Method of pre-cooling : 

i. Room cooling 

ii. Forced air cooling 

iii. Hydrocooling 

iv. Vacuum cooling 

v. Package icing 

Description any two: 

(i) Room cooling: It is low cost and slow method of cooling. In this method, produce is simply kept into a cool room and cool air is allowed to circulate. 

Advantages: 

(a) Produce can be cooled and stored at the same room thus saves on handling costs. 

(b) No extra cost for pre-cooling equipment. 

(c) Suits for crops, which are marketed soon after harvest. 

Disadvantages: 

(a) It is too slow method of cooling 

(b) Space requirements for room cooling are more as compared to storage, thus loss of storage capacity. 

(c) Excessive water is lost from the produce due to slow cooling. 

Horticulture crops suitable for rooms cooling are: 

Potato, onion, apple and citrus 

(ii) Forced-air cooling: Forced air-cooling is mostly used for wide range of horticultural produce and it is fastest method of pre-cooling. Forced air-cooling pulls or pushes air through the vents/holes in storage containers. In this method uniform cooling of the produce can be achieved. 

Advantages: 

(a) Fast method of pre cooling 

(b) Suitable for wide range of highly perishable commodities.

(c) Uniform cooling, if containers are properly aligned. 

Horticultural produce suitable for forced air cooling are: 

Grapes, Berries, Pears, Peach, Oranges, Strawberries tomato, and other tropical and subtropical fruits. 

(iii) Hydrocooling : The use of cold water is an old and effective cooling method used for quickly cooling a wide range of fruits and vegetables before packaging. This method of cooling not only avoids water loss but may even add water to the commodity. 

Advantages : 

(a) Less energy is used as compared to forced air cooling. 

(b) Moisture loss does not take place. 

Disadvantages : 

(a) Most of the packages don’t tolerate wetting. 

(b) Wax layer of some fruits like pear, plum, apple are removed by using spray type of hydrocooler Horticultural produce suitable for hydrocooling are: Mango, peach, asparagus etc. 

(iv) Vacuum cooling: Vacuum cooling take place by water evaporation from the product at very low air pressure. In this method, air is pumped out from a larger steel chamber in which the produce is loaded for pre-cooling. Removal of air results in the reduction of pressure of the atmosphere around the produce, which further lowers, the boiling temperature of its water. As the pressure falls, the water boils quickly removing the heat from the produce. 

Advantages : 

(a) Packed produce can be cooled if the pack allows moisture transfer. 

(b) Fast and uniform cooling takes place. 

(c) Most energy efficient method. 

Disadvantages : 

(a) High initial capital cost 

(b) Produce losses more moisture To overcome the more loss of water from the produce, 

(v) Package-icing: In some commodities, crushed or flaked ice is packed along with produce for fast cooling. However, as the ice comes in contact with the produce, it melts, and the cooling rate slows considerably. The ice keeps a high relative humidity around the product. Package ice may be finely crushed ice, flake ice or slurry of ice. Liquid icing distributes the ice throughout the container, achieving better contact with the product. 

Precaution: Packaged icing can be used only with water tolerant, non-chilling sensitive products and with water tolerant packages (waxed fiberboard, plastic or wood).