COLD PRESERVATION OF PERISHABLE FOOD PRODUCTS

Abstract

Food products of perishable nature are needed to be preserved from spoiling using the precooling technique. Precooling is the process of cooling fruits and vegetables as soon as possible after the harvest and prior to transportation over long distance to a cold storage warehouse and marketing. The present work is an attempt to investigate experimentally the heat transfer behaviour during precooling of fruits and vegetables in rectangular duct under forced convection. In the experimental study done of RAC lab at (MIED, IITR), on rectangular ducts the food commodities investigated are apple, papayas and grapes. Forced air cooling is achieved by suspending the food inside a 4 m long rectangular air duct of 0.3 x 0.3 m section of Galvanized Iron sheet which is insulated with 1 cm thick puff sheet. The humidity inside the duct is to be maintained constant. The temperatures of the cold air outside package and of the food product at different locations inside the package are to be measured at regular time intervals. For better exposure of food commodity to the surrounding cold air, the fruits will be cooled in wire mesh package size 21 x 21 x 21 cm. The air is circulated through the duct by means of a blower powered by 1.5 hp electric motor. The air is then made to pass through two coils. One coil is made evaporator coil of 5 ton capacity vapor compression plant and another coil has the forced flow of chilled water, which rejects heat to the refrigerant inside the chiller. The condenser cooling water cooled by means of induced draft cooling tower.