Pulsed vacuum osmotic dehydration of tomatoes: Sodium incorporation reduction and kinetics modeling

• A vacuum pulse diminishes sodium uptake.
• The consideration of variable diffusivity improves the fit of osmotic kinetics.
• The maltodextrin-NaCl solution produced a high water loss, a low NaCl gain, and aw.

Semi-dehydrated food is obtained via osmotic dehydration (OD). The influence of the osmotic agent (27.5% sucrose or maltodextrin combined with 10.0% of NaCl, 40 °C) with/without the application of a vacuum pulse (VP) (100 mbar, 20 min) on the NaCl incorporation and on the kinetics of water loss (WL), solid gain (SG), and water activity (aw) were studied in the OD of sliced tomatoes. The kinetics of the WL and SG were evaluated and fitted with diffusive and hydrodynamic models. The NaCl incorporation was 25% lower in the maltodextrin-NaCl solution (MN) compared to the sucrose-NaCl solution (SN). The MN reduced that incorporation compared to the SN. Moreover, the salt incorporation was significantly reduced (by approximately 50%) by using a VP in the osmotic process, which was independent of the ternary solution. The variable effective diffusivity improved the fitness of the OD kinetics with respect to the constant diffusivity or the modelling of the hydrodynamic mechanism. The large reduction of NaCl incorporation obtained in the present work, which was mainly due to the use of a VP, suggests that more attention is necessary in studies of OD with vacuum pulse involving the immersion of food in a ternary.