Development of a small capacity dryer for vegetables

Abstract

High moisture content vegetables undergo microbial attack soon after harvesting/picking. The post-harvest losses of these commodities in developing countries are very high mainly due to lack of storage and processing facilities. The development of processing facilities close to the growing areas is necessary to reduce the losses. The technology for dehydration of vegetables is either traditional or very advanced. Hence the need for an intermediate level technology was realized and an effort was made to solve this problem by developing a small scale dryer. The dryer was tested with different vegetables (cauliflower, cabbage and onion). At a constant air inflow rate of 0·33 m 3/s, it took about 11 h to reduce the percent moisture content dry basis/wet basis from 1260·56 dry basis (92·65 wet basis) to 8·69 (8), 14 h from 1233·33 (92·50) to 8·69 (8) and 12 h from 900 (90) to 8·11 (7·5) with inlet air temperatures of 65, 55 and 56°C respectively for 50 kg batches of cauliflower, cabbage and onion slices. The overall energy utilization efficiencies of the dryer for these vegetables were 30·83, 28·21 and 29·51% respectively. The cost of the dryer was Indian Rs 12000 (US $480) and the estimated costs of processing cauliflower, cabbage and onion slices were Rs 2·16 (US $0·086), Rs 2·76 (US $0·11) and Rs 2·37 (US $0·095) per kg of raw material.