14A-6

C. O. FERNANDEZ¹, G. Mazzanti², and M. Le Maguer¹. (1) Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada, (2) School of Engineering, U of Guelph

Osmotic dehydration facilitates water loss and solids gain across the semipermeable membranes of the food. Due to the complexities of the process and the nature of the plant materials, the mass transfer behavior of plant tissues has been difficult to understand. To understand this behavior further, the kinetics of water loss and solids gain has to be measured and described.

The objective of the study was to develop a simple method to characterize the mass transfer behavior of apple tissues during osmotic dehydration.

Apple slices were subjected to osmotic treatments using sucrose of varying concentrations from 10 to 60% (w/w). Samples were taken at different treatment times from 15 to 180 minutes. Water loss was determined by measuring the moisture content of the slices. Solids gain was determined by measuring sucrose content with high-performance liquid chromatography. An adapted model using inverse polynomial was used to fit the water loss and solids gain kinetics data. The model was also used to develop a method to describe fluxes of mass transfer during the process.

The inverse polynomial model fitted the kinetics data very well. Using this model and by considering the geometry of the samples, the rates and fluxes of mass transfer of water and solids can be described at each concentration. Results showed that the rate of water loss or solids gain is not directly related to concentration. Very high (60%) concentrations, for example, do not always give the fastest rates of mass transfer.

Results of the study have given a number of descriptions of the behavior of apple tissue during osmotic dehydration. The method of characterization that was developed was simple and flexible that it can be easily applied to water loss and solids gain kinetics data of other plant materials.