Biochemical changes during post harvest storage of pummelo

1. Biochemical changes during
post harvest storage of pummelo
Submitted to:
Dr Monica Sachdeva Taggar
Assistant Biochemist
Submitted by:
Mandeep Kaur

2. Introduction to Pummelo
Pummelo (Citrus grandis) is one of the largest citrus fruits.
The fruit flesh is normally consumed rather than processing it into a juice.
It is renowned for its good flavor and juicy texture.
In addition, it’s flesh contains important nutrients including vitamin C,
potassium, pectin, natural folic acid and chromium.
Local NRCC Pummelo - 2 PTF - 4

3. Physio-biochemical changes in
harvested pummelo fruit
Respiration rate varies with the state of maturity and ripening in
many fruits.
The rate increasing to a maximum just prior to full ripening the phase
called the climacteric.
Citrus spp. (orange, acid lime, lemon, grapefruit and pummelo) are
non-climacteric fruits.
The respiration rate does not accelerate after harvesting.
Non-climacteric fruits are best when ripened before harvesting.

4. Non – Climacteric Fruit Ripening
Fig: Growth, respiration and ethylene production in non-climacteric fruits (Wills, 2007)

5. Ke D, 1993; Yang and Hoffman1984
Ethylene Biosynthesis & Ripening

6. Changes in Chlorophyll content

7. Synthesis of carotenoids & anthocyanin
The colour change from green to orange or red in many fruits is due
to the loss in chlorophyll and synthesis of carotenoids.
Carotenes (hydrocarbons) Xanthophylls (their oxidized derivatives :
hydroxy, oxy and epoxy compounds).

8. Increase in activity of enzymes
Softening of fruits during ripening is due to degradation of pectin by
pectinase like pectinase, polymethyl galacturonases, polygalacturonases,
pectin esterase, pectin lyase.

9. Starch hydrolysis
As the fruit maturity progresses, the starch reserves get hydrolysed into sugars
(glucose, fructose or sucrose).
Further the complex sugars viz. sucrose are broken down into simple sugars
viz. glucose and fructose with the catalytic action of enzyme invertase.

10. Flavour/aroma compounds
The flavour consists of basically three components viz. aroma, taste and
mouth feel.
The major flavouring compounds identified are esters, alcohols, aldehydes,
acids and ketones.
Product Flavour
Grape fruit Nootakatone
Lemon Citral
Citral

11. Volatile Compounds & Aroma Profiles
Pink and white pummelo fruit contained similar volatiles, which
mainly consisted of limonene, cis-β-ocimene, α-terpinene, linalool,
methyl anthranilate, and indole.
Volatiles originate from proteins, carbohydrates, lipids, and vitamins.
Their primary difference was in the concentration ratio between
limonene and linalool.
Major volatiles in pummelo peels were terpene hydrocarbons.
Pink pummelo peel contained higher levels of aldehydes (e.g.
octanal, decanal and citral).
Whereas some trace-level important compounds (e.g. β-sinensal, α-
sinensal and nootkatone) were found only in white pomelo peel.

12. Ascorbic acid/ vitamin C
L-ascorbic acid (Vitamin C) is the naturally occurring ascorbic acid in fruits.
A gradual rise in ascorbic acid content with fruit growth has been observed
and the levels decline with the advancement of maturity and onset of fruit
ripening and postharvest handling.
It is found to be low at the time of harvest.
The upsurge in ascorbic acid content during ripening of certain fruits could
be due to increased lipid peroxidation, since fruit ripening is considered as
an oxidative phenomenon necessitating the turnover of active oxygen
species.
The decrease in vitamin C during the later stages of ripening might be due to
its oxidation to dehydroascorbic acid.
The ascorbic acid content of pummelo fruits ranged from 37.70 to 84.49
mg/100ml juice.

13. Fig. Changes in total phenols (TP) (A) and total ascorbic acid (TAA) (B) in juice
sacs of HR, BR and HuR during postharvest storage.

14. Phenols and flavonoids
During ripening, there is a gradual change in certain secondary metabolites with
the commencement of phenolic pathways.
The newly synthesized phenolic compounds play a crucial role in the fruit
pigmentation, as well as its pathogen resistance.
The phenolic content of most fruits declines from early growth stages till
attainment of physiological maturity. During maturation and development, the
phenolic compounds undergo a sequence of intricate metabolic processes,
resulting in compositional changes of the plant and plant derived foods.
Flavonoids are present in various horticultural commodities in the form of
conjugates i.e. glycosylated or esterified forms.
Characteristic flavonoid compounds present in pummelos: Anthocyanin &
Lycopene
Total flavoinoid content of the pummelo juice varied from 11.47 to 57.80 mg
QE/100ml.

15. Fig: Changes in total antioxidant capacity (TAC) (A) & DPPH radical scavenging activity
(B) in juice sacs of Hongroumiyou (HR), Bairoumiyou (BR) and Huangroumiyou (HuR)
pummelo during postharvest storage.
Total antioxidant capacity (TAC) & DPPH radical scavenging activity

16. Fig. The possible mechanism of changes in metabolisms of antioxidant and cell wall in
juice sacs of three pummelo cultivars during postharvest storage

17. THANK
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