Freezer burn

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As freezer burn , the occurrence is called dried-surface layers in frozen foods . They are mostly white to gray-brown in color. Freezer burn occurs primarily in areas that are exposed to fresh air, caused by temperature fluctuations or leaky or unsuitable packaging (e.g. parchment paper or cling film). The name comes from the similarity with actually burned places.

causes

Freezer burn (dark) on a piece of beef
Freezer burn (white) on a piece of poultry meat

The main causes of freezer burn are temperature fluctuations during transport in the entire deep-freeze chain, which can hardly be avoided, or temporary failures in cooling, for example due to an unnoticed power failure. If the temperature rises at one point, which also happens when the door to the refrigerator is opened, water begins to evaporate from the layers near the surface. This then condenses or freezes when the temperature drops again to form water droplets and ice crystals on the refrigerated goods and the packaging. This could lead to the products drying out. Frequent temperature fluctuations (switching refrigeration units on and off) and relocation increase the risk of freezer burn in food.

Water is also lost from the food to the surrounding atmosphere through sublimation and the food becomes excessively dry. The water re-sublimates as snow-like crystals in other parts of the food and packaging.

activities

The formation of freezer burn can be prevented by packaging that is as tightly fitting and water vapor-tight as possible (e.g. freezer bags ), by avoiding extreme temperature fluctuations (with the help of technical monitoring) and by glazing the products (meat, fish) with water, which creates a a thin protective layer of ice on the product can be prevented. The discoloration occurs initially due to the sublimation of the ice crystals in the outer layers of the products. This creates cavities that diffuse the incident light and usually make the surface appear brighter. Furthermore, the extreme dehydration leads to a denaturation of proteins and oxidation of fats and other food ingredients. This affects the digestibility and palatability as well as the taste of the affected areas, the food is partially spoiled, although microbiologically harmless. Often it is enough to cut out the affected area.

Since freezer burn is often an indication of temperature fluctuations during storage, attention must also be paid to microbiological processes. Therefore, a temperature of –18 ° C or below should be maintained throughout the cold chain. This is also prescribed in German food law for freezer rooms , for example .

See also

Web links

Commons : Freezer Burn  - Collection of pictures, videos and audio files
Wiktionary: Freezer burn  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c Rudolf Heiss, Karl Eichner: Preservation of foods Chemical, physical and microbiological basics of the process . Springer-Verlag, 2013, ISBN 978-3-662-07666-8 , pp. 154 ( limited preview in Google Book search).
  2. ↑ a b c Ecotrophology . Verlag Neuer Merkur GmbH, 2005, ISBN 978-3-937346-03-8 , p. 237 ( limited preview in Google Book search).
  3. ↑ a b focus.de: From germs to freezer burn - FOCUS Online , accessed on March 15, 2017
  4. ↑ a b Norbert S. Buchner: Packaging of foods Food technology, packaging technology and microbiological basics . Springer-Verlag, 2013, ISBN 978-3-642-58585-2 , pp. 398 ( limited preview in Google Book search).
  5. ↑ gesetze-im-internet.de: TLMV - single standard , accessed on March 15, 2017