Mass transfer during osmotic dehydration of apples

Osmotic dehydration processes are widely applied to obtain high quality intermediate moisture food. The study of dehydration kinetics and mass transfer mechanisms is very important for understanding and controlling the osmotic dehydration process. The internal changes and kinetics of both moisture change and mobility during osmotic dehydration of apples is reported. The effective diffusion coefficient of water was not constant during the dehydration treatment. Initially the effective diffusion coefficient calculated using a Fickian-based model was 2 * 10(-10) m(2)/s and increased to 5 * 10(-10) m(2)/s during treatment. Moreover, results showed the existence of an osmotic dehydration front that moves from the surface to the core of apple samples. It was not possible to explain the osmotic treatment process using only diffusion-based mechanisms. All layers of cells appear to be involved in the moisture transport process at the same time. (C) 2007 Elsevier Ltd. All rights reserved.