role of oxalic acid in regulation of ripening & quality pdf

Indian Agricultural Research Institute

Nirmal Kumar Meena

Roll No. 10704

IARI, New Delhi

Formula: H2C2O4

Oxalic acid (OA) is an organic acid widely

distributed in plants, fungus and animals.

Introduction

Oxaloacetate, a component of the Krebs citric acid cycle, is

hydrolyzed to oxalate and acetic acid by the

enzyme oxaloacetase.

It also arises from the dehydrogenation of glycolic acid,

which is produced by the metabolism of ethylene glycol.

Biosynthesis pathway


Functions of oxalic acid

Induce resistance in plants by

increasing activities of defense

related enzymes

Toal and Jones, 1999;

Zhang et al., 1998; Zheng

et al., 1999; Tian et al.,

2006

Reduce browning in fruits Zheng and Tian, 2006;

Yoruk et al., 2002

Act as natural antioxidant Kayashima and

Katayama, 2002

Check ethylene biosynthesis in

climacteric fruits and delay ripening

process

Wang et al., 2009; Huang

et al., 2013;Tian et al.,

2006;

Delay senescence and plant cell

death(PCD)

Sayyari et al., 2010;

Valero et al., 2011;

Huang et al., 2013)

Natural sources

Cole crops Spinach Parsley

LettuceChive

Cassava

Carambola

Papaya

Kiwi

Bilimbi

C2H4

System 1 System 2Phase

transition

ACS2,4ETRRIN CTR

ACC

Synthase

ACS1,2

ACS6

Schematic diagram of mechanism of oxalic acid

Case Studies

Indian Agricultural Research Institute, New Delhi

Effect of oxalic acid application on ‘Samar Bahisht

Chaunsa’ mango during ripening and postharvest

Razzaq et al., 2015

LWT - Food Science and Technology 63 :152-160

Objective:

To investigate the effect of postharvest application of OA

on the activities of fruit softening and anti-oxidative enzymes

as well as biochemical attributes of ‘Samar Bahisht Chaunsa’

mango fruit quality during ripening and cold storage.

Case study- I


Materials and methods

Selection of fruits: Samar Bahist mango fruits were harvested

Treatments:

Fruits immersed in an aqueous solution of different OA

concentrations (0, 1, 3 and 5 mmol/L) for 10 min.

Treated fruits were allowed to ripening at 32 ± 2º C for 7 days,

or stored at 12 ± 1º C up to 28 days.

Biochemical analysis

Quality attributes estimated at interval of 2 days and 7days

during ripening and storage respectively.

Results and discussion

Fig. 1. Effect of OA on ethylene production (A and B) and respiration

rate (C and D)

Effect of OA treatment on activities of fruit softening enzymes exo-PG and pectin

esterase during ripening and storage

Fig.3. Effect of OA on on activities of antioxidative enzymes Peroxidase (POX) (C and D)

and catalase (CAT) (E and F) of ‘Samar Bahisht Chaunsa’ mango fruit during ripening

(RP) at ambient conditions and cold storage (SP).

Inferences

Exogenous application of oxalic acid @ 5mmol/L

reduced ethylene production, respiration and activities of

exo-PG activities.

OA treatment exhibited higher activities of catalase

(CAT) and peroxidase (POX).


Effect of oxalic acid on ripening attributes of banana

fruit during storage

(Huang et al., 2013)

Postharvest Biology and Technology 84:22–27

The objective of the present study was to investigate the role

of oxalic acid in postharvest ripening of banana fruit

Case study- II


Methodology:

Selection of banana cv. Brazil

↓

Oxalic acid treatment

[ control, 5, 10 and 20 mM] at at

room temperature (23±2 ◦C)

↓

Selection of best treatment for

further biochemical study

↓

20 mM oxalic acid for 10 min

and control were selected

↓

Stored at 23±2ºC

↓

Biochemical analysis at 4days

interval

Results and discussion

control

20 mM

Change in the ethylene production and respiration of banana fruit treated with oxalic acid

during storage at 25ºC.

Change in SOD activity in peel tissues

of banana fruit treated with oxalic acid

Change in MDA activity in peel tissues

of banana fruit

control

20 mM

control

20 mM

Changes in flesh firmness and chlorophyll fluorescence (Fv/Fm) (C) of banana

Inference:

• Oxalic acid treatment reduced rate of ethylene and

respiration, higher SOD and least MDA content.

