| Popis: |
The osmotic dehydration (OD) is a treatment that reduces partially the moisture content and the water activity of a food. The use of reduced pressure in the first minutes of an OD is called pulsed vacuum osmotic dehydration (PVOD). In PVOD, the expulsion of occlude gases and the entrance of the solution in the food matrix are induced, with consequently mass transfer improvement. In the present work, the influences of independent variables (temperature (T), pressure of vacuum pulse (PV), sodium chloride concentration [NaCl] and sucrose concentration [suc]) on water loss (WL), solid gain (SG), weight reduction (WR), water activity (aw) and moisture content (U) of tomato slices were studied. The optimum condition obtained had its kinetics tested with three models from the literature. The optimized condition (T 40 °C, PV 56.25 mbar, [NaCl] 7.5 % and [suc] 32.5 %) resulted in the maximum values of WL, and WR (42.2, and 36.1 %, respectively) and minimum SG, aw and U (4.0, 0.948 and 76.5 kg water/100 kg sample, respectively). With respect to the kinetics, the best agreement was obtained with the model that considers variable diffusivity. |
