Economic Optimization of Drying Apple Slices by Response Surface Methodology

Apple is a valuable agricultural product that can be dried in the form of slices to create much added value in the economic landscape. In the present research, a laboratory hot-air channel dryer was employed for economic optimization of the drying process of red apple slices by means of response surface methodology (RSM). In the RSM technique, by designing experiments in which all independent parameters are changed simultaneously, the simultaneous effect of all parameters on the test output(s) was determined which provided a complete picture of how the parameters affect the test output for the researcher. For designing the experiment by means of RSM in this research, two parameters of temperature and velocity of air passing through the dryer channel were selected as independent variables and two parameters of drying time and energy consumption were chosen as target (response) variables for optimization. In order to design the experiments by RSM approach, the central composite design (CCD) method was used. Finally, by performing pre-designed experiments and using analysis of variance (ANOVA), the optimal drying conditions of red apple slices were determined as the passing air temperature equal to 70 °C and the passing air speed equal to 3 m/s, where the amount of energy consumption and the drying duration of validation test were 1.51 kWh (in comparison to predicted value of 1.36 kWh) and 46 minutes (in comparison to predicted value of 41 minutes), respectively.