Modelling of mass transfer during osmotic dehydration of apples

In this study, the osmotic dehydration mechanism of apple slices in different concentrations of sucrose, dextrose and sucrose + dextrose mixed solutions, and also at different temperatures, were investigated. It was recognised that as the concentration and temperature are increased, water loss also increased at a considerable level. It was observed that, in sucrose + dextrose mixed solution having the same total dry matter concentration, both water loss and solid gain increased as dextrose in the mixture increased. The final equilibrium point was estimated using the Azura et al. model (cf. Azuara, E., Cortes, R., Garcia, H. S. and Beristain, C. I. (1992). International Journal of Food Science and Technology, 27, 239-242). By numerical analysis, using Fick's unsteady state diffusion equation, the diffusion coefficients representing water loss and solid gain were calculated. The apparent diffusivity values (by fitting the model to experimental data) were found to be in the range of 10(-10)-10(-11) m(2)/s. (C) 2000 Elsevier Science Ltd. All rights reserved.