Drying (food)



Drying is a method of food preservation that works by removing water from the food, which prevents the growth of microorganisms and decay. Drying food using the sun and wind to prevent spoilage has been known since ancient times. Water is usually removed by evaporation (air drying, sun drying, smoking or wind drying) but, in the case of freeze-drying, food is first frozen and then water is removed by sublimation.

Bacteria and micro-organisms within the food and from the air need the water in the food to grow. Drying effectively prevents them from surviving in the food. It also creates a hard outer-layer, helping to stop micro-organisms from entering the food.

Food types
Many different foods are prepared by dehydration. Good examples are meat such as prosciutto (a.k.a. Parma ham), bresaola, and beef jerky. Fruits change character completely when dried: the plum becomes a prune, the grape a raisin; figs and dates are also transformed. Drying is rarely used for vegetables as it removes the vitamins within them, however bulbs, such as garlic and onion, are often dried. Also chilis are frequently dried.

For centuries, much of the European diet depended on dried cod, known as salt cod or bacalhau (with salt) or stockfish (without). It formed the main protein source for the slaves on the West Indian plantations and was a major economic force within the triangular trade.

Drying began around 4,000 B.C.

Dried and salted reindeer meat is a traditional Sami food. First the meat is soused. It is kept in saltwater for a couple of days to guarantee the conservation of the meat. Then the meat is dried in the sun in spring when the air temperature is below zero. The dried meat can be further processed to make soup.

Methods
There are many different methods for drying, each with their own advantages for particular applications; these include:


 * Bed dryers
 * Fluidized bed dryers
 * Shelf dryers
 * Spray drying
 * Sunlight
 * Commercial food dehydrators
 * Household oven