Freezing Fish
freezing technique | thawing technique | refreezing | storage life
Freezing is the method most people choose for preserving fresh fish and other seafood products. However, this preservation technique is effective only if the product is handled in such a way that its quality is kept near peak freshness. The quality of frozen seafood is directly related to the quality of the starting material. If the seafood you freeze is of poor quality, the seafood you thaw will be of poor quality--perhaps even poorer.
Proper Freezing Technique
It is best to freeze fish and seafood products rapidly. Turn your freezer down to its lowest (coldest) temperature setting, and don't overload it by trying to freeze too much at one time. If you usually keep the freezer temperature higher than its lowest setting, be sure the seafood is completely frozen before turning the temperature back up to its usual setting.
If seafood is frozen slowly, large ice crystals may develop inside the flesh tissues, which can cause physical damage to the tissue cell structure. Ruptured tissue cells means increased drip-loss during thawing. The moisture loss from thaw-dripping and the associated loss of water-soluble parts of the damaged tissue will, in turn, affect both the texture and flavor of the cooked product.
Proper Thawing Technique
Proper thawing is just as important as proper freezing. Cold running water remains the fastest and best means of thawing seafoods. If the product is not already in one, put it into a waterproof plastic bag, force out all the air you can, and seal the bag. (It is necessary to expell the air from the bag because air is a good insulator and will extend the thawing time.) Place the bag into a pan, kettle, or sink and run cold water into the container and over the plastic bag. With thin packages, such as individual fillets, the thawing process should take no longer than 5 to 10 minutes. Thicker packages will take longer.
Seafoods can also be taken directly from the freezer and cooked. However, if you use this procedure, remember that it will take longer to cook the seafood.
Another acceptable method for rapidly thawing seafood is to use a microwave oven. Slow thawing (overnight) in a refrigerator) is an acceptable practice, but excessive drip-loss can occur when this procedure is used. As noted earlier, a large amount of drip-loss can result in a drier and less succulent product.
Thawing seafood products at room temperature should never be attempted. Thawing at room temperature is a slow process, and warming the outer product surface can allow bacterial growth and spoilage to occur while the inner flesh is still thawing. Thawing seafoods in hot water is also not recommended. Hot water thawing can both denature tissue proteins and initiate cooking. The end result is a loss of tissue moisture, textural changes, and flavor loss.
Refreezing Fish
Is it safe to refreeze fish that has been previously frozen and then thawed?
If the fish has been thawed and handled properly (in the refrigerator, not at room temperature), refreezing will not introduce any new food safety risks. (See the above section for proper thawing technique.) However, the process of thawing and refreezing can cause toughening, loss of flavor, and other food-quality problems.
Storage Life
Frozen fish of good quality that were handled and frozen properly from catch to the freezer should remain of high quality for the period listed on page 2. These time periods are approximate and assume a freezer temperature of 0 degrees.
For a free printed copy of the complete brochure, "Home Freezing of Fish," by David A. Stuiber, email your mailing address to linda@seagrant.wisc.edu
copyright 2001 University of Wisconsin Sea Grant Institute
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