Effects of pulsed electric fields assisted osmotic dehydration on freezing-thawing and texture of apple tissue

The effects of pulsed electric fields (PEF) assisted partial dehydration of apple tissue on freezing-thawing processes and texture characteristics were studied. The apple disks were treated to a high level of tissue disintegration (electrical conductivity disintegration index Z was ≈0.98) and then were subjected to osmotic dehydration (OD) in the apple juice-glycerol solutions using different concentrations of glycerol and time of dehydration. PEF-assisted OD resulted in noticeable acceleration of the freezing/thawing processes as compared with those for untreated samples. The main characteristics of freezing-thawing processes (freezing and thawing time and freezing temperature) and texture of samples in dependence on intrinsic moisture content in the sample were evaluated. The differences in these characteristics were explained by the differences in spatial distributions of soluble solids and water inside the samples. For some optimum parameters of osmotic treatments (e.g., at t = 180 min, C ≈ 20 wt. %), the texture after defrosting was comparable to that of fresh apples.