ANALYSIS OF THE DRYING PROCESSES OF OSMOTICALLY DEHYDRATED APPLE USING THE CHARACTERISTIC CURVE MODEL

Round slices (2 mm thick) of fresh apple and of apple subjected to osm o-dehydration processes in sucrose syrups until reaching a, values of 0.979, 0.968, and 0.958, were air-dried at 50, 60, and 70 degrees C. A nalysis 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 a, greatly affects the fraction of water lost du ring the drying processes, The use of the Pick's Second Law was not ad equate to describe the experimental drying curves. However, apple dryi ng processes can be modeled by the Characteristic Drying Curve model, using several equations (polynomial and logarithmic) with a high confi dence level. The parameters of each equation showed a great dependence on product's a,. These models can be used to predict drying curves wi thin the studied limits in each case, presenting great advantages when compared to classical models based on effective diffusion coefficient s.