In freezing with brine, the fish is frozen by contact with a refrigerated liquid suitable for contact with the fish. Various types of brine are used but those with sodium chloride are most important and most economical for fish.
The freezing temperatures are then limited to -18 °C (NACl) to around – 25 °C due to their eutectic points, and the fish is frozen by spray freezing or by immersion in the brine.
In tuna fisheries, such brine has been used for quick freezing of fish on board directly in the wells.
Spray brine has been used in smaller vessels on order to decreases the weight of brine on board. A small tank of brine can be kept as a reservoir for the spray, thus eliminating the full flooded holds.
Freezing by sprinkling is used for freezing herring and mackerel in Scandinavia particularly Norway. The boxes of fish are placed in stacks.
On top there is a box with a perforated base in order to distribute the brine evenly. The brine passes from one box to other and down into a tank where it again passes over cooling coil and is then pumped up and sprinkled over the boxes of fish until the fish is frozen (1-2 hours).
Using modern blast freezers operating at temperatures as low as -50 to -60 C, the fish may be frozen less than 24 hr.
Brine freezing, once popular in the tuna fishing industry, is begin replaced by air-blast freezers for preservation of the catch.
Brine freezing of fish
