Photo credit: Chalmers University of Technology

When filleting pelagic fish, the common practice is to collect all off-cuts such as heads, tails and backbones in one bin. This immediately reduces the quality of the off-cuts as they become contaminated with e.g. blood, enzymes and residues from the intestines. Consequently, the use and value become limited, which is why the off-cuts typically are sold for feed production.

However, if handled correctly, there is great potential for using the off-cuts for more valuable purposes such as high-quality food ingredients for fish burgers as they are rich in proteins.

This requires a change in the existing logistics – a challenge, which the partners in the EU-funded project WaSeaBi have taken up by developing a new sorting technology that makes it possible to separate herring into head, backbones, viscera + belly flap, tail in addition to the fillet.

Successful implementation of sorting technology
The sorting technology has successfully been implemented at the herring processing company Sweden Pelagic AB in close cooperation with Chalmers University of Technology. And these new fractions can form the basis for development of new products at Sweden Pelagic.

“The sorting technology gives us a lot more possibilities to develop new healthy and tasty seafood. In the long run, we hope it will give us a better revenue,” says Martin Kuhlin, CEO of Sweden Pelagic AB, one of the industry partners. “I think that it will give us great advantages in the future. The technology will make it possible to extend our product range. This year, we estimate that we will produce around 200 – 300 tons of ‘herring mince’, and the ambition is to increase that number every year.”

In addition to the possibility of developing new products, increasing the revenue and extending the product range, Martin Kuhlin also thinks that via the sorting technology they will be able to market their products towards new consumer groups.

“In the first case, we will sell the products to the industrial customers, who manufacture pan-ready or eat-ready products. But we have experienced that also school kitchens and “public meal producers” have a great interest in the mince.”

From 1 to 5 different cuts of the fish
The new sorting technology has been developed by re-building a filleting line for pelagic fish, which now fractionates and separates the fish into 5 different clean parts. This means that Sweden Pelagic AB now has 5 cuts instead of one, which they can sell for subsequent production of food raw materials and ingredients such as minces, protein isolates, hydrolysates and oils.

And the sorting technology can also be applied to other fish species, however, Martin Kuhlin points to a challenge in the fish industry: “I really believe that we, in the fish industry, are way behind for example the meat industry. They have for a long time been very good at taking care of the whole animal in a much better way than ‘our’ industry.”

Ingrid Undeland, Professor of Food Science at the Department of Biology and Biological Engineering at Chalmers University of Technology, who has been working on the technology adds that “It is of course important that the off-cuts are handled just as carefully as the main product i.e. the fillet, where focus is on preserving the quality throughout the whole value chain. Thus, instead of seeing the off-cuts as side-streams or by-products, which indicates that they are “leftovers”, they should be seen as just another cut of the fish - just like in the meat industry.”

In the study, Lipid oxidation in sorted herring (Clupea harengus) filleting co-products from two seasons and its relationship to composition, which was published with open access in Food Chemistry, you can read about the five sorted herring fractions’ susceptibility to lipid oxidation during ice storage. One of the conclusions from the study is that sorting herring filleting co-products to reach a broadened food production from this species, going beyond just the classic fillet, is advantageous to avoid that the most pro-oxidant-rich parts “contaminate” the more stable ones.