A study of the mass transfer in osmotic dehydration of coated potato cubes

Abstract

This study investigated the coupling of edible coatings with osmotic dehydration of potato cubes under various process conditions. Solutions of 1% sodium alginate and 2% low methoxyl pectinate (LMP, degree of esterification: 31.5%) were chosen as the coating materials and NaCl was used as the osmotic agent to study the mass transfer behavior during osmotic dehydration of potato tissues. Potatoes were cut into cubes of 1 cm3 and coated with the coating materials. Calcium chloride solution of 1% or 2% was used as the cross-linking agent. Salt concentration of 10%, 14% and 18% and temperature of 25, 40 and 55 °C were used as the process variables to investigate the kinetics of water loss and salt uptake. Modeling of the mass diffusion and its kinetics were carried out to better understand the mass transport phenomena in potatoes with coatings and to determine the efficacy of the coupled system. Mass transfer kinetics was modeled by using Peleg's proposed equation and the effect of process variables on the model parameters was studied. Diffusivities of both water and solute were evaluated by using Crank's analytical solution to Fick's second law. These two models could well describe how the considered variables influenced the mass diffusion and kinetic rate constants during the osmotic dehydration of both non-coated and coated potatoes. © 2005 Elsevier Ltd. All rights reserved.