Structural and Compositional Profiles in Osmotically Dehydrated Apple

Concentration profiles in apple tissue during osmotic dehydration were studied and compared with simultaneous structural changes. Experiments were conducted in apple slices (20 and 30 mm thick) at 20, 30, 40 and 50°C. After treatments, water and solutes were analyzed in serial slices 1.5 mm thick. The occurrence of an “Advancing Disturbance Front,” (ADF) was proposed to describe the mass transfer. The ADF is located at a distance d_f to the interface, where the reduced driving force (Y) was 0.99. At distances d>d_f (undisturbed zone) neither compositional nor structural changes were observed. Advancing constant rates for the ADF were determined, showing slight temperature dependence. A generalized equation Y=f(d/d_f) described and fitted all the experimental data.