Valorization of whole herring (Clupea harengus) through trimming, mincing and antioxidant washing: Enhancing stability and color for food use

Turning the valorizing of small herring ( Clupea harengus ) from primarily being a feed resource into being a valuable food ingredient requires strategies to overcome rapid lipid oxidation, dark color and processing losses. This study investigated trimming (deheading plus partial gutting or, deheading plus full gutting) and washing of mechanically separated meat (MSM) to improve oxidative stability and appearance of whole herring while maintaining maximum processing yields. Trimming reduced hemoglobin content and lipoxygenase activity gradually by up to 73% and 75% (dw), respectively, yet lipid oxidation was initiated within 1 day on ice for all samples. Washing MSM once or twice (1:3 ratio) further decreased these pro-oxidative factors but had limited effect on oxidation onset. Incorporating a rosemary-based antioxidant blend (0.5%) into the wash water delayed the start of oxidation to more than 11 days. Sufficient oxidative stability was achieved with a single antioxidant-assisted wash, which also minimized water use and processing losses of proteins and lipids. In terms of color, trimming and consecutive washes progressively increased lightness, while antioxidant-assisted washes also helped maintaining redness during storage. Correlation analysis revealed that lipid oxidation was more strongly associated with hemoglobin, lipoxygenase, and pre-formed hydroperoxides than total lipid content, highlighting these factors as important mitigation targets for the food industry. By combining targeted trimming with antioxidant-assisted washing, the oxidative stability, color, and processing efficiency of herring MSM can be improved, supporting a sustainable upcycling of small pelagic fish into nutritious food and thereby steering away from their current main use in feed production.