Developing the Microwave- Hot Air Dryer with Power Density Control System Using Kinetic Modeling of Banana Slice

A microwave-hot air dryer with online microwave power density control was developed for banana slice drying in the present study. This dryer consisted of the online mass measurement, imagining unit, and microwave power control circuit systems. The microwave power control system was set with an Arduino board, SSR relay, and control program in MATLAB environment. Experiments with five levels of fixed power density (4, 5, 6, 7, and 8 Wg-1) were done for examining the kinetics of moisture content and microwave power during the drying process. Also, an image processing algorithm was investigated for measuring the burning percentage of banana slices. For modeling of moisture content kinetics, seven mathematical models were nominated. Results showed that the Logarithmic model could predict the drying kinetics of banana slices better than the other models with the highest R2 (0.9966-0.9831) and lowest RMSE (0.01646-0.02679). Also, the trend of microwave power with time for constant remaining the microwave power density during the drying process such as moisture content variation in all experiments was exponential. Quality evaluation of the final product showed that treatments with power densities of 6, 7, and 8 had 12, 24, and 29% burns, respectively, compared to treatments of 4 and 5 without burns.