New Technique Allows Longer Shelf-Life

The Fish Site
by The Fish Site
23 November 2006, at 12:00am

NORWAY - It will now be possible to extend the shelf life of fresh fish fillets.

This is a superchilled cod fillet, ready for export. Because some of the water freezes during superchilling, it will be harder and stiffer than a fillet chilled the regular way.

Exports of fresh fish will thus become easier for the Norwegian seafood industry, which has a long way to the markets in Europe. The method is called superchilling and involves chilling the fish fillet down to between minus 1-2 degrees Celsius.

Despite the below-freezing temperature, the special properties of the fish muscles mean that only a small part of the water in the fillet freezes at this temperature.

Thus, the muscle cells won't burst due to ice formation, as in normal freezing, and the fillet retains the properties that characterise the quality of a fresh fillet.

One to two days

"Our test shows that the shelf life was extended by 1-2 days when the fillet had been superchilled", says Senior Scientist Leif Akse at Fiskeriforskning.

In the test, cod was filleted, superchilled and packed at Aker Seafood's plant in Hammerfest, and then transported to the company Thorfisk in Denmark. The superchilled fish, which was sent in crates without ice, was compared with fillets that were chilled with regular ice during transport.

Scientist Torbjørn Tobiassen preparing the transport of superchilled cod fillet to Denmark.
At Thorfisk's plant, the fillets were cut into smaller pieces and packed in so-called modified atmosphere, the same procedure the company uses with its regular tray-packed cod fillet products.

Modified atmosphere involves replacing the oxygen by other types of gas to inhibit the growth of bacteria and thereby extend the shelf life. In this case, the products were additionally stored at 2 degrees above zero until the expiration of the shelf life, and the quality was checked along the way.

Saves money and the environment

The extended shelf life which superchilling renders possible can be important for the Norwegian seafood industry because it takes a long time to transport the fish to the markets in Europe.

Superchilling also saves freight costs because no ice is used in the crates. Instead of packing 5 kg of fish and 1 kg of ice, 6 kg of fish can be put in the crate. A lower transport volume is also environmentally friendly because fewer lorries are needed to transport the fish.

Industry and research

The project is a collaboration amongst the Fillet Forum in the Norwegian Seafood Federation, Aker Seafood Finnmark, Thorfisk, SINTEF Energy Research and Fiskeriforskning. The project is financed by the Fishery and Aquaculture Industry Research Fund. Fiskeriforskning's report no. 23/06 (only in Norwegian) describes the project and can be downloaded here.

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