1. Biochemistry of fruit ripening
Prof. Harshraj. S. Shinde
K. K. Wagh College of Agril. Biotech, Nashik. India
2. Outlines
• Increase in rate of respiration
• Hormonal change- Ethylene
• Change in chlorophyllchlorophyll content
• Synthesis of carotenoids, anthocyanin and XanthophyllXanthophyll
• Increase in activity of enzymes
• Synthesis of volatile compounds
• Synthesis of simple sugar
4. Increase in rate of respiration
• Respiration is a fundamental process.
• The major storage products sucrose and
starch are fully oxidized to CO2and H2O
• with the release of energy (ATP).
• There are two pathways in conversion of
starch or sucrose to glucose-6 P
glycolysis
pentose phosphate pathway
6. Hormonal change- Ethylene
• Ethylene is a ripening hormone.
• Even at minute quantities it stimulates
respiratory activity, induces ripening, and
hastens onset of climacteric rise.
8. Hormonal change- Ethylene
• Promotes its own biosynthesis in ripening climacteric
fruits.
• Application of ethylene to climacteric fruits hastens the
onset of climacteric rise
• Accompanied by an increase in oxygen uptake
• This process is not reversed.
• In non climacteric fruits an increase in oxygen uptake
accompanied by application of ethylene and respiratory
activity returns to the level of the control once ethylene
treatment is terminated.
9. Change in chlorophyllchlorophyll content
• During ripening ethylene promotes the
degradation of chlorophyll during maturation.
• Light or dark conditions may have different
effects.
• Biosynthesis of anthocyanins in red cabbage is
stimulated by ethylene when exposed to light.
10. Change in chlorophyll content
1.. Replacement of Mg atom in the chlorophyll by
hydrogen atom under acidic conditions with the
formation of pheophytin.
Pheophytin formation: a color change from bright
green to dull olive green.
Examples: Stored frozen peas, frozen spinach.
2. Hydrolysis of chlorophyll to chlorophyllide and phytol
–
catalyzed by chlorophyllase –
followed by a replacement of Mg atom with hydrogen
resulting in the formation of pheophorbide
(Brining of cucumbers-major degradation product)
11. 3. Bleaching of chlorophyll by the action of
lipoxygenase, peroxidase and catalase.
• Degradation of fatty acid hydro peroxides
• Oxidation-reduction reaction in the presence of
oxygen
12. Synthesis of carotenoids
• The color change from green to orange or red in
many fruits is due to the loss in chlorophyll
• Carotenoids isoprenoid compounds
• composed of isoprene units joined head to tail to
form a system of conjugated double bonds.
Carotenes (hydrocarbons)
Xanthophylls (their oxidized derivatives :
hydroxy, oxy,and epoxy compounds)
13. Color Changes-AnthocyaninsAnthocyanins
• Anthocyanins are responsible for pink, red, purple, and
blue colors.
• Water-soluble pigments formed during maturation of
fruits (strawberries, apples, cranberries, grapes.)
• and vegetables (red cabbage, radish, red onion...)
• Anthocyanins are flavonoid pigments whose structure is
based on the phenyl propanoid nucleus
14. Synthesis of XanthophyllXanthophyll
• Occurs in banana.
• After treating unripened (green) bananas with
ethylene they gets converted into ripened (yellow).
• Process is due to synthesis of Xanthophyll
15. Increase in activity of enzymes
• Softening of fruits during ripening
• Softening is due to degradation of pectin by
pectinase
• Types of pectinase
• PMG, polymethyl galacturonases;
• PG, polygalacturonases
• PE, pectin esterase
• PL, pectin lyase
16. Increase in activity of enzymes
• Degradation of cellulose during ripening
(strawberries, avocados) by cellulase.
• Hydrolysis of galactans to galactose by
β-galactosidase (apples, strawberries,
tomatoes) during ripening.
17. Synthesis of volatile compounds
• Aroma is produced by volatiles synthesized during
ripening
• includes aldehydes, esters, lactones, terpenes, and sulfur
compounds.
• Volatiles originate from proteins, carbohydrates, lipids, and
vitamins.
• Taste is provided by many nonvolatile components,
including sugars and acids present in fruits.
18. Flavor-Aroma formation
• Short-chain unsaturated aldehydes and
alcohols (C3-C6) and esters are important
contributors to the aroma.
a) Amino acids
b) Fatty acids
19. Synthesis of simple sugar and organic
acid
• Typical taste of fruits is determined by the content
of sugars and organic acids.
• Also phenolic compounds and tannins may affect
the taste.
• During ripening starch is converted into sucrose,
glucose and fructose.
• Starch hydrolysis is a major change during ripening
of climacteric fruits.
20. • The concentration of organic acids also reach
to a maximum during growth and development
of fruit on tree.
• There is a decrease during storage highly
depending on temperature.
• Citric and malic acids-intermediates of Krebs
cycle.
• Other acids: ascorbic acid (reduced form),
oxalic acid.
