Chemical characterization and processing suitability of zooplankton-rich side-streams from Atlantic mackerel (Scomber scombrus) processing

Fishmeal and oil have traditionally been used for aquaculture feed but are being replaced by cheaper ingredients. Fish side-streams are now predominantly used in the production of fishmeal and oil and can account for up to 50 % of the raw material. However, due to the increased competition there is a need to look for alternative high-value products from marine side-streams. The aim of the study was to assess the suitability of zooplankton rich side-streams in a pelagic processing plant (side-stream after heading and gutting, and foam from processing water) for further processing, collected in the summers of 2016–2018, and to investigate the effect of catching variables on the chemical composition and lipid quality of these side-streams. The side-stream after heading and gutting was rich in the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), peaking late August, as well as in the monounsatured fatty acid cetoleic acid, C22:1n11. The foam collected from the processing water was rich in monosaturated fatty acids but low in long-chain omega-3 fatty acids. Lipid quality was dependant on the length of the time from catching to processing, with longer time resulting in higher oxidation of lipids. Due to its high lipid content and beneficial fatty acid composition the zooplankton-rich side-stream after heading and gutting is a promising new source of the beforementioned fatty acids and can be recommended to be processed further for human consumption.