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

What are the changes during food processing?

Chemical changes that occur during food processing are numerous, and they can be desirable, undesirable of questionable consequence or a combination thereof.

Chemical changes that occur affect its overall quality and may influence both its major and minor components and sensory attributes.

Browning reactions may be caused by enzymatic oxidation of polyphenols and other susceptible compounds if the oxidizing enzymes are not activated.

Advantages that might be attained due to processing of food might relate to reduction in its content of hazardous anti-nutrients such as enzyme inhibitors, cyanogens, glucosinolates, among others as well as control of microbial and enzymatic spoilage.

The major disadvantages of food processing are:
*harm to the sensory properties and nutritive value of some foods, particularly when severe methods of processing are applied to tissues of foods.
*development during some kinds of processing and handling of new chemicals that must be classed as toxicologically undesirable.

The two major chemical changes that occur during the processing and storage of foods, leading to deterioration in sensory quality are lipid oxidation and non-enzymatic browning.

Chemical reactions are also responsible of changes in the color and flavor of foods during processing and storage.

All the changes including chemical, physical, biological, nutritional and sensory, can be measured, so their progress during processing can be followed.

The progress of processing can be measured un many ways, such as chemical analysis, physical measurements, counts of microorganism and color, texture and flavor assessments by sensory panels.
What are the changes during food processing?