STRUCTURAL AND COMPOSITIONAL PROFILES IN OSMOTICALLY DEHYDRATED APPLE

Concentration profiles in apple tissue during osmotic dehydration were studied and compared with simultaneous structural changes. Experiment s were conducted in apple slices (20 and 30 mm thick) at 20, 30, 40 an d 50 degrees C. After treatments, water and solutes were analyzed in s erial slices 1.5 mm thick. The occurrence of an ''Advancing Disturbanc e Front,'' (ADF) was proposed to describe the mass transfer. The ADF i s located at a distance d(f) to the interface, where the reduced drivi ng 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 depende nce. A generalized equation Y=f(d/d(f)) described and fitted all the e xperimental data.