The thin layer drying characteristics of organic apple slices

In this research, the organic apple slices were dried as single layer with thicknesses of 5 and 9 mm in the ranges of 40–60 °C of the drying air temperature in a convective hot air dryer. The effect of drying air temperature and slice thickness on the drying characteristics and quality parameter of the dried apple slices were also determined. It was found that apple slices would dry perfectly within 240–460 min under these drying conditions. The transport of water during dehydration was described by applying the Fick’s diffusion model and the effective diffusivity changed between 2.27 × 10−10 and 4.97 × 10−10 m2/s. A non-linear regression procedure was used to fit 10 thin layer drying models available in the literature to the experimental drying curves. The models were compared using the coefficient of determination, mean relative percent error, root mean square error and reduced chi-square. The logarithmic model has shown a better fit to the experimental drying data as compared to other models. The effect of the drying air temperature and slice thickness on the drying model constants and coefficients were also determined.