Process of preservation by removal of water

Removal of water and the consequent lowering of water activity constitutes an important principle of food preservations. The removal of water is usually done by drying dehydration, or evaporation.

Although the term are sometimes interchangeably, drying normally refer to the sun drying, or air drying, evaporation refers to drying by the application of artificial heat but under natural draft, and dehydration implies drying by controlling application of application heat with mechanical circulation of air or under a vacuum.

Drying of food involves complete removal of water under controlled conditions in such a way that the food is not altered and results in minimum changes by the drying process. Dried foods contain moisture to the extend of 1-5 per cent and they have storage stability at room temperature of a year or longer.

The term dehydration refers generally to artificial drying under control conditions. However, in modern food processing the term does not refer to all processes that remove water from foods.

Evaporation is the removal by vaporization of part of the solvent form a solution or dispersion of essentially non-volatile solutes. Evaporation is distinguished from crystallization and drying by the fact that the final product is a concentrated dispersion or solution rather than precipitate solids.
Process of preservation by removal of water