Nofima has found that fish which is bled, cooled and stored correctly can keep for at least 24 hours before being gutted and still maintain good quality.
Nofima has, on commission from RUBIN, studied the significance for quality of the time between catch and gutting, and the optimal storage method for ungutted fish.
The scientists tested various methods used to handle cod, haddock and saithe after the fish are taken on board the boat and before they are delivered to the fish processing industry.
“In order to be best suited for being stored ungutted, the fish must be bled in water as soon as it comes on board the boat and before it is transferred to cooling in storage tubs” says Nofima Senior Scientist, Leif Akse.
The meat of fish that is left to bleed in cooling containers with ice slurry or chilled sea water (CSW) can become discoloured. The recommendation from the scientists is that cooling must begin as soon as the fish is properly bled.
Having good cooling onboard and on land is decisive for how long the fish can be stored ungutted. The fish is normally stored in ice slurry, CSW or refrigerated sea water (RSW). The research results point to the fact that all these cooling methods may be used to store ungutted fish, but it varies how long the fish can be stored before the quality is reduced.
“Cod which is cooled in ice slurry at a temperature of -1.25 °C can be stored ungutted for up to 24 hours without reducing the quality of the fish or by-products. At higher temperatures (0 °C), the fish can be stored for around 20 hours,” says Mr Akse.
Haddock proved to be less suited to storage ungutted than cod, and showed more signs of discolouration and smell. However, with good cooling in ice slurry onboard and on land, haddock can nonetheless be stored for 24 hours without any unacceptable reduction of quality.
The scientists are of the opinion that bled and well cooled saithe caught with gear that causes a low degree of catch damage, such as longline or seine, can probably be stored equally as long ungutted as haddock or cod without an unacceptable reduction of quality.
However, fish to be stored ungutted should not have any stomach content. Net-caught saithe with high stomach content was damaged by belly bursting 24 hours after being caught.
