Freeze and convective drying of quince (Cydonia oblonga Miller.): Effects on drying kinetics and quality attributes

Abstract

This research aimed to investigate drying characteristics and quality properties of quince subjected to freeze and convective drying at air temperatures of 45, 55, 65 and 75 degrees C. To determine the best drying model for those techniques, nine thin-layer mathematical models were fitted to the experimental results. The statistical analyses revealed that the Two Term, Midilli et al., Diffusion Approach and Two Term Exponential models were better than the other tested models. The results of the color analyses showed that the drying treatments had an effect on the fresh quince samples, and the color of the freeze dried samples was closest to the color values of the fresh samples. The highest rehydration ratio (2.78) was recorded for the freeze dried samples, and the lowest ratio (2.25) was observed in the samples subjected to convective drying at 75 degrees C. Scanning electron microscopy showed that the freeze dried quince samples were only slightly different from the fresh samples and that the disruption of the structure of the quince samples significantly increased as the convective drying temperature increased. Consequently, freeze drying can be an appropriate method for obtaining good-quality fruit samples.