Analysis of the Drying Processes of Osmotically Dehydrated Apple Using the Characteristic Curve Model

Abstract

ABSTRACT Round slices (2 mm thick) of fresh apple and of apple subjected to osmo-dehydration processes in sucrose syrups until reaching aw values of 0.979, 0.968. and 0.958. were air-dried at 50. 60. and 70°C. Analysis of the drying curves showed that the products do not present a constant rate period (except for fresh apple) but showed two falling rate periods. Initial aw greatly affects the fraction of water lost during the drying processes. The use of the Fick's Second Law was not adequate to describe the experimental drying curves. However, apple drying processes can be modeled by the Characteristic Drying Curve model, using several equations (polynomial and logarithmic) with a high confidence level. The parameters of each equation showed a great dependence on product's aw These models can be used to predict drying curves within the studied limits in each case, presenting great advantages when compared to classical models based on effective diffusion coefficients.