Q. What do you mean by Dehydration?

The word dehydration usually refers to the use of controlled conditions of heating, with the forced circulation of air/artificial dryer as compared to the use of sun drying. Dried foods have low available moisture level [low water activity (aw)] so that the microorganisms cannot grow and enzyme activity is controlled. Water activity refers to the amount of unbound or "free" water in a system available to support biological and chemical reactions.

Dehydration processes are used commercially for many foods including dried milk, coffee, tea, fruit mixes, dried fruits, vegetables, meat, fish etc. Although the process of drying lowers water activity (aw) so as to hinder the growth of microorganisms however, this technique of preservation is also requiring certain pre-treatments like blanching and sulfuring. You are already familiar with the term blanching. We shall learn about sulfuring in the next sub-section. Here let us now look at the advantages of drying.

Advantages of drying

Drying has been attributed with advantages of weight reduction, ease of packing, storage and transportation. However, loss of colour, texture and nutritive value has also been observed in this process.