Hot air drying of apple slices: dehydration characteristics and quality assessment

Abstract

The main objectives of the present study were to investigate the drying characteristics and quality attributes of apple slices. The samples were dried at different air temperature levels (50, 60 and 70 °C) and a constant air velocity (1.5 m s−1). It was observed that the drying air temperature affected the dehydration rate significantly. The usefulness of eight different mathematical models to simulate the experimental drying curves was evaluated and the Midilli model provided the best simulation of the samples drying kinetics. The effective moisture diffusivity was determined to be 7.03 × 10−10, 8.48 × 10−10 and 1.08 × 10−9 m2 s−1 for drying air temperatures of 50, 60 and 70 °C, respectively. The shrinkage values of the dried samples at air temperatures of 50, 60 and 70 °C were 74.70, 82.35 and 80.78 %, respectively. The maximum value of rehydration ratio (4.527) and also the minimum value of ∆E (11.27) were obtained for the slices dried at 70 °C.