Optimization of microwave apple drying using response surface method

Abstract

In this study, the effects of microwave output power and slice thickness on microwave drying of apple slices were studied by using response surface method (RSM) in a modified domestic microwave oven. For experimental design, the central composite rotatable design approach was used. The values of response variables, effective diffusion coefficient, drying rate constant, color change, Hue angle, total drying time and energy consumption, were determined from the experiments performed under design conditions. It was seen that the obtained second order polynomial equations successfully represent the response variables. The results of analysis of variance (ANOVA) and response surface curves revealed that microwave output power and slice thickness were significantly effective on response variables. The effects of the independent variables on the responses and the significance level of these effects were evaluated statistically and the optimum drying conditions were determined for the aims of min color change, total drying time, energy consumption and max Hue angle. Verification experiments were performed with a maximum of 9.54% error at the recommended optimum test conditions. It has been shown that the response surface method can be successfully applied in the microwave drying of apples.