Effect of microwave, infrared and freeze drying methods on drying kinetics, effective moisture diffusivity and color properties of turmeric

Abstract

In the present research, effect of methods that use the microwave (90, 160 and 350 W), infrared (60, 70 and 80 °C), and freeze drying for turmeric samples on the drying kinetics, effective moisture diffusivity and color were analyzed. Also ten distinct thin layer models of drying were used to predict their kinetics. Depending on the evaluation of the statistical tests, models of Midilli et al and Wang & Singh models were found the optimum ones for explaining drying characteristics of turmeric. Among the used methods, the fastest and slowest drying time was 65 min with microwave drying (350 W) and 600 min with freeze drying, respectively. The calculations demonstrate that the maximum effective moisture diffusivity value is obtained in microwave drying (350 W). Our study shows that although the freeze-drying increases the drying time, it showed closest color results against to fresh samples. In conclusion, microwave, infrared and freeze drying methods applied to turmeric should improve with the combined drying applications.