethylene 25 2.2.9.Carbon dioxide 29

2.3. 1-Methylcyclopropene (1-MCP) 31 2.3.1. Mode of action 31 2.3.2. Conditions for use 33 2.3.3. Physiological and biochemical responses of fruits

to 1-MCP 34 2.4. Antioxidants 36

2.4.1. Betacyanins 38 2.4.2. Phenolic compound 39 2.4.3. Ascorbic acid 40

3. DETERMINATION OF HARVEST DATE OF RED PITAYA (Hylocereus polyrhizus) 42

3.1. Introduction 42 3.2. Materials and Methods 44

3.2.1. Plant materials 44 3.2.2. Determination of fruit diameter 45

xiv

3.2.3. Determination of fruit length 45 3.2.4. Determination of fruit weight 45 3.2.5. Determination of peel and pulp colour (L*, C*, ho) 46 3.2.6. Determination of pulp firmness 47 3.2.7. Determination of titratable acidity 47 3.2.8. Determination of soluble solids concentration 48 3.2.9. Determination of pH 48 3.2.10. Determination of ascorbic acid 49 3.2.11. Determination of ascorbic acid by direct

colorimetric 50 3.2.12. Experimental design and statistical analysis 52

3.3. Results and Discussion 53 3.3.1. Fruit growth 53 3.3.2. Peel and pulp colour (L*, C*, ho) 58 3.3.3. Pulp firmness 68 3.3.4. Soluble solids concentration 70 3.3.5. Titratable acidity 71 3.3.6. pH and ascorbic acid contents 73

3.4. Conclusion 76

4. EFFECT OF 1-MCP ON PHYSICO-CHEMICAL CHARACTERISTICS OF RED PITAYA HARVESTED AT 30 AND 35 DAA, DURING STORAGE AT 10 oC 77 4.1. Introduction 77 4.2. Materials and Methods 79

4.2.1. Methods of treatment 79 4.2.1.1. Plant materials 79 4.2.1.2. 1-MCP treatments and storage condition 80

4.2.2. Determination of ethylene and carbon dioxide production rate 80

4.2.3. Determination of percent water loss 81 4.2.4. Determination of pulp firmness 82 4.2.5. Determination of peel and scale colour

(L*, C*, ho) 82 4.2.6. Determination of titratable acidity 82 4.2.7. Determination of soluble solids concentration 82 4.2.8. Determination of pH 83 4.2.9. Determination of ascorbic acid content 83 4.2.10. Determination of betacyanins content 83 4.2.11. Determination of total phenolic contents 84 4.2.12. Experimental design and statistical analysis 85

4.3. Results and Discussion 86 4.3.1. Ethylene and carbon dioxide production 86 4.3.2. Water loss 94 4.3.3. Pulp firmness 99 4.3.4. Peel and scale colour (L*, C*, ho) 102

xv

4.3.5. Sugar:acid 110 4.3.6. pH 121 4.3.7. Antioxidants 124

4.4. Conclusion 139 5. SUMMARY, GENERAL CONCLUSION AND

RECOMMENDATION FOR FUTURE RESEARCH 140 BIBLIOGRAPHY 143 BIODATA OF STUDENT 163 LIST OF PUBLICATIONS 164

xvi

LIST OF TABLES Table Page

1 Correlation coefficients between fruit diameter, length and weight of red pitaya from 30-40 days after anthesis (DAA). 56

2 Correlation coefficients between peel L*, C* and ho during

development of red pitaya fruit. 63

3 Main and interaction effects of harvest stage, concentration of 1-MCP and storage duration on C2H4 and CO2 productions rate of red pitaya for 0-28 days storage at 10 oC. 87

4 Main and interaction effects of harvest stage, 1-MCP

concentration and storage duration on water loss and firmness of red pitaya for 0-28 days storage at 10 oC. 96

5 Main and interaction effects of harvest stage, 1-MCP

concentration and storage duration on peel and scale (L*, C*, ho) of red pitaya for 0-28 days storage at 10 oC. 103

6 Main and interaction effects of harvest stage, 1-MCP

concentration and storage duration on pH, SSC, CA and Sugar:acid of red pitaya for 0-28 days storage at 10 oC. 111

7 Main and interaction effects of harvest stage, 1-MCP

concentration and storage duration on ascorbic acid (AA), betacyanin, phenolic content and EC50 of red pitaya for 0-28 days storage at 10 oC. 125

xvii

LIST OF FIGURES Figure Page

1 Relationship between fruit diameter (■) and fruit length (▲) with days after anthesis of red pitaya fruit. 53

2 Relationship between fruit weight and days after anthesis of red

pitaya fruit. 55

3 Relationship between peel lightness (L*) and days after anthesis of red pitaya fruit. 59

4 Relationship between peel chromaticity (C*) and days after

anthesis of red pitaya fruit. 60

5 Peel hue (ho) values during development of red pitaya fruit. 61

6 Relationship between pulp lightness (L*) and days after anthesis of red pitaya fruit. 65

7 Pulp chromaticity (C*) values during development of red pitaya

fruit. 66

8 Pulp hue (ho) values during development of red pitaya fruit. 67

9 Relationship between pulp firmness and days after anthesis of red pitaya fruit. 69

10 Relationship between soluble solids concentration and days after

anthesis of red pitaya fruit. 70 11 Relationship between citric acid content and days after anthesis

of red pitaya fruit. 72

12 Relationship between sugar:acid and days after anthesis of red pitaya fruit. 73

13 Relationship between pH values and days after anthesis of red

pitaya fruit. 74

14 Relationship between ascorbic acid content and days after anthesis of red pitaya fruit. 75

15 Ethylene production of red pitaya treated with 1-MCP at 0 nL/L

(♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 88

xviii

16 CO2 production of red pitaya harvested at 30 (▲) and 35 (■)

days after anthesis (DAA) during storage for 28 days at 10 oC. 91

17 CO2 production of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 92

18 Water loss (WL) of red pitaya harvested at 30 (▲) and 35 (■)

days after anthesis (DAA) during 28 days of storage at 10 oC. 98

19 Pulp firmness of red pitaya harvested at 30 (▲) and 35 (■) days after anthesis (DAA) during 28 days of storage at 10 oC. 101

