When herring is cut into fillets, more than half of its weight becomes a low-value "by-product" that, although these scraps are equally rich in protein and healthy omega-3 fatty acids, never make their way onto our tables. Now, scientists at Chalmers University of Technology in Sweden have developed a special maceration solution whose ingredients include rosemary extract and citric acid can greatly extend the shelf life of pickled foods and increase the chances of using different parts of them as food.
The technology to upgrade these by-products to food is now available, and like meat fillings, protein isolates, hydrolysates and oils that preceded it, could reduce the chances of current practices using it for animal feed, or throwing it away outright in the worst case.
The biggest challenge, however, is that the unsaturated fatty acids found in fish are very sensitive to oxidative degradation, which means that the mass begins to decline after just a few hours. This results in unpleasant tastes, smells, colors, and textures in the final product. The scrap parts of fish, such as skeletons and heads, are rich in blood, and the blood contains the protein hemoglobin, which accelerates the degradation process of fatty acids.
The new technology is based on an impregnation solution containing ingredients such as rosemary extract and citric acid. Within the framework of a European project called WaSeaBi, Ingrid Undeland, along with colleagues Haizhou Wu and Mursalin Sajib, recently published a scientific study exploring the possibilities of the method.
The results showed that immersion of the scraps from the herring sectioning process into the solution before storage greatly prolonged the time before the onset of rancidity, and 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 11 days.
"And, because the macerate is covered with a thin layer of antioxidants on the surface of the side-flow parts, these antioxidants are taken to the next stage of the process, providing more high-quality meat fillings, proteins or oils," explains Ingrid Undeland.
To make the technique cost-effective, the researchers also investigated the possibility of reusing the solution. The results showed that even if the solution was reused up to 10 times, the rancidity phenomenon was completely suppressed at 0 °C. In addition, the researchers found that the solution kept the fish's hemoglobin in a more stable form that reacted less with fatty acids, which the researchers believed was the reason for the reduced oxidation.
The study, which controls hemoglobin-mediated lipid oxidation in clupea harengus by-products by hatching or soaking in a recyclable antioxidant solution, was published in the journal Food Control. It is based on herring by-products from The Swedish Pelialic, however, the results of soaking cod by-products from Royal Greenland also confirm that rosemary-based antioxidant blends are well protected against oxidation. This means that the solution can be used to prevent rancidity of scraps of different species of fish.
Examples from valuable parts of fish include the dorsal spine and head, which are high in muscle and therefore suitable for making surimi or protein ingredients. Since the abdominal flap and intestines are rich in omega-3 fatty acids, they can be used to make oil. The caudal fin has a large amount of skin, bone and connective tissue, so it is suitable for the production of marine collagen, etc., which is currently a highly sought after ingredient on the market. In addition to food, marine collagen is also used in cosmetics and "nutraceuticals" and has a good health effect on the health of our joints and skin.