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
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 varies with stage of maturity and ripening.
• Respiration rate
• Increase in RR prior to
• Peaches, peas, mangoes
• Respiration rate does
not accelerate after
• Best when ripened
• Citrus fruits and
4. COMPONENTS OF CELL WALL
Pectic substance in cell wall and middle lamella
starts degrading due to increased levels of two
enzymes: pectinesteraces and
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
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
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
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
Microbial spoilage: Vegetables are susceptible to the action of a variety of
microorganisms, thereby leading to substantial decay losses during post