Freezing
Storage of frozen products allows kept longer than maintain chilled conditions. Freezing reduces the bacterial decomposition reaction to a very low level, but in the result of structural changes in the product, through the formation of ice crystals. Cells of animal and vegetable products contain water solution of salt and sugar. When this decision starts to freeze the excess water would be frozen until the eutectic mixture is achieved (see Section 12.5). If freezing is not carried out quickly, ice crystals will grow and break through walls of cells; then when the product thaws, the cells will leak and the texture will be spoiled. This is of no great consequence of meat texture that changes when cooking but also fresh fruits and vegetables should be frozen quickly.
Texture and moisture content of the product after thawing will differ from the fresh product, and for some products, it also leads to weight loss in the form of " drip loss". Different methods of freezing are used to minimize these effects.
As a rule, any product that will be eaten without cooking, or only a very brief cooking (for example, green peas, cucumbers, strawberries, beans), should be fast freezing in the blast freezing tunnel or similar device.
Other foods should not be frozen as quickly and placing food in large refrigeration chambers is the most common method of freezing. For meat and poultry are not clearly defined optimal speed of freezing. Many factors such as the quality of the final product (tenderness and taste), weight loss, drip loss, and uniformity of texture were investigated.
The most recent comparison (Sundsten et al., 2001) showed that some of the commercial advantages of fast freezing, but not qualitative benefits. In the process of industrial processing, frozen raw often melt or tempered before into the final product, which subsequently frozen. Meat-based products, i.e. pies, convenience meals, burgers and other, often include meat, which has been frozen in two times. Frozen confectionery products, such as ice cream rely on the speed of freezing to get a certain sequence and structure, and they require special treatment.
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