• OA delayed the decrease firmness and chlorophyll

degradation.


Physiological and biochemical response of harvested

plum fruit to oxalic acid during ripening or shelf-life

Wu et al., 2011

Food Res.Int.44 (2011) 1299–1305

Objective:

To investigate the effect of postharvest dips of ‘Damili’

plums with oxalic acid on ripening or senescence during

storage or shelf-life.

Case study- III


Oxalic acid treatments:

Fruits immersed in OA concentration range

0.5-10mmol/L for 3 minutes. Treatment with

5mmol/L was most effective.

OA concentration 5mmol/L was taken for

further investigation.

Storage conditions:

• Fruits stored at 25o 12 days.

Fruit material: Plum fruits cv. ‘Damili’ were

selected

Materials and Methods

0 3 6 9 12 15

Effect of oxalic acid treatment (5mmol/L) on ethylene production rate of plum fruits


Effect of oxalic acid treatment (5mmol/L) on anthocyanin content and firmness of

plum fruits


Effect of oxalic acid treatment (5mmol/L) on PG, PME, PAL enzymes and chlorophyll of plum

fruits

Postharvest application of oxalic acid significantly delayed the

endogenous ethylene production and softening of plum.

Oxalic acid treatment reduced anthocyanin synthesis, PG, PME and

PAL enzymatic activities that lead to higher shelf life.

Chlorophyll florescence decreased very slowly in treated fruits as

compare to control.

Inferences


Expression of expansin gene, MiExpa1 and activity of

galactosidase and polygalacturonase in mango fruit as

affected by oxalic acid during storage at room temperature

Objective:

To investigated the effects of oxalic acid treatment on the gene expression

and enzymatic activities of PG and galactosidase in mango fruit during storage

at room temperature.

( Zheng et al., 2012)

Food Chemistry 132: 849–854

Case study- IV


Methodology

Treatments:T1: Dipping in water (Control)

T2:Dipping in 5 mM Oxalic acid @25°C for 10 min

Storage conditions: 25 ± 1 °C with 95% RH.

Selection of mango fruits cv. Zilli

Gene sequencing and biochemical analysis


Results

Expression of MiExpA1 gene

in untreated (control) and

oxalic acid treated mango cv.

Zill fruit


Changes in activity of b-Gal

flesh of untreated (control)

and oxalic acid treated

mango cv. Zill fruit

Changes in the fruit

firmness of untreated

(control) and oxalic acid

treated mango cv. Zillfruit


Changes in activity of PG in the flesh of untreated (control)

and oxalic acid treated mango cv. Zill fruit


Inference

Application of oxalic acid significantly inhibited decrease in flesh

firmness, notably suppressed and delayed MiExpA1 expression

in the peel and the flesh, and also significantly decreased

activities of enzymes in the flesh.


Case study- V

Response of jujube fruits to exogenous oxalic acid

treatment based on proteomic analysis

Wang et al.,2009

Plant Cell Physiol. 50(2): 230–242

To investigated the physiological response of jujube fruit to OA treatment

Objective

Methodology

Treatments:T1: Dipping in water (Control)

T2:Dipping in 5 mM Oxalic acid @20°C for 10 min

Storage conditions: 20 °C with 95% RH.

Selection of jujube fruits

Biochemical analysis


Effect of oxalic acid treatments (5mmol) on reddening index and

chlorophyll degradation of jujube fruits during storage

Results

Control fruits OA treated fruits


Effect of oxalic acid treatments (5mmol) on ethylene evolution

and respiration rate of jujube fruits during storage

Effect of oxalic acid treatments

(5mmol) on ACS, ACO and

ADH activity of jujube fruits

during storage

Inference

From the study it was found that OA concentration of 5mM

could delay senescence by reducing ethylene production,

repressing fruit reddening and suppressing ADH 1 protein.


Conclusion

In conclusion, oxalic acid treatment

5mmol to 20mmol significantly delayed

ethylene production, respiration rate and

activities of senescecent related enzymes.

The results obtained from these studies

provide evidence of the ability of OA to

maintain appearance, higher shelf life and

quality.


Future thrust:

Further work is needed to understand

better mechanism by which oxalic acid

delay ripening at molecular level
