Production of salmon oil from filleting byproducts--effects of storage conditions on lipid oxidation and content of omega-3 polyunsaturated fatty acids

Filleting byproducts (heads, frame bones, skin, and down-graded gutted fish) from farmed Atlantic salmon (Salmo salar) were separated into a solid/aqueous phase and a lipid phase (oil) using a scraped-surface heat exchanger (90 degrees C to 95 degrees C) and a decanter centrifuge (93 degrees C). Effects of storage temperature (4 degrees C and 23 degrees C), atmosphere (air and N2), and time (0 to 180 d), as well as an additional process step-a separator introduced after the decanter centrifuge, were investigated on the quality and storage stability of the produced oil. Samples were analyzed for the quality parameters peroxide (PV), anisidine (AV), and Totox value (TxV), content of free fatty acids (FFA), content of fatty acid methyl esters (FAME), especially the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and degradation of EPA and DHA related to the content of hexadecanoic acid (HDA) (ratios EPA/HDA and DHA/HDA). Storage temperature had significant effect on all the investigated quality parameters, especially on AV, PV, and TxV where a high storage temperature (23 degrees C) caused a 10-fold, 2.5-fold, and 4-fold increase in AV, PV, and TxV, respectively. Storage atmosphere had significant effect on all the investigated parameters, except on the DHA/HDA ratio, where storage under an N2 atmosphere significantly preserved the quality of the oil compared with storage in air. Generally, no significant effect of storage time on the investigated quality parameters was observed before 120 d of storage. No effect on quality was observed when introducing an additional processing step (separator) after the decanter centrifuge. Salmon oil is a stable product, and even more so when stored at appropriate conditions (under nitrogen atmosphere at refrigerated temperatures).