20 Peel L* of red pitaya harvested at 30 (▲) and 35 (■) days after

anthesis (DAA) during 28 days of storage at 10 oC. 104

21 Peel C* of red pitaya harvested at 30 (▲) and 35 (■) days after anthesis (DAA) during 28 days of storage at 10 oC. 105

22 Scale L* of red pitaya harvested at 30 (▲) and 35 (■) days after

anthesis (DAA) during 28 days of storage at 10 oC. 107

23 Citric acid content (CA) of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 115

24 Sugar:acid of red pitaya harvested at 30 (▲) and 35 (■) days

after anthesis (DAA) during 28 days of storage at 10 oC. 117

25 Sugar:acid of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 118

26 pH of red pitaya harvested at 30 (▲) and 35 (■) days after

anthesis (DAA) during 28 days of storage at 10 oC. 121

27 pH of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 122

28 Ascorbic acid content of red pitaya harvested at 30 (▲) and 35

(■) days after anthesis (DAA) at different 1-MCP concentration after 28 days of storage at 10 oC. 126

29 Ascorbic acid content of red pitaya harvested at 30 (▲) and 35

(■) days after anthesis (DAA) during 28 days of storage at 10 oC. 127

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30 Ascorbic acid content (AA) of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 128

31 Betacyanin content of red pitaya harvested at 30 (▲) and 35 (■)

days after anthesis (DAA) at different 1-MCP concentration after 28 days of storage at 10 oC. 130

32 Betacyanin content of red pitaya harvested at 30 (▲) and 35 (■)

days after anthesis (DAA) during 28 days of storage at 10 oC. 131

33 Betacyanin content of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 132

34 Total phenolic content of red pitaya harvested at 30 (▲) and 35

(■) days after anthesis (DAA) at different 1-MCP concentration after 28 days of storage at 10 oC. 135

35 Total phenolic content of red pitaya harvested at 30 (▲) and 35

(■) days after anthesis (DAA) during 28 days of storage at 10 oC. 136

36 Total phenolic content of red pitaya treated with 1-MCP at 0 nL/L (♦), 250 nL/L (■), 500 nL/L (▲), 750 nL/L (●), and 1000 nL/L (*) during 28 days of storage at 10 oC. 137

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LIST OF ABBREVIATIONS

AA : Ascorbic acid

ACC : 1-aminocyclopropene-1-carboxylic acid

ACO : 1-aminocyclopropene carboxylic acid oxidase

ACS : 1-aminocyclopropene carboxylic acid synthase

AOA : Aminooxy acetic acid

AVG : Aminoethoxyvinylglycine

C* : Chromaticity

CA : Citric acid

C2H4 : Ethylene

CO2 : Carbon dioxide

CRD : Completely randomized design

DAA : Days after anthesis

DACP : Diazocyclopentadiene

DMRT : Duncan’s multiple range test

DPPH : 2,2-diphenyl picryl hydrazil

EFE : Ethylene forming enzyme

FID : Flame ionization detector

GC : Gas chromatography

h : Hour

ho : Hue

HPO3 : Metaphosphoric acid

L* : Lightness

xxi

xxii

LSD : Least significant difference

1-MCP : 1-Methylcyclopropene

NaOH : Sodium hydroxide

ns : Non significant

PROC CORR : Procedure of correlation

PROC REG : Procedure of regression

r2 : Correlation coefficient

R2 : Regression coefficient

SAM : S-adenosyl methionine

SAS : Statistical analysis system

SSC : Soluble solids concentration

STS : Silver thiosulphate

TA : Titratable acidity

TCD : Thermal conductivity detector

CHAPTER 1

GENERAL INTRODUCTION

The red pitaya (Hylocereus polyrhizus), as it is commonly known in Latin

America, is called dragon-fruit by the Asians (Mizrahi et al., 2002). This vine

cactus species is native to tropical habitats in North and South America (Briton

and Rose, 1963). The fruit size is a medium to large berry bearing large green or

red scales. The pulp is not only delicate and juicy, but it is also high in natural

antioxidants. It is also considered as a good source of vitamin C (Mizrahi et al.,

2002).

Pitaya fruit has a good potential to be developed as an export crop. Since 2000,

pitaya has been cultivated on a large scale in Malaysia as well as in other

countries. Malaysia, with a tropical climate, has a big potential to develop pitaya

as crop plant. The land planted with pitaya increased from 280 ha in 2004 to

more than 2000 ha in 2006 (Pers.comm.). Since pitaya is an extremely perishable

commodity, storage technology of pitaya will be needed to keep fruits in good

condition before sale or consumption.

Pitaya is a non-climacteric fruit (Le et al., 2000), thus, it is not capable of

continuing its ripening process if removed from the tree before it ripens. It has to

be harvested at the right stage of maturity. If the fruit is harvested at an early

stage of maturity it has poor eating quality, while if harvested at a late stage it has

a short storage life (Harman, 1981; Kader, 1994). Fruit maturity is an important