Thomas Larsson developed a PhD project stressing new gene technology methods. (Photo: Nofima)

Salmon fillets can be made firmer

NORWAY
Monday, November 19, 2012, 22:30 (GMT + 9)

The firmness of salmon fillets is something the consumer perceives as a characteristic of quality and is an important factor for processing to be considered by the producer. By making use of new gene technology methods in quality research, in his PhD project Thomas Larsson points to the fact that the key to a firmer fillet lies in efficient metabolism of nutrients in the cells, and that this is determined by the genes in the fish.

“In order to find the biological difference in salmon with soft and firm fillet, we have used a method called microarray. This is a method used to study if genes are turned on or off in salmon with varying firmness in their musculature,” says Larsson.

“Gene analyses tells us what happens in the fish at a molecular level and indicates the cause of undesirable softness in farmed salmon fillets. By studying thousands of genes simultaneously, the method functions as an efficient screening tool to point to key factors that influence the firmness.”

The microarray used here is specific for salmon and was developed at Nofima Mat, the Norwegian Institute of Food, Fisheries and Aquaculture Research, by Aleksei Krasnov. This is a suitable method for studying regulation of genes in salmon.

This new approach regarding the use of method in Larsson’s work made it possible for the first time to map the biological causes of variation in the firmness of salmon fillet.

Efficient conversion of nutrients occurs in the cellular energy plants, the mitochondria (aerobic metabolism). The gene analyses showed that salmon with firm fillet had more aerobic metabolism, by using fat as fuel, than salmon with softer fillets. Efficient mitochondria were a requirement for the formation of firmer salmon fillets.

The knowledge from the gene analyses was used as a basis to design salmon feed that stimulates formation of firmer fillets. A feeding trial involved salmon feed with extra amino acid supplements (glutamate) being fed to one group of salmon, while another group received normal feed.

The salmon that received the feed containing extra glutamate had stimulated aerobic metabolism, which resulted in a firmer fillet.
 
Positive health benefits were also observed. Sick salmon are not in a position to fulfil the biological requirements to form normal firm muscle, and these fish instead developed abnormally hard muscle.

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