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Where did the fish odour go?

Farmed cod contains far less of the substance that develops into fish odour than wild cod, a new Doctoral degree shows. In Norway, the amount of this substance is used to determine how fresh the fish is.

Wild cod is known to have a high content of trimethylamine oxide, which transforms to fish odour (trimethylamine) during storage.

Studies show that farmed cod has a significantly lower content, which can probably be attributed to the food it eats.

"Consequently, this cannot be used as a quality goal for farmed cod in the same manner as it is used for wild cod," says Scientist Hilde Herland at Nofima Marin, who presented her doctoral dissertation on December 11, 2009, at the University of Tromsø.

Quality

Limited information is available about the quality of products from farmed cod. Hilde Herland wanted to study what happens with fillet quality when the fish is stored in ice, and whether there are differences between farmed and wild cod.

The result shows that bacteria growth is significantly lower in the fillet of farmed cod. The number of specific undesirable bacteria was also lower and was often not established.

“This indicates that fresh products of farmed cod can have a longer shelf life than wild cod, and this is something that should be studied further,” says Herland.

Seasonal variations

The quality of farmed cod also has seasonal variations, as is the case with wild cod. The quality was reduced in late spring and during summer.

It is common to add minerals and trace metals in cod feeds. This study shows that this impacts on neither growth nor quality. However, salted fish from farmed cod had a yellow miscolouring, which reduced the quality.

Herland, who has worked as a scientist at Nofima Marin since 1999, works with analytical methods and fillet quality of farmed cod. She has a Master of Science from the Norwegian Institute of Technology.

Farmed cod contains far less of the substance that develops into fish odour than wild cod, a new Doctoral degree shows. Photo: Frank Gregersen
Copyright: Nofima

Farmed cod contains far less of the substance that develops into fish odour than wild cod, a new Doctoral degree shows.