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Frozen fish , here at a stall in Riga's central market
Freezing bread in a home freezer

Freezing is a gentle technique for preservation of food . The terms “deep freezing” or “deep freezing” are used for industrial processes, cold preservation in the domestic freezer is called “freezing”. The removal of heat through product-specific, rapid shock freezing and the resulting halted growth of microorganisms means that frozen foods can be stored for several weeks, some even for a year. The loss of vitamins and nutrients is very low compared to other preservation methods, even after months. Many foods, especially vegetables and meat, are blanched before deep-freezing .

In 2008, ready-made meals (293,238 tons), frozen vegetables (291,343 tons) and frozen pizzas (237,979 tons) were sold most frequently in German retail .

Physical processes

Due to the low temperatures, the liquid freezes in and between the cells of the food. The microorganisms that cause aging can barely multiply. In industrial deep freezing, the particularly fast shock freezing prevents the formation of larger ice crystals that can break up the cell structures. This is a major difference from freezing in your own freezer. When storing the food, it must be hermetically sealed to prevent freezer burn .

Especially when freezing slowly, as is the case with most conventional freezers, large ice crystals form, which affect the cell structure of the frozen food. Therefore, microorganisms can multiply much faster in thawed foods than in fresh products. However, if thawed products are cooked or heat-treated, they can be frozen again without hesitation.

Food law and re-freezing

In matjes in the Dutch Food Law, a freezing at -45 ° C is prescribed to infestation by nematodes exclude that are reliably killed at this temperature.

Ready meals are partly processed in the frozen state. Fish fingers are sawn out of frozen plates of fish fillet and coated with breadcrumbs under brief heating without the fish thawing.

Industrially produced frozen products ( frozen food ) must have a maximum temperature of −18 ° C at all points after thermal stabilization (completion of the freezing process). A closed cold chain must be ensured when transporting frozen products. Section 2 (4) of the Ordinance on Frozen Food (TLMV) stipulates that short-term deviations of a maximum of 3 ° C are permitted for shipping, local sales and in the retail freezers “within the framework of honest storage and distribution procedures”.

Within the European Union, the packaging of frozen food must bear a notice that the product must not be frozen again after it has been thawed . But this is mainly a security measure. Its purpose is to prevent consumers from storing thawed frozen food in a warm place for too long before freezing it again. Because aging starts again after thawing and thus leads to the growth of microorganisms, which influence the quality and greatly reduce the printed best- before date .

See also


  1. Wirtschaftswoche , edition 13/2009, p. 13

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