Performance Evaluation of Hybrid UV-A and UV-C Dehydrator for Enhancing the Shelf Life of some selected vegetables

Abstract

Postharvest losses of vegetables remain a major challenge in tropical regions due to high moisture content and microbial spoilage. This study evaluated the performance of a laboratory-scale hybrid UV-C/UV-A dehydrator as a non-thermal preservation technology for onions, okra, and tomatoes. The system integrated ultraviolet irradiation with controlled convective drying to enhance microbial inactivation and moisture removal at moderate operating temperatures. Under loaded conditions, average UV-C and UV-A doses of 570 mJ cm⁻² and 8,100 mJ cm⁻², respectively, were delivered uniformly across the tray surface. The dehydrator achieved moisture reductions exceeding 84% for all vegetables, with final dried masses of 0.55 kg (onion), 0.65 kg (okra), and 0.40 kg (tomato) from an initial 5 kg batch. Drying was achieved under stable thermal conditions, demonstrating efficient energy utilization. During 48 days of ambient storage, UV-treated samples maintained approximately one log-cycle lower microbial load than untreated controls and remained within acceptable microbiological limits, confirming significant shelf-life extension. Vitamin retention ranged between 75–90%, exceeding typical values reported for conventional hot-air drying. The results demonstrate that combined UV-C/UV-A dehydration provides an energy-efficient, nutrient-preserving, and scalable alternative to conventional thermal drying for postharvest vegetable preservation in resource-limited settings.