2. POSTHARVEST PHYSIOLOGY
• The life of fruits and vegetables can be divided
into three major physiological stages
• The physiological changes after harvest till
senescence is called postharvest physiology.
3. MAJOR POSTHARVEST PHYSIOLOGICAL CHANGES
• Respiration
• Ethylene production
• Growth and development
• Transpiration
• Physiological breakdown
• Physical damage
4. RESPIRATION
• Stored organic materials (carbohydrates, protein,
and fat) are broken down into simple products
• Food reserves, especially sugars, get degraded in
order to produce energy (in the form of ATP and
NADH) to maintain cellular metabolic activity.
• Energy is released
• O2 is used and CO2 is produced
C6H 12 O6 + 6O2 6CO2 + 6H2O + Energy (686 kcal)
5. EFFECTS OF RESPIRATION
• Reduced food value (energy value)
• Reduced flavor due to loss of volatiles
• Reduce weight
The rate of deterioration of vegetables
is directly proportion to the respiration rate
6. ETHYLENE PRODUCTION
• Naturally produced by vegetables as they
ripen
• Can lead to premature ripening if produced in
excess
• The presence of high CO2, reduced O2 and low
temperature can inhibit ethylene production
7. GROWTH AND DEVELOPMENT
• In some vegetables growth and development
continue even after harvest
Example
• Sprouting of potato, onion and garlic
• Rooting of onions
8. TRANSPIRATION
• A physical process in which high amount of
water is lost
• Occurs through the cuticle, epidermis,
stomata and hairs
• Produce stored at high temperature will have
high transpiration rate
• It causes loss in quality i.e., undesirable
changes in colour, taste and nutritive value
9. EFFECTS OF TRANSPIRATION
• Loss in weight
• Loss in appearance (Shrinking)
• Loss in texture (softening, loss of crispiness
and juiciness)
10. PHYSIOLOGICAL BREAKDOWN
• Occurs when produce is exposed to an
undesirable temperature
• Chilling injury - when commodity is stored
below their desired storage temperature
• Heat injury - when commodity is exposed to
direct sunlight or excessively high temperature
• Freezing injury - when commodity is stored
below their freezing temperature
11. PHYSICAL DAMAGE
• Mechanical injury during harvesting, handling,
storage and transportation
• Bruising due to vibration,
impact and compression
