Fish sold chilled is called ‘fresh’ fish, and the consumer assumes that it is of better quality than fish sold frozen, regardless of the time the fish was caught and the treatment it may have received before being offered for sale.
While fish may be processed, frozen and packed onboard a factory trawler within a few hours of being caught, fish sold chilled or ‘fresh’ will have been held in the hold of a catching vessel for some time before spending even more time in a land-based distribution chain before it reaches the retailer.
Therefore it is essential, when processing fish onboard for selling it as fresh, to cool the fish down as soon as the net is emptied, and to keep it cold while processing it as quickly and efficiently as possible.
3X Technology of Iceland has developed an onboard processing system for fresh fish that the company believes meets those objectives. A key component of this system is the use of a screw tank for bleeding and chilling fish on the processing deck that the company introduced at this year’s Seafood Processing Europe.
The use of this equipment ensures all fish receive equal time through the bleeding and chilling process. "By using screw tanks it is guaranteed that the first fish that enters will be the first fish out," the company says. All the fish will receive a uniform bleeding and chilling time which is probably not the case with vessels’ existing systems.
Some fish may pass through a chilling system too quickly, whereas other fish may stay there for an extended period. On some vessels there may be no chilling on the processing deck at all; fish will only be chilled when it reaches the hold. "If the fish has not been given a proper bleeding time before being immersed in liquid ice in the holding room, then the bleeding process stops and that leads to discoloration (darker colour)", says 3X.
According to the company, the major factor affecting shelf-life and therefore the quality of fish is the time taken for rigor mortis to set in, and the length of time taken for the fish to go through rigor. The timing of rigor mortis also affects the amount of flaking and the processing yield, it adds.
"Fish does not start to lose its freshness until the rigor mortis process has ended. A fast rigor process leads to higher level of flaking, less yield and shorter shelf-life. Therefore it is of the outmost importance to delay the start of the rigor process and equally important to have that process as long as possible."
3X Technology uses slurry ice in its screw tank and therefore starts to bring down the temperature of the fish as soon as it has been sorted (into species), cut and gutted.
The new tanks can be used on vessels 60-200 feet long, according to 3X, which adds that its onboard gutting and trimming lines are designed to endure a great deal of strain and work for long hours.
