Methods of cooling

The selection of pre-cooling method depends on three factors:

• The temperature of produce at harvest products are
• Physiology of produce
• Desired postharvest life.

The methods of pre-cooling are:

a) Room cooling or air-cooling: In this case, the products are allowed to cool in normal room temperature without any artificial means.

b) Forced air-cooling: In this case the cold air is forced (passed) through the packages and around each piece of the produce. Forced air-cooling can cool produce about one-quarter to one-tenth the time for room cooling.

c) Hydro-cooling: By sprinkling cold water on the surface of the commodities. The water should be clean, chlorinated or contain same fungicide or bactericides.

d) Contact icing: contracting with ice pieces cools the commodities. Sometimes ice pieces are kept on the top of the fruits during transport this is known as top icing.

e) Vacuum icing: Vegetable, which has high surface to volume ratio, is cooled in vacuum ex. Lettuce. In vacuum there is severe loss of moisture to avoid this the vegetable should be water either before or after passing into vacuum. The rate of cooling largely depends upon surface to volume ratio of the commodities. The vegetables that have high surface to volume ratio are cooled faster than the fruit.

f) Evaporative cooling: In this case dry air with low relative humidity is passed through the surface of the commodities. The commodities are cooled as they lose water to the environment.

g) Overnight cooling: It is generally practiced in temperate countries. The harvested commodity is kept overnight in open air for cooling.