How to freeze fish such as tuna, salmon and cod, including defrosting instructions.

freeze fish
Nowadays we are able to purchase fresh fish already frozen from our local supermarket or freshly caught fish from our nearby fishmonger or indoor food market. If you have caught your own fish or would like to freeze a quantity of freshly caught local fish, read the following article for some ideas and useful information on how to freeze fish at home.

The first and most important rule when freezing fish is that the fish must be as fresh as possible upon freezing. Ideally, fresh fish should be frozen within 12 hours of being caught and sooner if possible. The quicker the fish is frozen, the better quality is maintained and the longer the shelf life of the product.
Fresh fish is highly susceptible to food spoilage, bacteria and decomposition. Fish actually starts to deteriorate and lose quality as soon as it leaves the water. This is even more apparent during the summer in high temperatures.

Fish must never be left at room temperature for the above reasons and it is important to keep it cool and clean it as soon as possible after purchase or catching.

Secondly, fish must also be cleaned and prepared before actually storing it in the freezer, so this must also be taken into consideration when planning.

All types of fish can be frozen. Small fish such as sardines or whitebait should be frozen whole after cleaning, whilst larger fish may have the head and tail removed beforehand.

On the other hand, large flat fish such as cod, plaice or salmon may be divided into fillets and then frozen, or if you prefer some fish may be frozen whole by placing them on a bed of ice for aesthetic purposes.

All types of fish must be wrapped or packaged in airtight and moisture-vapour proof packaging such as aluminium foil, plastic containers, polythene bags or freezer-lock bags. Remove all air from the packaging as possible before sealing and over wrap with cling film if preferred. Ensure that all packages are labelled with the date, weight and contents.

There are several methods for freezing fish that involve using water. They are very effective and are detailed below.

Before freezing the fish, it must be washed, cleaned (scaled and gutted) and divided into portions if necessary. You can either clean and gut the fish yourself or ask your fishmonger to do it for you.

Lemon-gelatine method

  1. Mix 1¾ cups of water with ¼ cup of fresh lemon juice.
  2. Separate the liquid into quantities of ½ a cup and 1½ cups.
  3. Dissolve and mix one packet of plain gelatine into the ½ cup mixture of water and lemon juice.
  4. Heat the larger quantity of liquid in a saucepan until it is boiling.
  5. Stir in the gelatine mixture.
  6. Allow to cool to room temperature.
  7. Dip the prepared fish into the cool liquid and then drain.
  8. Wrap the fish in airtight packaging, squeezing out excess air. Seal and label.
  9. Freeze immediately.
If not using the above method to freeze the fish, you will need to treat the fish beforehand if using any of the following methods in order to achieve a high quality frozen fish. The way in which you treat the fish depends on the type of fish.

Fish can either be labelled as "lean" fish or "fat" fish due to the amount of fat that they contain.

Lean fish contain less than 4% fat and include cod, sea bass, haddock, snapper, hake, grouper, plaice, John Dory, whiting, sole, sea bream and most types of freshwater fish.

Fat fish contain over 4% fat. Although these types of fish contain more fat, studies have actually proven that eating fatty fish is more beneficial for one's health than eating lean fish. Fatty fish increase the levels of omega-3 fatty acids, which are good for the heart and help protect against heart and cardiovascular diseases.

Examples of "fat" fish include salmon, tuna, halibut, monkfish, mackerel, red mullet, herring, trout, eel and sardines.

Lean fish treatment

Lean fish should be dipped in a brine solution before freezing. Prepare the brine solution by mixing together ¼ cup of salt with 2 pints of water. Dip the fish in the solution for about ½ a minute and then drain. This will give the fish a firmer texture and prevent moisture loss on freezing.

Fat fish treatment

Fat fish on the other hand should be dipped for the same amount of time in a solution of ascorbic acid. This can be prepared by mixing 2 tbsp of ascorbic acid with 2 pints of cold water. This preparation is done in order to slow down deterioration due to rancidity, which would occur quicker in fatty fish due to the higher amount of fat contained in the flesh.

After treating the fish with one of the above preparations, you can continue to freeze the fish by one of the following methods.

Ice glaze

  1. Place the whole fish or smaller fish portions into a polythene bag and place in the freezer until frozen.
  2. Remove the fish from the freezer and from the plastic bag.
  3. Dip the fish for several seconds in a bowl full of ice-cold water.
  4. Return the fish to the bag and the freezer until the water hardens around the fish.
  5. Repeat the dipping and freezing process until a glaze forms around the fish, which is about ¼ inch (5mm) thick.
  6. Wrap the fish in freezer wrap or other airtight packaging and return to the freezer.

Ice block

  1. Place the fish in a shallow pan, container or dish.
  2. Place into the freezer and leave overnight.
  3. The following day, remove the solid frozen block from the container and wrap in moisture-vapour proof packaging. Label and return to the freezer.

Freezing times for fish

For the best quality fish, freeze lean fish for up to 6 months and fatty fish for between 2 - 3 months.

Defrosting frozen fish

Never defrost fish at room temperature. It can either be thawed in the refrigerator or under very cold running water.

Defrost fish overnight in the refrigerator and ideally it should be covered with a plastic bag or placed in a bowl, so that water does not drip onto other products inside the fridge.

If defrosting fish under a cold running tap, this could take up to an hour depending on the size of the fish. Never use hot water to defrost the fish as this could cause the fish to become contaminated with bacteria. If using this method, try to cook the fish as soon as it defrosts.

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