PHYSIOLOGICAL CHANGES IN VEGETABLES AFTER HARVESTING.pptx

Post harvest physiological changes in vegetables
Respiration, Transpiration, Ethylene Production, Growth and Development, Physical Damage.
Horticulture.

1. PHYSIOLOGICAL CHANGES IN VEGETABLES AFTER HARVESTING

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 O 2 is used and CO 2 is produced C 6 H 12 O 6 + 6 O 2 6C O 2 + 6H 2 O + 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 CO 2 , reduced O 2 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