| Summary: | Pelagic fish such as Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus) feed mostly on zooplankton, like Calanus finmarchicus and krill, which are rich in valuable ingredients, including wax esters, polyunsaturated fatty acids and astaxanthin. Large amounts of these zooplanktons follow pelagic catches as part of the stomach content and can be considered a side-catch. These zooplankton-rich side-streams could be processed further for high-quality oils with astaxanthin in them. The aim of this project was to investigate the efficiency of applying solvent winterization at three different temperatures (0, -24 and -35°C) on oils extracted from zooplankton- rich side-streams from Atlantic herring and mackerel processing, with the overall aim to increase separation between fatty acid groups and to increase the EPA and DHA content of the liquid phase. Zooplankton-rich side-streams of herring and mackerel entering a fish meal processing facility were separated into zooplankton-rich sieve-water (ZRW) and viscera which were sampled and characterized for both species. Foam was also collected from the foaming tank at the end of a processing water treatment system. Oils were extracted from the samples, as well as from mackerel and herring muscle for comparison. All oils were then winterized with a solvent at 0, -24 and -35°C and the fatty acid composition of the obtained liquid and crystallized phases were analyzed. ZRW and foam from mackerel were higher in eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA) content than ZRW and foam from herring and are therefore more suitable for the production of higher quality oils. ZRW and foam from herring were higher in cetoleic acid than ZRW and foam from mackerel and could be used for fish feed oils. Winterizing ZRW in acetone from mackerel at -35°C gave higher proportion of EPA and DHA (29.2 ± 0.0%) content than at -24°C (27.7 ± 0.1 %), however higher proportion of the oil crystalizes at -35°C (65.8 ± 1.6 %) compared to -24°C (19.5 ± 1.1 %). The ...
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