Mathematical Modeling of Microwave-Assisted Foam-Mat Drying of Kefir

Abstract

Kefir is a traditional drink produced by the fermentation of milk with kefir grain. In this study, foam-mat drying of kefir using a microwave oven was made, and drying kinetics was determined at various microwave power levels (100, 180, and 300 W). Values of $D_{\text{eff}}$ were calculated between $4.8394\times {10}^{-10}$ and $1.8603\times {10}^{-9}$  m2 s-1. Besides, $E_{\text{a}}$ was calculated as 5.28 W g-1. Furthermore, increased drying rates were obtained with increasing microwave powers. In addition, seven drying models were fitted to the moisture ratios obtained from experiments, and Midilli and others’ model was found to be the best-fitted model with the highest values (0.9983, 0.9983, and 0.9985 for 100, 180, and 300 W, respectively) of $R^2$ and the lowest values of ${\chi }^2$ , RSS, and RMSE.