What methods of freezing fish exist, and what are their features?
Long-term storage of products of natural origin is often complicated by the activity of microorganisms and bacteria that infect the meat of the creature and render it unusable.
The same applies to fish that is caught far from the coast and populated areas.
It may take several weeks for high-quality and tasty seafood to reach the table, which is not possible under normal conditions. The solution to this problem is to properly freeze the fish.
We will talk about popular methods of freezing fish below.
Content
Why do you need freezing?
Freezing is considered one of the most effective methods of preserving food.
Done correctly the procedure allows you to preserve nutritional and taste characteristics fish for an extended period.
Freezing is also used as a preparatory measure prior to removing moisture from the product using mechanical or thermal methods.
Kinds
Let's look at existing methods of freezing different types of fish.
Marine
It is not uncommon for a fishing vessel to be away from the shore for a long period of time. Often there is a need to preserve the marketable appearance of fish caught in the early days. In such circumstances, sea freezing is used, which is carried out directly on the ship.
To preserve seafood, you will need to install powerful freezers on the ship. The speed of freezing allows you to fully preserve the texture of meat, its taste and nutritional properties.
Coastal
In this case, the procedure is implemented in the factory. Therefore, fishermen will need to deliver seafood to the port, after which the catch is transported to the plant.
Methods
What are the ways to freeze fish?
Natural
Natural freezing is considered obsolete with almost no practical value. And yet, in rare cases, this method is used in certain areas where stable frosts persist for a long time.
The essence of the natural method is a simple sequence of actions:
- An open area is usually selected and cleared directly next to the fishing site.
- The snow in this area is filled with water to create a smooth ice surface.
- After catching, the fish is immediately placed on the platform in one layer and left for several hours to completely freeze.
At ambient temperatures down to -15 degrees, seafood quickly freezes, while maintaining its presentation and taste.
What are the signs of natural freezing in fish? Fish frozen naturally at temperatures below -10 degrees, has the following characteristics:
- fins - spread out;
- eyes – bulging;
- a crust of ice on the surface;
- There are slight streaks of blood located near the space between the gills.
Artificial
Artificial freezing of seafood is carried out in special chambers and structures using refrigerant, in which the temperature is set to no more than -23 degrees. The fish is placed in an even layer on special shelves made of galvanized iron.
Freezers can accommodate large quantities of seafood, but The freezing process itself is quite slow - it may take up to 5 days. At the same time, the quality is negatively affected by sharp temperature changes that arise due to the need to load a new batch and remove the finished one.
There are many varieties of freezing structures for artificial freezing in which fish can be placed: suspended on hooks, on cargo trolleys, etc.
Intense air
To increase the efficiency of artificial freezing, special installations are used.
They use cold air as a coolant, circulating at a speed of 5-7 meters per second.. These devices are installed on most fishing vessels.
The product is placed on metal trays with lids that are placed between two surfaces where the refrigerant circulates. Using this method, more than 90% of seafood is frozen in the Russian Federation.
Product processing with tile chambers
Such chambers are freezers with flat horizontal/vertical tiles through which refrigerant circulates.
The operating principle of the devices is based on the most intense heat exchange when the fish comes into contact with the cooling surface. Such cameras are quite compact and effective. – in 3-4 hours they can freeze up to 1,200 kilograms of catch.
Cold brines
When brine freezing, special solutions of table salt are used, the concentration of which varies between 18-22%, and the temperature - from -16 to -20 degrees.
Boiling refrigerants
The principle of using boiling refrigerants for freezing based on spraying liquid nitrogen in special installations. Bringing the product to the desired state occurs quickly, the quality is very high, but the cost of this method is excessive, so it is used in exceptional cases.
Shock
The essence of blast freezing is not so much the use of lower temperatures, but rather a significant increase in the cooling rate.
The principle is:
The fish is cooled in chambers with a gradual temperature change from +20 to 0 degrees.- The initial stage of freezing is performed. Within 20 minutes the temperature changes from 0 to -5. Standard freezing at this stage takes 100 minutes.
- Freezing occurs - the temperature drops to -18 degrees.
- The final stage is shock freezing. The temperature drops to -30 degrees within 40 minutes. With standard technology, you will have to wait 2.5 hours, while the minimum temperature is -24 degrees.
During shock freezing, the crystallization of product fractions is less intense, which has a positive effect on its quality.
Glazing
The essence of glazing seafood is to form an ice shell no more than 4 millimeters thick on the surface.
Thus:
- the catch is protected from the influence of negative environmental factors;
- oxidation of the fat layer is prevented;
- Drying of the fish is avoided.
The glaze is formed by placing seafood in fresh water with a temperature of 1-2 degrees.
How to properly freeze fresh food at home?
To achieve the greatest efficiency in freezing fish at home, you need to proceed as follows:
- Gut and clean the fish. At the same time, it is important not to lower the water, because during subsequent defrosting the product will fall apart. To clean, the surface can be wiped with a damp cloth.
- Grease with vegetable oil.
- Wrap each fish in cling film or foil.
- Place in the freezer.
If the fish is too large, you can cut it into pieces.
Video on the topic of the article
This video will tell you how to freeze fish:
Conclusion
So, properly performed freezing allows you to preserve the taste and quality characteristics of the fish. There are many different methods in this area.
However, the most used methods are:
- standard artificial freezing,
- intense air,
- using tile chambers and shock.
The natural method has lost its effectiveness, the use of boiling refrigerants is not economically feasible, and cold brines salt the fish.
