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Thawing Frozen Food: Best Practices 
 

   

Thawing Frozen Food: Best Practices

Dr.Hamid Ragab Hamid

B.V.Sc.; M.Sc.

Meat Inspection Unit, ADFCA

E-mail:hamid.ragab@adfca.ae

Food Preservation:

 Since his being on earth million years ago, man practiced food preservation to fulfill his needs during the times of scarcity and droughts .The process of grain storage in mentioned in the Holy Quran in Surat Yusuf “((Joseph) said: For seven years shall ye diligently sow as is your wont: and the harvests that ye reap, ye shall leave them in the ear,- except a little, of which ye shall eat.(47) Then will come after that (period) seven dreadful (years), which will devour what ye shall have laid by in advance for them,- (all) except a little which ye shall have (specially) (48). Drying and burying were among the most important methods of food preservation.
Sciences related to food preservation were developed with the continuous need for long-time storage of food. Food preservation is defined as the process of addressing and dealing with food in a way that maintains its taste and preserves its nutritive value as long as possible via stopping or slowing spoilage with the aim of preventing foodborne Illnesses. The process of food preservation include inhibiting the growth of bacteria, fungi and other microorganisms besides slowing down the process of oxidation of fats, which causes food Rancidity.
The most common food preservation methods include drying , freezing , vacuum-packing, canning , Preserving in syrup, sugar crystallization, salting, irradiation, the addition of  preservatives and inert gases
.

Freezing:

Freezing is the most common method of preservation. Beside minimizing the spoilage of the food, the crystals resulting from freezing of the water content of the food prohibits the growth of more than 99% of the spoilage bacteria and retards most of the enzymatic reactions that take place in food.

The shelf life of the frozen food can be more than 12 month if frozen and stored in -18 °C (0 Fahrenheit) .

 

 

Thawing:

Upon removal of frozen food items from the freezer bacteria start multiplying within the dangerous zone (40 – 140 °F( therefore the defrosting process should be looked at as a race between the consumer and the bacteria with the aim of completing the defrosting process in way that maintains the taste and nutritive value of the food before the bacteria exceeds the permitted concentrations. Bacteria win this race if food is kept more than 2 hours within the dangerous zone.

Thawing Methods:

The most common thawing methods of frozen food include:

  1. Refrigerator Method
  2. Cold Water Method.
  3. Method Microwave.
  4. Cook it frozen method.
  5. Metal pan method
  6. Room temperature method
  7. Warm water method

  

1. Refrigerator Method:

The packed frozen food is placed in a refrigerator (4-6 C) .The drippings are collected in a pan.

This method reserves energy as the frozen food help cooling the refrigerator. Food thawed using this method can be directly cooked and in some instances they can be refrozen if not consumed.

All frozen food can be thawed with this method, however it is the ideal method for frozen fruits, frozen meat and fish and their products .The slow thawing helps the meat fibers absorbing the fluids resulting from the thawed ice crystals and this increases the tenderness of the meat. Within a refrigerator, a kilo of meat can be completely thawed within 12 hours whereas a kilo of fish or fruits needs 12-16 hours for complete thawing.

 

 

  2. Cold Water Method:

The frozen food is wrapped in a plastic bag and placed in cold water however water should be changed every half an hour to maintain it cold .Exposing the frozen food to running tap water is a quicker and safer way to defrost frozen food. Food thawed via this method should be immediately cooked.

Practically defrosted food might be left if water for more than 2 hours with the possibility of the water heats up therefore food controlling authorities world wide do not recommend this method for restaurants, some of the authorities prohibit it.

This method can be used for defrosting meat and meat products (hamburger, nuggets …etc). A kilo of meat needs 2 hours for complete thawing whereas fish should not be thawed completely using this method and a kilo of fish needs more than 3 hours to be ready for cooking. Cooked shrimps and leafy vegetables (such as mallow) and fruit can be thawed using this method.

 

  3. Method Microwave :

The unwrapped frozen food is placed in a container suitable for microwaving. The microwave is operated in the defrosting mode where only 30% of the energy is used. A 2 inch distance between the food and the inner walls of the microwave should be left. Small food items (e.g. nuggets) should be dispatched before being placed in the microwave.

This method is ideal for crean cheese, cheesecake and small size cooked meat and food. Large parts of meat and fish are not adviced to be thawed using the microwave as the outer surface might get cooked while the inner part is still frozen. A piece of cheesecake needs 15 seconds to be completely thwaed.

   

4. Cook it frozen method:

The frozen food is unwrapped and cooked while frozen. It should be cooked for a relatively longer time than fresh and or thawed food.

This method is ideal for frozen vegetables, ready-to eat frozen food, small cuts of meat, chicken and fish. Large cuts of meat ,fish and chicken should not be cooked while frozen.

 

 .5 Metal pan method:

The frozen food is placed in a stainless steel container and kept to thaw in room temperature (25 °C). The food shouldn’t be left for more than 2 hours. Do not use this method to thaw meat and chicken.

 

6. Room temperature method:

The frozen food is left on the table to thaw at room temperature. As air movement accelerates the thawing process, it is recommended to expose the food to flow of air via a table fan.

This method is ideal for frozen bread and cakeries.

 

7. Warm water method

Frozen canned juices are placed under running or immersed in warm water.

 

8. Other thawing methods :

Other uncommon thawing methods include Antifreeze protein High-pressure thawing، Ohmic thawing

 

Thawing frozen breast milk :

                                                                                                                                                             

To thaw frozen breast milk it is advisable to place the container in a refrigerator overnight. A quick method of thawing breast milk is by placing it under running warm water

  

References

 

1.   Standardization Organization for G.C.C.(GSO) ,Standard number UAE.S/GSO 150/2007 :Expiration Periods of food products

 2.    Australian Dietary Guidelines for Children and Adolescents - Commonwealth of Australia

 3.   Fellows, P. In: Food processing technology – principles and practice (2nd ed.), Ellis Horwood, Chichester, UK (2000), pp. 369–380.

 4.   Fu, W.R. and Hsieh ,C.C. (1999). Simulation and verification of two-dimensional ohmic heating in static system. Journal of Food Science 64 (6): 946–949.

 5.   Li, B. and Da-Wen Sun (2002). Novel methods for rapid freezing and thawing of foods – a review. Journal of Food Engineering  54(3):175-182

6.   Li,J. and Lee, T.C. (1998). Bacterial extracellular ice nucleator effects on freezing of foods. Journal of Food Science, 63 (3): 375–381

7.   Manual on meat cold store operation and management (1991).FAO corporate document repository.

8.   Ohtsuki, T. (1993). Process for thawing foodstuffs. European Patent 0409430

 9.   Sigurgisladottir,S. ; Ingvarsdottir,H. ; Torrissen,O.J. ; Cardinal,M and Hafsteinsson ,H.(2000). Effects of freezing/thawing on the microstructure and the texture of smoked Atlantic salmon (Salmo salar). Food Research International, 33 : 857-865.

 10.        Zhao,Y.Y.; Fores, R.A. and Olson ,D.G.(1998). High hydrostatic pressure effects on rapid thawing of frozen beef. Journal of Food Science, 63 (2) : 272–275.