Thawing in food industry
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Raw materials (e.g. fish and meat) may be received in frozen state. Thawing will then be needed before further processing is carried out (BAT in the Food, Drink and Milk Industries, June 2005).
2. FIELD OF APPLICATION
Thawing is widely applied in fish and frozen meat processing and it is used in some other sectors such as the production of ready-to-eat meal (BAT in the Food, Drink and Milk Industries, June 2005).
3. DESCRIPTION OF TECHNIQUES, METHODS AND EQUIPMENT
Thawing by contact with the outside environment is slower than the opposing freezing under otherwise equal driving force conditions. Accelerating the thawing by using water saturated hot air may cause a rapid growth of micro-organisms on the surface layers of the thawed product, as well as hindering re-absorption of thawed water, thus creating the unsightly and often nutritionally wasteful drip loss. The use of microwave energy, which is not transferred by conduction through the thawed food layers, is a faster and less damaging thawing process (BAT in the Food, Drink and Milk Industries, June 2005). The traditional thawing of frozen fish and meat takes place under running water. In this case, the unpacked meat or fish are put in iron crates and completely immersed in pools with water. Thawing by sprinkling is also applied. Desalting and defrosting are carried out simultaneously (BAT in the Food, Drink and Milk Industries, June 2005).
4. COMPETITIVE TECHNOLOGIES AND ENERGY SAVING POTENTIALS
- a) Changes in the process
- Avoid hot air use: (BAT in the Food, Drink and Milk Industries, June 2005)
- Thawing using hot air consumes high energy and causes rapid growth of micro-organisms. Other alternative technologies should be used whenever that is possible.
- Use of microwave energy: (BAT in the Food, Drink and Milk Industries, June 2005)
- In a microwave oven the food is heated by passing microwaves through it. The resulting generation of heat inside the food facilitates faster and less damaging thawing. In most cases the consumption of energy is reduced comparing to conventional thawing methods.
- b) Changes in the energy distribution system
- Heat recovery from cooling systems: (BAT in the Food, Drink and Milk Industries, June 2005).
- Recovered heat from cooling systems can be used in the case of thawing deep frozen food. In this case, heat is recovered from cooling equipment and compressors using heat exchangers and storage tanks for warm water. Depending on the cooling system, temperatures in the range of 50-60°C can be achieved.
- c) Changes in the heat supply system
No information is available.
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