Experimental studies on thin-layer drying of mint leaves in a solar dryer and under open sun

Thin layer drying behaviour of mint leaves was experimentally studied using a domestic, direct-type, natural convection solar drying unit and compared with traditional open sun drying. The experiments were conducted in Bengaluru (12.96°N, 77.56°E), Karnataka, India and the effect of various parameters on drying was studied. Drying time using the solar drying unit was compared with traditional open sun drying. Reduction in drying time was found using the solar drying unit compared to open sun drying. After 10 h, the moisture in the mint leaves was observed to reduce from 93% to 8.33% in the solar drying unit and to 26.6% under open sun drying conditions. The drying data were analysed and curve-fitting was done using five thin-layer drying models. Among these models, logarithmic model for solar drying unit and the Henderson and Pabis model for open sun drying were found to satisfactorily describe the drying kinetics of mint leaves.