Modeling of Mass Transfer in the Drying Process of Apple Slices Using Infrared Irradiation with Intermittent Heating Method

Infrared radiation by intermittent heating is a novel method in which the surface temperature of the product is maintained at a constant value. This method is widely used in simultaneous blanching and drying process. The main advantages of intermittent IR-radiation are energy saving and preventing undesirable quality changes in the final product. The calculations of mass transfer in this process can be used to estimate the temperature and time conditions in the process. For this purpose, drying behavior of apples slices (Golden Delicious variety) was investigated with slab shape in three different sizes: thickness of 5, 9 and 13 mm and length and width was 20 mm. Heating operation performed by infrared dryer that was equipped with controller of product surface temperatures at 70, 75 and 80 °C. Kinetic models such as Newton, Page, Modified Page, Henderson-Pabis and parabolic were fitted on experimental data of dimensionless moisture ratio using MATLAB software. The adjusted correlation coefficient (Adj.R2) and root mean square error (RMSE) were used to compare the models. The evaluation of effective moisture diffusivity (Deff) performed during drying of slices and its dependency with temperature investigated using Arrhenius equation. The results showed that models of page and parabolic presented a good fit on experimental data, respectively (higher Adj.R2 and lower RMSE). The effective diffusion coefficient significantly elevated with an increase in surface temperature and thickness. This parameter showed higher energy activation for lower thicknesses that indicated a greater irradiation temperature dependence of effective diffusion coefficient through the decreasing of thickness.