Diffusion of Water in Chestnut Fruits during Drying and Rehydration Processes at Different Temperatures
Many food materials must be dried in order to decrease its water activity and to increase the shelf-life. Also, rehydration operation must be carried out as previous step before consumption. Both operations are commonly employed in some industrial chestnut processing. These processes can be carried out at different temperatures and in all cases the quality of the final product can be affected. In this work, convective drying with hot air is the employed method for water removal and rehydration is carried out by immersion of chestnut in water. In both cases, mass transfer processes are governed by water diffusion in the bulk of the solid. The aim of this work is to determine experimentally the drying and rehydration kinetics of chestnut samples at different conditions of temperature and moisture content. Obtained data are modeled with a diffusional model taking into account volume variations and the corresponding values of the coefficients of diffusion of water are obtained. Analysis of the results indicates that drying/rehydration rates increase with temperature and rehydration kinetics are also depending on the initial moisture content of chestnut. Finally, leaching flow during rehydration is only important at high temperature due to starch gelatinization processes.
Andreas Öchsner and Graeme E. Murch
R. Moreira et al., "Diffusion of Water in Chestnut Fruits during Drying and Rehydration Processes at Different Temperatures", Defect and Diffusion Forum, Vols. 273-276, pp. 758-763, 2008