ABSTRACT
This chapter discusses the influence of some of the preservation factors on the yield of some of the most typical osmotic processes, for example, candy fruits. Osmotic dehydration (OD) implies three main fluxes in the osmosed food. The uptake of solutes from the osmotic solution and the losses of water and native solutes. OD is conducted separately or in combination with other operations, such as air drying, pasteurization. Different kinds of products imply a different ratio of water loss/external solid uptake, which must define either the operation conditions in OD or the conducting of some sample pretreatment. For pretreatment, different actions can be performed: vacuum impregnation (VI) with external solution or blanching, which will promote solute gain, and coating with edible films, which limits the effect. There are some reasons that explain the heavier weight when VI is applied for short-time processes. All these reasons are based on porous gas replacement by the osmotic solution.
