Defrosting (food)

Thawing is normally a slower process than freezing, since the thermal conductivity of frozen tissues is much lower than that of non-frozen tissues. In addition, the formation of a liquid aqueous layer on the surface of the product that is being thawed forms a barrier that keeps the product at 0 °C for a long period, with all the problems that this entails: increased concentration, recrystallizations and increased microorganisms.

To avoid these problems when thawing, companies dedicated to the manufacture of frozen pre-cooked meals prefer products of such a size that they can be cooked directly, without the need for prior defrosting. That is why not all foods need to be defrosted in the same way; Some must do it slowly inside a refrigerator and others do not need it.

Defrost Methods

In general, we can distinguish three thawing methods depending on the use for which the product is intended.

An adequate thawing method allows obtaining good quality food, otherwise the loss of matter (salts, moisture, and other components) means that the products cannot recover their initial characteristics (Normally 100% is not reached). Of course, this also depends on the freezing method previously used (fast/slow, addition of protective substances), which will determine the type of ice crystal formation and the mechanical damage on the cellular structures of the food.

Defrosting-cooking

When the product is defrosted to be consumed immediately, as is the case in private homes or catering establishments. The frozen product is directly cooked. In this method speed and health safety come together. This method is considered to toughen the meat somewhat.

Partial defrosting

When individual frozen portions are made from frozen products. In this case, the product temperature is raised to -5 °C, where 60-70% of the water is still in the form of ice but the consistency of the product allows handling and preparation of the rations. The product is then immediately refrozen.

Defrost-transformation

Complete defrosting is necessary to carry out operations such as deboning poultry carcasses, pieces of meat, etc. without difficulty.

Effects on meat and vegetable products

On these products, a slow defrosting is more advisable to preserve the texture, thus allowing a redisfusion of the water and its return to the initial position.

On vegetables and especially on delicate fruits it is more advisable to force defrost.

Industrial defrosting

In industry, defrosting has the purpose of:

• Proceed to the sale of the frozen product, such as the channels..

• Process the product and then freeze it, like birds.

• Use the product as raw material, such as meat and vegetables.

A long defrosting, of several days, has the drawback of having large facilities and makes it difficult to schedule production based on needs.

The necessary heat to defrost the product can be provided from the surface, by classic procedures or directly from the inside using microwaves