Heat treatment of Pink Salmon (Oncorhynchus gorbuscha) Fractions - Effect on Lipid and Liquid Release

The global demand for fish oil and fish protein hydrolysate (FPH) continues to rise, driven by their health benefits and versatile applications. Traditional extraction methods tend to prioritize one product over the other, resulting in inefficiencies and reduced overall quality. Moreover, during enzymatic hydrolysis, the high lipid content can lead to the formation of an emulsion layer that hinders the overall extraction process of FPH. This master thesis addresses these challenges by focusing on the extraction of high-quality oil from pink salmon (Oncorhynchus gorbuscha) and its by-products using thermal treatment at controlled temperatures. The goal is to achieve high oil yields with minimal protein denaturation, allowing the lipid-depleted material to serve as a source for enzymatic hydrolysis to produce FPH. Pink salmon, often considered an invasive species in several countries due to its growing population in local rivers, poses a threat to native species and ecosystems. However, this also presents a significant opportunity to utilize pink salmon and its by-products for human consumption and FPH production. The analyses of the proximate composition of pink salmon fillet, head, and spine revealed a high lipid and protein content comparable to other valuable species like Atlantic salmon. This analysis provided a strong foundation for exploring the efficiency of oil extraction through thermal treatment. The samples, which were frozen and thawed before thermal treatment, exhibited some protein denaturation, as evidenced by the analysis of water-soluble and salt-soluble protein content through gel electrophoresis. Thermal treatment was conducted at temperatures ranging from 30°C to 80°C, followed by centrifugation to separate the oil, liquid, and leftover materials. The oil content, measured against the lipid content of the raw material, yielded less than 8% of the total lipid content, which was lower than expected. The oil extracted during thermal treatment was rich in essential fatty acids, including significant amounts of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) such as EPA and DHA. These fatty acids, which were also found in the by-products, underscore the potential of pink salmon as a valuable source for future omega-3 oil production. Interestingly, the liquid separated during centrifugation exhibited gelling properties, and had a collagen content of 0.042 milligrams per gram, suggesting its potential for use in food processing ap