Effects of Oil Extraction Methods on Physical and Chemical Properties of Red Salmon Oils (Oncorhynchus nerka)

The following four methods were used to extract salmon oil from red salmon heads: RS1 involved a mixture of ground red salmon heads and water, no heat treatment, and centrifugation; RS2 involved ground red salmon heads (no water added), heat treatment, and cen- trifugation; RS3 involved a mixture of ground red salmon heads and water, heat treatment, and centrifugation; and RS4 involved ground red salmon heads, enzymatic hydrolysis, enzyme inactivation by heat and centrifugation. The four extracted oil samples were evaluated for chemi- cal, thermal, and rheological physical properties. The RS4 process recovered significantly higher amounts of crude oil from red salmon heads than the other three extraction methods, while containing a higher % of free fatty acids and higher peroxide values than RS1, RS2, and RS3 oils. Oleic acid, eicosenoic acid, EPA, and DHA were the pre- dominant fatty acids accounting for about 60% of all unsaturated fatty acids. The RS1, RS2, RS3, and RS4 extractions contained 9.3, 9.05, 9.35, and 9.45% of EPA and 8.8, 8.55, 9.0, and 9.1% of DHA in the oil, respec- tively. Weight losses of the oils increased with increasing temperatures between 200 and 500 C. The % weight losses at 500 C were 94.50, 94.58, 94.94, and 95.47% for RS2, RS1, RS3, and RS4, respectively. The apparent vis- cosities of all the oil samples decreased with the increases in the temperature. The RS1 extract was more viscous (P \ 0.05) than those of RS2, RS3, and RS4 between 0 and 25 C.