Scientist and author, Beth is also a keen home cook. She enjoys trying new recipes.
3 Main Ways to Preserve Fish
Like any natural resource, the supply of fish can vary from glut to scarcity. To avoid starvation, humans have learned to preserve fresh fish so that it stays edible for long periods of time. This is particularly important in communities that have no other source of protein.
The key to success is to stop the process of decomposition and bacterial growth. To survive and grow bacteria need (i) moisture, (ii) warmth, (iii) oxygen, and (iv) time. Food preservation works by removing at least one of these four conditions. The most common methods of preserving fish are as follows.
- Salting and Sun-Drying: These methods involve dehydrating the fish.
- Freezing: This locks up the water as ice and so prevents bacterial growth.
- Vacuum Packing: This works by removing the oxygen.
If you want to save your own excess catch or harvest. I recommend A Guide to Canning, Freezing, Curing and Smoking Game and Fish. It's a well-written guide to the techniques of preserving food at home.
1. Salting and Sun-Drying Preserve Fish
The oldest methods to preserve fish are by salting or dehydrating the food. Salting fish dries the flesh because it draws out moisture, and so prevents bacterial growth. Drying outdoors under the sun is possible in some places. In cooler climates, water is removed using dehydrator machines. This can be done at a domestic level as well as in large industrial sized dehydration plants. When done properly, both sun-dried and salted fish can remain edible for many months. Before cooking, the fish is rehydrated by soaking overnight in potable water.
Table salt or sodium chloride is one of the most common chemicals used in food preservation. Virtually all cultures from ancient times to the present day have used mineral or sea salt to preserve food.
The main principle behind this method is desiccation through osmotic pressure, where the water inside the cells of food is absorbed by the salt. Most bacteria cannot grow in an environment with high salt concentration. Like every other living organism, bacteria need water to survive.
2. How to Preserve Fish by Freezing
Freezing preserves fresh fish by locking any water present into a solid form (i.e. ice). This makes the water unavailable to bacteria and thus prevent bacterial growth. Unfortunately one of the side-effects of freezing fish can be that frozen water crystals pierce the cell walls. This can make the defrosted fish mushy in texture. To limit this type of cell damage fish should be frozen using a process known as quick freeze-drying.
Freezer burn can also be a problem if the processed fish is not protected once frozen. If left for too long in a freezer, the intense cold can cause further drying and damage to the surface of the flesh resulting in a “burn”. This can be avoided by vacuum packing the fish before freezing it. Alternatively the fish can be packed in a sauce so that the drying effect of freezing acts on the sauce rather than on the fish itself. The video below demonstrates how to freeze fish effectively and how to avoid it being affected by freezer burn.
How to Freeze Fish and Avoid Freezer Burn
Benefits of Freezing Versus Salting or Drying Methods
Frozen fish tends to be more popular with consumers than salted and dried fish because freezing does not affect its flavor. Frozen fish can be cooked straight from the freezer with little loss of quality compared to the fresh product. Salted and dried fish on the other hand, needs to be soaked overnight in water to allow the flesh to rehydrate. Even if the soak water is changed several times, the fish still retains a salty taste that isn't found in fresh fish.
Manufacturers recommend you eat their frozen fish within three months of purchase, but you could leave it in the freezer for up to six months with no ill effects. Salting or drying the fish can make it last up to twelve months providing it is kept in cool dry conditions. If you combine the two methods i.e. freezing an already salted or dried fish, there is little to be gained. The taste of the fish has already been changed by the dehydration process. Placing it into the freezer will not regain that fresh fish taste.
Don't Freeze Fish That's Already Dried or Salted
Researchers in Reykjavik, Iceland carried out controlled experiments to measure the effect of freezing on already dehydrated cod fish. They looked at changes in physical weight of fish stored for up to six weeks at a variety of cold storage temperatures.
The 2007 study looked at the effects of storing and drying on the quality of cured salted cod. The research conclusions were clear. At the lowest temperatures i.e. at -18 C and -24° C water content of the fish was greatly reduced and as a result, the fish lost weight over the six weeks of the experiment. There is therefore not only no need to freeze fish that has already been dried or salted, but freezing such fish is likely to result in deterioration in eating quality.
How to Vacuum Pack Fresh Seafood
3. Reduced Oxygen Method or Vacuum Packing
Freezing, drying and salting are not the only ways that fish can be preserved for later eating. Vacuum packing of fish is often carried out in conjunction with one of these methods, but it can be done on its own. Vacuum packing is simple to do at home with the correct equipment. A vacuum sealer machine sucks all the air (oxygen) out of the vacuum bag and then heat seals it. It's easy to use and small enough for domestic use. Once bagged, the fish will stay fresh for up to a year in your freezer. Freezing a bumper catch after having vacuum packed it first will increase its freezer storage life from six months (without vacuum packing) to one year (with vacuum packing).
How Many Methods of Preserving Fish Are There?
The following list is not exhaustive. It contains the most common methods of preserving fish.
- Dry salting.
- Brining (wet salting.)
- Hot smoking.
- Cold smoking.
What Percent of a Whole Codfish Can Be Eaten?
The amount of edible flesh (or fillets) on a fish sold in retail stores is only about 50% of its original weight. There is also a small amount of meat on the head, including the cod cheeks. The tongue, the swim bladder (sounds) and the skin are eaten in Nordic and Slavic cultures. Smoked cod's roe is a particular delicacy. Cod liver oil is used around the world for medicinal purposes. The skin and bones of the fish can be used to make soup, so nothing need be wasted.
The video below shows a whole cod being eviscerated and filleted to get the maximum yield from a fish. It includes some tips on the best ways to salt and dry your catch.
How to Fillet a Codfish Demo
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.