In this work, vacuum impregnated apple discs with different isotonic solutions (sucrose and trehalose) were equilibrated during osmotic dehydration (55 degrees Brix glucose at 40 degrees C). Changes in sample composition (water and soluble solid contents), weight and volume are analysed. A mathematical model is proposed to describe and quantify the outflow of water from the protoplast as well as the visco-elastic behaviour of the cell. Good correspondence between simulated and measured data of non impregnated samples and samples impregnated with isotonic solutions of sucrose or trehalose during long term osmotic dehydration is obtained. Fitted values of the cell permeability correspond well with tabulated values. Furthermore, also the obtained values of the parameters describing the mechanical properties of the cell wall and Hectian strands seem to reflect the observed structural development of these structures for the different treated samples well. (C) 2011 Elsevier Ltd. All rights reserved.