Abstract

• Solar energy, a form of sustainable energy, has been claimed as a great potential for drying of fruits and vegetables since it is naturally accessible. Solar dryers using natural convection or forced convection are used for drying of agricultural products. In this research, white radishes were dried by distributed solar cabinet dryer (DSCD), forced convection solar cabinet dryer (FCSCD), Tray Dryer (TD) and by sun drying (SD). The dryers were fabricated by locally available materials such as plywood, corrugated galvanized iron sheet and glass. The dry bulb and wet bulb temperature ( oC), relative humidity (%) and rate of drying (g/hr. sq.cm) were determined as drying characteristics during the drying process. A rather effective of solar radiation in lowest tray of DSCD and FCSCD was observed. The effects of four drying method on the physicochemical properties and nutritional values, minerals and heavy metals constituents and rehydration ratios of dried white radishes were investigated and compared with fresh and commercial products. The determination of water activity and microbial load were examined to extend the shelf-life of dried products. The organoleptic properties of rehydrated white radish were also determined by 9-point Hedonic Scale Rating Test. The findings suggested that the commercial scale use of DSCD for drying of vegetables during off-season.