Performance evaluation of a scoria evaporative cooler for storage of mango fruits

Abstract

The scoria evaporative cooler designed for this project applies the principle of evaporative cooling to reduce the temperature while at the same time increasing relative humidity inside the storage chamber. The modern preservation systems such as refrigerators are out of reach to most farmers; in-terms of cost and electricity which is costly and inappropriate for remote areas without electricity. The design consists of a cabinet box type whose dimensions of length, width, and height were 1000mm, 1000mm, and 1400mm, respectively. The performance of the scoria evaporative cooler was evaluated by monitoring the vitamin C, the weight, total soluble solutes, and firmness of the mango fruits and also the temperature and relative humidity throughout the study period. Mature and green apple mangoes were sourced directly from a farm in Tala Machakos County. Three labelled mangoes were randomly selected for evaluation of physiological weight and peel colour changes during storage and subsequent evaluation was repeated on the same fruits. The measurement of firmness, vitamin C and total soluble solids which involved destruction of fruits, the fruits were randomly selected, evaluated and discarded. The shelf-life and quality attributes (viz., physiological weight, firmness, TSS, and vitamin C) of the fruit stored in the cooler were evaluated against the fruits stored under ambient conditions. The temperature and relative humidity of storage environment for the cooler was of average value of 19.27 oC and 88.88% whilst the ambient storage were on average 30.41 oC and 35.28% respectively. Thus, the cooler lowered the storage temperature by 11.14 oC as compared to ambient conditions. This technology extended the shelf life of the apple mangoes by ten days as compared to storage under ambient conditions and this also preserved the quality of the fruit thereby reducing the losses and hence will make mango farming more profitable.