1. PRESENTED BY:
PRACHI NARANG
A0989216074
Bsc(Hons.)- Microbiology
Semester: 6 (AIMT)

2. What is post harvest?
 The post-harvest sector includes all points in the value chain from
production in the field to the food being placed on a plate for consumption.
Postharvest activities include harvesting, handling, storage, processing,
packaging, transportation and marketing.
 In fruits and vegetables, the synthesis of organic compounds halts after
the harvest.
They undergo various physiological changes during storage:
 Bulbs, roots, tubers and seeds become dormant.
 Fleshy tissues undergo ripening after maturation
 Senescence occurs quite rapidly with an accompanying loss of palatability.

3. Certain biochemical activities also occur in fruits and vegetables:
RESPIRATION RATE
Respiration rate varies with stage of maturity and ripening.
 Classified into:
Climateric fruits
• Respiration rate
accelerates after
harvesting.
• Increase in RR prior to
senescence.
• Peaches, peas, mangoes
Non-Climateric fruits
• Respiration rate does
not accelerate after
harvesting.
• Best when ripened
before harvesting.
• Citrus fruits and
grapes

4. COMPONENTS OF CELL WALL
 Pectic substance in cell wall and middle lamella
starts degrading due to increased levels of two
enzymes: pectinesteraces and
polygalacturonases.
 Pectic acid(lost gel forming property) is found in
over ripe, very soft fruits and vegetables.
 On the other hand, some sugars are released
from the complex polysaccharides which results
in over sweetening of ripened fruits.

5. It is a genetically programmed highly coordinated physiological process.
Enzymes like lipase, invertase, chlorophyllase, pectic enzymes and
peroxidase are observed to increase. Changes occur during ripening:
 Change in Color (green to yellow or orange red). There is a Breakdown of
chlorophyll.
 Softening of the flesh; protopectin is converted into pectin.
 There is a decrease in acidity; increase in sugars, volatile substances and
essential oils. When harvested, a banana contains 20% starch and only
1% sugar but after ripening the proportions are reversed.
 Decrease in astringent property making a pleasant flavour.
The optimum temperature and humidity for ripening are 20 degree
Celsius and 90-95% relative humidity.

6.  Banana releases ethylene gas to help itself ripen.
INDUCED RIPENING OF FRUITS
 After harvesting, some fruits fail to ripen especially bananas. So they are
exposed to the ripening inducers such as smoke, ethylene gas and calcium
carbide.
 Calcium carbide pellets are used to hasten ripening of mangoes.
 Banana bunches are exposed to smoke (up to 12 hours) for ripening.

7.  Storage is a very important part after harvesting as it can increase the
product’s shelf life and slow down the post harvest changes in fruits and
vegetables. Only a few fruits can be stored for an extended period of time
in cold or cellular storages like apples.
 Each fruit has its own optimum temperature for storage and also proper
air circulation ensures the successful storage of fresh fruits.
 Commercial storage of fruits is satisfied with low temperatures close to 0
degree Celsius and 85% relative humidity.
 Fresh fruits absorb and emit odours.
 Strong flavour fruits can be stored in tight containers.
 Most vegetables have a very short storage life because of their rapid
respiration.

8.  Fresh green vegetables are kept fresh and crisp in covered containers or
plastic bags in the refrigerator.
 Storing in too much moisture can spoil and decay vegetables.
 Seeds such as peas can remain fresh longer if left in the pods.
 Tubers and bulbs can be stored in a cool place without refrigeration.
 To extend the storage life of perishable and semi-perishable food products,
MAP(Modified atmospheric packaging) is introduced.
 One more method for storing is to adjust the permeability of the
packaging to match the respiration of the fruits/vegetables so the the
gases inside are optimally maintained. This reduces the rate of
respiration, inhibits the synthesis and retards microbial growth.

9. Very low respiring: Potato, Onion
Low respiring: Carrot, Celery, cabbage
Moderately respiring: Cauliflower, lady’s finger
High respiring: Broccoli, pod-pea, sweet corn
There are various factors that can affect storage life like:
 Loss of water: It effects the appearance, texture, flavour and weight.
 Respiration and metabolism: Vegetables having low respiring
commodities have a long shelf life compared to high respiring
commodities.
 Microbial spoilage: Vegetables are susceptible to the action of a variety of
microorganisms, thereby leading to substantial decay losses during post
harvest handling.