Evaporative cooling system for storage of fruits and vegetables - a review

Abstract

Horticultural produce are stored at lower temperature because of their highly perishable nature. There are many methods to cool the environment. Hence, preserving these types of foods in their fresh form demands that the chemical, bio-chemical and physiological changes are restricted to a minimum by close control of space temperature and humidity. The high cost involved in developing cold storage or controlled atmosphere storage is a pressing problem in several developing countries. Evaporative cooling is a well-known system to be an efficient and economical means for reducing the temperature and increasing the relative humidity in an enclosure and this effect has been extensively tried for increasing the shelf life of horticultural produce in some tropical and subtropical countries. In this review paper, basic concept and principle, methods of evaporative cooling and their application for the preservation of fruits and vegetables and economy are also reported. Thus, the evaporative cooler has prospect for use for short term preservation of vegetables and fruits soon after harvest. Zero energy cooling system could be used effectively for short-duration storage of fruits and vegetables even in hilly region. It not only reduces the storage temperature but also increases the relative humidity of the storage which is essential for maintaining the freshness of the commodities.

Preservation of Postharvest Quality of Leafy Amaranth (Amaranthus spp.) Vegetables Using Evaporative Cooling

“…The medium could be charcoal, sand, clay, or any other material that is porous enough to hold water. This medium is kept wet and as dry/hot air flows over it, the water therein evaporates resulting in a cooling and humidifying effect [6]. The measure of effectiveness is based on how close the air temperature leaving the evaporative cooler approaches the outdoor wet bulb temperatures [6].…”

Insulin storage in hot climates without refrigeration: temperature reduction efficacy of clay pots and other techniques

“…The potential utility of a clay pot or other device in a particular location can be predicted by calculating the wet bulb temperature using an online psychrometric calculator , and then using the equation with relative cooling effect expressed as a percentage, 62.8% being a reasonable assumption if one of the eight most efficacious devices is used.…”

“…In many other cases in Africa, Asia and the Caribbean, insulin is stored in water-filled clay pots or other traditional storage devices, of various designs, using evaporative cooling [10][11][12][13][14][15][16][17][18][19][20]. Such clay pots ('zeer' pots, 'matka') are traditionally used in hot climates to keep water and foodstuffs cool [24,25].…”

Substantiaton of selecting the method of pre-cooling of fruits

“…Such loading of chambers requires less cooling productivity of the equipment, and this, in its turn, has a positive effect on economic indicators of storage [12].…”