Study of compositional and structural profiles in dehydrated apple tissue (var. Granny Smith).

摘要

In this work an attempt is made to analyse how the concentration profiles evolve in osmotically dehydrated apple tissue. Apple slices, 30 mm thickness, were subjected to osmotic dehydration with sucrose solution (45 and 55 B), at 20, 30, 40 and y 50°C. After treatments, water and solutes profiles were analysed from a pseudodiffusional approach (PDA) and with a model based on the “advancing disturbance front” (ADF). ADF has been defined as the virtual plane that separates the zone of the tissue near the interface where the original concentration status has been disturbed by the osmotic process from the rest of the tissue where no changes in concentration or mass fluxes are evident. The Disturbance Front Model (DFM) equations, based on the ADF concept allow us to predict sample concentrations during osmotic treatment as a function of some characteristic parameters. Analytical concentration profiles were also contrasted with microscopic observations. The two zones mentioned above could be appreciated in the micrographs. The first zone, A, with evidently structural changes, was found near of interface and another one, B, non-affected for the treatment which cells show fresh aspect.;The aim of this work is to check the ADF model in osmotically dehydrated apple when a lower osmotic solution (OS) concentration than those previously studied. The simultaneous structural changes observed by Cryo-SEM throughout the sample thickness before the FDP status is also analysed. In conclusion, the results show that the parameters from the Disturbance Front Model allows us described the mass transfer phenomena, not only at kinetic level, more us, at structural level. The advancing front rate is function of the temperature and a quickly perturbed distance in the tissue is evident in micrographs from near of interface zones.