Optimization of Process Parameters for Convective - Microwave Drying of Ashwagandha Roots

Application of microwave for drying of ashwagandha roots was investigated. A laboratory convective microwave dryer was already developed which had the provision of regulating of air temperature, air velocity and microwave power. Ashwagandha roots of uniform size were used in the drying experiment which were carried out at air temperatures of 40, 50 and 60°C, air velocities of 1.0 and 1.5 m/s and microwave power levels of 2, 4 and 6 W/g. Convectivemicrowave drying was accomplished till the moisture content of the ashwagandha roots reduced from initial moisture content of 5.06 kg water/kg of dry matter to a safer level of 0.06 kg water/kg of dry matter. The effect of power level increment of convective -microwave drying was reduced the drying time thereby increased the drying rate. The quality attributes of fresh and dehydrated ashwagandha roots were evaluated for colour changes (L, a, b values), total alkaloids content and rehydration ratio. The samples of sun dried ashwagandha roots were obtained and the quality attributes of this sample was compared with products dried by convective -microwave drying technique. The quality of ashwagandha roots dehydrated by convective -microwave drying was found to be superior to the sun drying process. Page model was found to be best fit for convective microwave drying condition. The process parameters were optimized by using statistical analysis ANOVA for responses with significant model and non significant lack of fit. The optimum operating conditions of ashwagandha roots for power level, velocity and air temperature in convectivemicrowave drying process were 6 W/g, 1.5 m/s and 50°C, respectively and found a good quality of dehydrated ashwagandha roots. Corresponding to values of process variables i.e. 6 W/g, 1.5 m/s and 50°C, the values of rehydration ratio, total alkaloids content, less ΔE were 4.16, 1.94 % and 5.654, respectively.