Process of evaporation

Concentration of liquid foods is an important operation of many food processes and there are several technologies available, such as evaporation under vacuum and membrane concentration.

Evaporation has historically been the primary technology for liquid concentration in the food industry.

Evaporation removes most of the water resulting in concentrated product which may be used as such or processed further, e.g. by drying.

Evaporation is employed in the food industry to reduce weight and volume of fluids, with subsequent reduction of packaging, transportation, and storage costs. It also used to reduce the energy consumption at the drying operation.

Another important application is the production of fruit (mainly grape, apple, and orange) and vegetable (mainly tomato products) juice concentration.

In the dairy industry, evaporation is used for concentration duties, such as milk, skimmed milk and whey. It is also used as a preliminary step to drying. The thermal efficiency of evaporators for removing water is much higher (e.g 90%), compared to the efficiency of dryers (e.g. 60%).

Evaporation of water from the solution by heating is feasible, but usually the products to be evaporated are heat sensitive and heating can change some their physicochemical characteristics at this elevated temperature. Evaporation might result in crustal precipitation.

Evaporation might also result in foaming of the concentrate. Evaporation at low temperatures, under vacuum, reduces thermal degradation of food properties (textural and nutritional) and aroma recovery schemes allow collection of essential flavors and aroma compounds.
Process of evaporation

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