Theoretical Analysis of the Shrinkage Deformation in Viscoelastic Food during Drying

Abstract

Shrinkage of biological materials during drying takes place simultaneously with moisture diffusion and may affect the moisture removal rate. Hence, the drying model considering of shrinkage phenomena is important for the estimation of the drying rate and design of driers. In this study the objective is to develop a drying model that takes into account shrinkage deformation in visoelastic food accompanying changes in moisture content. Using drying potato sample formed cylindrically, the elasticity and viscosity coefficient were obtained with a stress-relaxation experiment by a generalized Maxwell's model. A model of simultaneous heat and moisture transfer in a cylindrical sample was coupled with the virtual work principle applicable to a body undergoing shrinkage deformation. Nonconstant physical and thermal properties were also incorporated in the model. Governing equations and boundary conditions were solved numerically using Galerkin's finite element method. Comparison between experimental results and predicted ones provides satisfactory agreement. © 2002, Japan Society for Food Engineering. All rights reserved.