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
Indian Agricultural Research Institute
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)
C2H4
System 1 System 2Phase
transition
ACS2,4ETRRIN CTR
ACC
Synthase
ACS1,2
ACS6
Schematic diagram of mechanism of oxalic acid
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
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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).
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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
Indian Agricultural Research Institute
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
Inference:
• Oxalic acid treatment reduced rate of ethylene and
respiration, higher SOD and least MDA content.
• OA delayed the decrease firmness and chlorophyll
degradation.
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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
Indian Agricultural Research Institute
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
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Effect of oxalic acid treatment (5mmol/L) on anthocyanin content and firmness of
plum fruits
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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
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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
Indian Agricultural Research Institute
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
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Results
Expression of MiExpA1 gene
in untreated (control) and
oxalic acid treated mango cv.
Zill fruit
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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
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Changes in activity of PG in the flesh of untreated (control)
and oxalic acid treated mango cv. Zill fruit
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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.
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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
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Effect of oxalic acid treatments (5mmol) on reddening index and
chlorophyll degradation of jujube fruits during storage
Results
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.
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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.
Indian Agricultural Research Institute
Future thrust:
Further work is needed to understand
better mechanism by which oxalic acid
delay ripening at molecular level
Indian Agricultural Research Institute