Best quality achieved when cod are salted after rigor
The results from Nofima’s research are unequivocal: live-stored cod for salted fish should not be salted until rigor has passed.
Scientific researchers engaged in the Catch project looked at the use of live-stored cod for conventional products such as stockfish, salted fish and dried/salted fish. The objective was to develop production of traditional high value products intended for a premium market.
The researchers concluded that live-stored cod does not necessarily provide any benefits in terms of quality when it comes to the traditional products. However, if live-stored cod is to be used for salted fish or dried/salted fish, it should be stored on ice and processed after rigor is over.
Filleting and salting should generally be performed once rigor is over. The results indicate that this contributes to higher product yields and lighter colour.
Nergård as research partner
A total of eight companies have participated as research partners in the four-year project. Nergård was an active partner when live-stored cod were slaughtered in Senjahopen in the spring of 2016. Slaughter of live-stored cod, enabling pre-rigor processing. I.e. the fish can be filleted and salted before they go into rigor.
To preclude possible quality differences due to rigor status, the cod was filleted in pre-rigor, in rigor and in post-rigor conditions. After filleting, the fillets were salted and left for six weeks, after which half were dried into salted dried fish (clipfish).
The other half were kept in salt for another six months, until they were dried into salted dried fish. The effect of salting on yields, smell and colour were recorded during the project, based on different times for filleting (pre-rigor, in rigor and post-rigor). Post-rigor fillets of line-caught cod were used as control.
10 percent lower yield
The biggest difference in terms of yield and colour of the fillet, was the time of filleting. The researchers found distinct differences between pre-rigor and post-rigor produced fillets. Salting in the pre-rigor stage gave up to 10 percent lower yield. Pre-rigor salted and salted/dried fish fillets were also found to be significantly yellower in colour. The results also show that salting and drying can hide severe quality faults like blood spots and yellow discoloration. The quality faults appeared on surface again after desalting and re-hydrating the filets.
Line-caught cod that was filleted and salted post-rigor showed no difference in terms of yield and quality compared to live-stored cod filleted and salted post-rigor. The researchers concluded that live-stored cod does not necessarily provide any benefits in terms of quality compared to traditional products.
“In general, the fish should be stored on ice and salted once the rigor process is over. The results indicate that this contributes to higher product yields and lighter colour,” says researcher Stein Harris Olsen.
Good quality for stockfish
Other results were found for the production of stockfish. Live-stored cod can be cut and hung before the rigor occurs. Stockfish produced using this method achieve very good quality. The surface on the muscle side can be uneven, but there is little cleavage and few faults on these stockfish.