ABSTRACT
Drying of foods, particularly solid foods, was perhaps the oldest and cheapest method effectively practised in the early age of human civilization for the extension of shelf life. Further, they understood two prime factors required for carrying out the drying – energy to reduce moisture and the large surface area. The modern drying technique is now based on thermodynamic aspects of water and food interactions. The energy associated with the water present in food is conveniently explained in terms of water activity. The technological advantages of drying operation are ease of handling, packaging and storage, whereas the economical advantage is cost reduction in handling of reduced mass and volume of the dehydrated materials. Drying is an energy-intensive process. The dryers used in drying of foods can be classified as batch dryers and continuous dryers. A modification of tray dryer employed for large-scale drying is tunnel dryer. Belt dryer can also be applied for drying of liquid foods.
