Drying
Drying is the preservation of food by air drying . The term is derived from the kiln , the grid-like device that has been used for drying since ancient times.
Drying is probably the oldest method of preservation. Nowadays, faster drying processes such as freeze drying or spray drying are mostly used for industrial applications . Drying is therefore mainly used to dry smaller amounts of food in an agricultural or household setting.
Principles
The aim of dehydration is dehydration, i.e. to remove as much water as possible from the food. This deprives the microorganisms that cause spoilage of their livelihood and extends the shelf life of the food. Most types of bacteria no longer multiply when the water content is less than 35 percent. Many molds, on the other hand, are still decomposing up to a water content of 15 percent.
During dehydration, the dehydration takes place by the fact that dry, warm air flows past the food. The moisture layer on the surface of the food evaporates in it. Water flows in from the inside of the food, which evaporates again on the surface until the water content of the food is too low for further flow. The moist drying air is discharged into the environment.
Drying temperature and time
In contrast to sterilization , heating does not kill the microorganisms, only dehydration. The higher the temperature of the drying air and the greater the permeability of the fabric of the food and its surface area, the faster the drying process. The temperature must not be too high either, because heat can destroy valuable ingredients and trigger undesirable chemical processes (e.g. browning ). Too low a temperature, on the other hand, delays the drying process and gives the putrefactive agents too much time to attack the food to be dried.
For fruits, vegetables and mushrooms cut into slices or wedges, temperatures between 30 and 70 ° C are suitable, depending on the type of fruit, in order to achieve a degree of dehydration of 25 to 50 percent after a drying time of 6 to 12 hours. Grains (maize, cereals, seeds, kernels, nuts) can reach a degree of dehydration of 80 to 90 percent after four to six hours of drying. Herbs can be dried in ambient air for two to three weeks, or in a microwave oven in about two minutes.
Advantages and disadvantages
Compared to other preservation methods, drying has the advantage that the food becomes smaller and lighter when dehydrated, which makes it easier to transport and store. The vitamins, minerals and dietary fibers of the dehydrated food are retained. Dehydration can change the taste and consistency of food, opening up new uses.
One of the disadvantages of drying is that it does not kill the putrefactive agents and therefore only delays spoilage. Depending on the method, it is also associated with a relatively large amount of time and / or energy.
Drying process
The easiest way to dry food is to expose it to the dry ambient air. It is to a dryer ( kiln ) or in the Palatinate traditionally in a wicker basket (fruit nurseries, Hoertel) set or strung on a string. The drying room must be free of dust and have good air circulation and low humidity. Because drying takes a long time at ambient temperature, the food to be dried must be turned over regularly and checked for mold growth.
Air drying can also take place in a specially designed drying cabinet in which dryer fabrics are used. The drying capacity can be increased by using a heat source and / or a fan on the floor. Sun dryers are drying cabinets that use the heat of the sun's rays for drying.
Food can also be dried in the oven . It is placed on grids lined with baking paper. The moisture escapes through the open oven door.
There are also dehydrators for household use. They consist of a heating element and a fan that blows the heated air upwards through the drying sieves, which are stacked on top of one another and covered with food to be dried.
Food that can be dehydrated
.jpg)
The foods that can be preserved by dehydration include:
- Fruit ( dried fruit ), in slices or pieces, with or without peel; or as dried fruit puree (fruit paste, fruit leather ).
- Vegetables, in particular cabbage, onion and root vegetables, in slices or pieces
- Mushrooms ( dried mushrooms ).
- Herbs
- Grains, kernels and nuts.
- Meat ( dried meat , smoked meat )
- Fish ( stockfish , clipfish )
Storage of food to be dried
Dehydrated food contains 10 to 15 percent residual moisture. In order to prevent spoilage, especially the formation of mold, it must be packed airtight and moisture-tight, and stored in a dark and cool place. Commercially produced dried fruit is often also sulphurized to extend its shelf life .
The dried fruit moth ( Plodia interpunctella ) is a pest that attacks dried fruit . Other pests that feed on dried material are grain moths , grain and bacon beetles , rats and mice.
Use of food to be dried
Dehydrated food can be consumed immediately or used in dishes instead of non-dried food. To do this, depending on the recipe, it is necessary to soak vegetable dehydrated food or especially dried mushrooms for a few hours in water in order to restore the moisture that has been removed from the dried food.
Fruits, mushrooms and herbs can be crushed to powder after drying and used as a condiment or as a base for liquid food (e.g. soups, shakes).
Many healthy snacks can be made from dried foods, including gently dried apple, banana or low-fat vegetable chips . Dried fruits can also be used in baked goods or in muesli.
swell
- Achim Samwald: drying: fruits, vegetables, herbs ; Ulmer Verlag, 4th edition 2007, ISBN 978-3-8001-4922-3 .
Individual evidence
- ↑ Samwald, pp. 9-10.
- ↑ Samwald, p. 24.
- ↑ Samwald, p. 11.
- ↑ Samwald, pp. 12-13.
- ↑ Samwald, pp. 15-18.
- ↑ Samwald, p. 15.
- ↑ Samwald, pp. 18-21.
- ↑ Samwald, pp. 25-26.
- ↑ Samwald, p. 26.
- ↑ What can you dry everything? Creative ideas to do yourself . In: For Your Health . March 26, 2018 ( foryourhealth.de [accessed July 17, 2018]).