ABSTRACT
Osmotic preconcentration is the partial removal of water by direct contact of a product with a hypertonic medium, that is, a high-concentration sugar or salt solution for fruits and vegetables, respectively. During osmotic processing, two major countercurrent flows take place simultaneously. Under the water and the osmotic solute activity, gradients across the product-medium interface, and water flows from the product into the osmotic solution, whereas osmotic solute is transferred from the solution into the product. Based on the desired final product characteristics, the osmotic process may emphasize water removal, solute uptake, or a certain balance between water removal and specific functional solute uptake. Solute uptake during osmotic dehydration modifies the composition and taste of the final product. Optimum level of solute uptake strongly depends on process objectives and desired final product properties. On the process side, the osmotic solute(s) used and especially the molecular size play a very important role.
