Effect of Osmotic Solution Concentration, Temperature and Vacuum Impregnation Pretreatment on Osmotic Dehydration Kinetics of Apple Slices

Abstract

Apple slices of 10mm thickness were osmotically dehydrated with sucrose–water solutions of 0.25, 0.35, 0.45, 0.55 and 0.65 (w/w) at 30, 40 and 50 C. Experimental conditions were atmospheric osmotic dehydration and pulsed vacuum osmotic dehydration, where 180 mbar were applied for the first five minutes. Experimental data were fitted to a mathematical model to obtain the kinetic parameters (De, K, k1, and k2). The influence of operation variables on water, solute concentration and weight net gain is discussed. No significant effect of osmotic solution concentration on effective diffusivity was observed, except with 0.25 w/w concentration osmotic solutions at 30 and 40 C. Under these conditions, the diffusion mechanism seemed to be hindered by some active cell transport due to the mild experimental conditions (low temperature and/or concentration). Vacuum impregnation has a strong influence on weight and solute concentration changes throughout the treatment. The effect of temperature on mass transfer kinetics was well predicted by Arrhenius equation.