New dip solution turns whole fish into valuable food

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Chalmers University of Technology

When herring is filleted, more than half of its weight becomes an inferior “side stream” that never ends up on our plates – even though it’s high in protein and healthy omega-3s. Scientists at Chalmers University of Technology, Sweden, have now developed a special immersion solution with ingredients such as rosemary extract and citric acid that can significantly extend the shelf life of the side streams and increase the possibilities for use as food.

Techniques for upgrading these side streams to food products such as ground beef, protein isolates, hydrolyzates and oils are already available today and offer the possibility of reducing the current practice of using them for animal feed or, in the worst case, simply throwing them away.

The big challenge, however, is that the unsaturated fatty acids found in fish are very sensitive to oxidative degradation, so that the quality deteriorates after just a few hours. This leads to an unpleasant taste, smell, color and texture in the end product. Side stream parts of fish such as the backbone and head are so sensitive because they are rich in blood, which in turn contains the protein hemoglobin, which accelerates the breakdown of fatty acids.

“Our new technology offers the producer a valuable time window in which the side streams stay fresh longer and can be stored or transported before they are processed into various food ingredients,” says Ingrid Undeland, Professor of Food Science at the Department of Biology and Bioengineering at the TU Chalmers.

The new technology is based on a dipping solution with ingredients such as rosemary extract and citric acid. As part of a European project called WaSeaBi, Ingrid Undeland, together with colleagues Haizhou Wu and Mursalin Sajib, recently published a scientific study that examines the possibilities of the method.

Recycle the solution up to ten times

The results showed that immersing the sidestream portions from the herring filleting process in the solution prior to storage significantly increased the time to rancidity. At 20 ° C the storage time could be extended from less than half a day to more than three and a half days and at 0 degrees from less than one day to more than eleven days.

“And because the dipping solution covers the surface of the bypass parts with a thin layer of antioxidants, these are transferred to the next process stage and deliver more high-quality minced meat, protein or oil components,” explains Ingrid Undeland.

To make the technology cost-effective, the possibility of reusing the solution was also explored. The results showed that even after reusing the solution up to ten times, the rancidity was completely inhibited at 0 ° C. In addition, the solution was found to keep the fish hemoglobin in a more stable and less reactive form with the fatty acids, which the researchers believe explains the decrease in oxidation.

More about studying and the possibilities of side streams

The study Control Hemoglobin-mediated lipid oxidation in herring (Clupea harengus) co-products via incubation or dipping in a recycleable antioxidation solution was published freely accessible in the journal Food Control. It was based on herring sidestreams from Sweden Pelagic, however the results obtained from diving cod sidestreams from Royal Greenland also confirm that rosemary-based antioxidant blends offer good protection against oxidation. This means that the solution can be used to prevent various types of fish by-pass from going rancid. The study went online in February before its final publication in the July 2021 edition.

Examples of valuable by-streams of fish are, for example, the muscle-rich backbones and heads, which are suitable for minced fish or protein ingredients. Since the abdominal lobes and intestines are rich in omega-3 fatty acids, they can be used to make oil. The caudal fin has a lot of skin, bones and connective tissue and is therefore well suited for the production of marine collagen, for example, which is currently in great demand on the market. In addition to food, marine collagen is also used in cosmetics and nutraceuticals with proven beneficial effects on the health of our joints and skin.

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