The use of evaporative cooling in lowering the temperature of ambient air and improving the relative humidity of the draft air is very old (Watt 1997).

Maintaining the freshness of vegetables and fruits even for a short period in a tropical environment is difficult. Fresh fruits and vegetables usually deteriorate faster than other products because they increase in respiration while in stor- age, due to high moisture content and high tropical heat which lead to a number of physical and physiological changes affecting the viability, quality and marketability of the produce.

The use of evaporative cooling system showed improve- ment in the shelf life of fruits and vegetables stored. The stored vegetables in the cooler showed higher moisture and vitamin C content while the withered control has higher ash, protein, fibre and carbohydrate content. However, the fruits stored in the cooler had lower vitamin C and higher moisture than the control which showed good quality and crispiness while the control deteriorated at the same period.

The results suggest that the integration of evaporative cooling system with good sanitation along the marketing channel from the harvest point until the consumption point will help to attain high quality level of freshness for some period.
Precooling refers to the rapid removal of field heat from freshly harvested fruits and vegetables prior to shipping, storage or processing.

Reasons for Precooling

Precooling is a very important step in the post-harvest stage of the perishable-produce industry to reduce the loss in quality of produce once it’s been picked. and increase the shelf-life of fresh produce. Higher quality and longer shelf-life means more profits to produce growers.

Another benefit to precooling is the limiting of microorganism growth. Colder temperatures inhibit growth of both existing and new microbes.

Studies show the importance of precooling. For storage and long distance transportation of produce, the question isn’t if you should precool, it’s how you should precool.

Precooling can be achieved by Forced-air evaporative cooling - Evaporation not only lowers the air temperature surrounding the produce, it also increases the moisture content of the air. This helps to prevent the drying out of the produce, and therefore extends its shelf life. It is economical and can store the fruits and vegetables for 3 to 5 days without any significant loss

The Evaporative pre cooling design depends on the materials available and the users requirements.

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