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Monday, January 6, 2020

Freezing( slow freezing,Rapid freezing and Advantages and disadvantages)

Freezing (slow freezing, Rapid freezing , Advantage and disadvantages)
Introduction:
  The Freezing process is one of the most important process or method and most commonly used processes or technique that can be use as commercially and domestically for preserving a very wide range of food products including prepared many  food products  which would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but the potatoes itself require only a cool dark place to ensure many months storage.

The Freezing processing makes water unavailable to microorganisms. The chemical and physical reactions leading to deterioration or spoliage are slowed by freezing. The many White patches on frozen food caused by water evaporation in  the packages air spaces which called freezer burn occurs because of these they causes deterioration of taste and appearance in many food products.

 This is mainly occurs in some  fruits, vegetables, meat, poultry and fish etc. While in  many home freezers are held at -10°C, commercial freezers are under -18°C. At this temperature, the growth of microbes is almost stopped . The microbial retardation reactions will still occur but it over a much in longer time.

In addition, the deteriorative or enzymatic reactions will still take place during  storage of forzen. The Uncooked fruits and vegetables must be blanched before freezing to preserve these reactions. During freezing process, the water in food forms ice crystals. The rate of this crystal has a big impact on the quality of frozen foods:

Slow freezing:

The Slow freezing process such as best  example is home freezer; forms a  large ice crystals which puncture cell walls and cellular fluid is released and also results in shrunken appearance of thawed food. In this process the freezing is don within  3-72 h. This method mainly  used in home freezer and temperature is lowered to -15 to -29°C.

Rapid freezing:

During the rapid freezing process  small, numerous ice crystals are formed and cell structure is not changed. In this process the temperature of food is lower to about -20°C within 30 min. This process blocks or suppresses the metabolism.The shelf life of frozen foods is mainly dependent on the storage conditions.
 The ideal conditions of  frozen foods can have a shelf life of one year. However, if foods are continuously exposed to warmer temperatures, such as the opening and closing of freezer doors, then heat shock will be occurs. The Heat shock  is occur  when the  ice melts and re-forms into larger ice crystals. The best example of heat shock  is ice cream, which has a gritty texture if large ice crystals have developed.

Advantages and disadvantages:
Advantages:
The main Advantages of freezing are generally good retention of nutrients and inhibit the  microbial growth by low temperature and unavailability of water.
Disadvantages:
The main disadvantages  of freezing process or method are loss of some of the  B-Group vitamins and vitamin C due to its  blanching of vegetables prior to freezing and unintended thawing can reduce their product quality. 

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