Journal of Food Processing & Technology

Abstract

Investigation on Oil Extraction Methods and its Influence on Omega-3 Content from Cultured Salmon

Deepika Dave, Vegneshwaran VR, Julia P, Sukhinder KC, Sheila T, Heather M and Wade M

Salmon by-products are excellent source of polyunsaturated fatty acids, especially omega-3 and omega-6. The efficiency of different oil extraction techniques from salmon gut, head and frame including enzymatic (30°C for 2 h and 40°C for 4 h) and heat (90°C for 20 min) were compared and the influence on the quality of oil for nutraceutical applications was investigated. The highest oil yield was obtained from the salmon gut (80.01%), head (59.92%) and frame (78.58%) samples treated with enzyme at 30°C for 4 h. The chemical properties including peroxide value, p-anisidine value, TOTOX value, free fatty acid content and acid value were evaluated to determine the salmon oil quality using different methods. The peroxide value (0.28-2.65 meq/kg), p-anisidine value (0.16-1.03), TOTOX value (0.71-10.73), free fatty acid (0.17-1.06%) and acid value (0.33-2.10 mg/KOH g) of all oil samples extracted at different temperature and reaction time were within the recommended limits except for the higher peroxide value (5.26 meq/kg) for the oil extracted from head at 90°C using heat and higher free fatty acid content (1.67-6.49%) and acid value (3.32- 17.49) for the oil extracted from the gut samples. The higher peroxide value was due to interaction between iron-containing protein (myoglobin) and lipid membrane which is released during heat treatment and induces oxidation of lipids. The higher free fatty acid content and acid value in the oil extracted from gut was because of the presence of endogenous enzymes in the gut which causes rapid autolysis of gut tissues during processing and oil extraction. The oils extracted using different methods were analyzed for the fatty acid content. The salmon gut, head and frame oil contains saturated fatty acids (19.21-21.93 g/100 g), monounsaturated fatty acids (36.82-40.17 g/100 g) and polyunsaturated fatty acids (38.89-39.83 g/100 g). The total omega 3 and omega 6 fatty acids present in the salmon gut, head and frame was in the range of 23.41-25.73 g/100 g and 10.27-12.03 g/100 g, respectively. The ratio of omega 3/omega 6 fatty acids present in the salmon gut, head and frame was in the range of 1.96-2.50 g/100 g. The ratio of DHA/EPA present in the salmon gut, head and frame was in the range of 0.95-1.07 g/100 g. The oil extracted using enzymatic methods had slightly higher fatty acid content than the heat extracted oil. The preliminary quality analysis of the oil extracted from different salmon parts at different temperatures and reaction times and the presence of higher EPA, DPA and DHA suggested that the oil had good quality standards; it is not oxidized and can be subjected to various nutraceutical applications.