Moisture diffusivity and drying kinetic equation of convective drying of grapes

The aim of this work is to evaluate experimentally the drying kinetics of agricultural products as a function of drying conditions and to evaluate the diffusion coefficient. The study is performed on two kinds of grapes grown on both sides of the Mediterranean sea. Two models of diffusion have then been performed to evaluate the effective diffusivity. A simplified one based on Fick's law and a second one that takes account of the shrinkage as a fundamental parameter by modeling the movement of dry solids and the consequent movement of the bound substance. A comparison is then made between the results obtained for the two considered varieties as well as between our results and those found in literature. The drying kinetics are linked to the experimental conditions by means of two parameters K and N. A regression analysis based on Fick's law determined the dependence of these parameters on drying conditions for each variety of grape. (C) 2002 Elsevier Science Ltd. All rights reserved.