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Disadvantage of food - Food thawing disadvantage

Technical information Food refrigeration and freezing Thawing Of Frozen Foods

Chilled Food

Superficially, the defrosting cancellation freezing (energy enters the food to melt the ice crystals). However, defrosting of the more complex operation than freezing (and, unfortunately, remains mainly on the consumer, the end of the supply chain). Thawing difficult and requires care for three reasons:
  • Thawing creates a region that has a lower thermal conductivity than even frozen products, thereby preventing the heat flow
  • The external environment (or energy source) cannot create as big temperature changes (or gradient), as possible without freezing cooking in the period of thaw
  • During thawing, there is a high risk of microbial growth of temperature/times allowing the growth of bacteria.
Emerging thawing method that has no limitation (2) press shift thawing (Cheftel etal., 2002): melting ice (form III) at temperatures below 15C under high pressure (200 to 400 MPa), which is used to circumvent the difficulties in conventional melting, such as exposing the surface of the products at temperatures above 0C.

Defrosting is carried out on an industrial scale is a step in the processing of semi-finished products, food materials.

However, most of the frozen products finally thawed home, shortly before consumption. Thus, ironically, defrost, which is perhaps the most difficult operation of the whole chain of operations for the production of frozen food products, ultimately, to the left to the consumer, the appeal process can negate all the care and strict quality control of the frozen products of the technological process. Freezing does not kill microorganisms and, consequently, the basic rules to avoid spreading germs defrost chill temperatures, in a home refrigerator.

While cooking, so maybe sometimes in combination with heating in the oven (either conventional or microwave), if dehydration prevent surface. If it is possible to divide a piece of frozen food into smaller pieces (for example, individual pieces of bread sliced bread), heat transfer speed is four times for each twice the thickness. This follows from the solution of the heat equation.

Defrosting in the microwave oven has the disadvantage is that electromagnetic waves are preferentially absorbed in a frost-free (thawed) food. Defrost by ultrasound (internal thawers were developed in Japan), in principle, better than defrosting in the microwave oven, because ultrasound absorbed in compressible frozen region (Miles et al., 1999). Good contact between the food and ultrasonic source must be provided by immersion in water, therefore, it is suitable only for wet products of the correct form, which is a disadvantage also thawed electric current (resistive heating)...

 
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