Fish oil extracted from fish-fillet by-products is weakly linked to the extraction temperatures but strongly linked to the omega-3 content of the raw material

Rainbow trout (Oncorhynchus mykiss) is the mainspecies produced in Danish fresh water farming. Therefore, a large amount of fileting by-products like heads, bones, and tails (HBT) and intestines are available and can be used to produce high quality fish oil. The main aim in this study was to investigate whether different extraction temperatures (70 and 90 degrees C) during production of crude fish oil from two fractions (HBT and intestines) separately or together affected the quality of the oil. The quality of the oil was measured by determination of peroxide value, anisidine value, volatile oxidation products, % free fatty acids as well as content of omega-3 PUFA. Furthermore, an experiment was carried out to elucidate the effect of extraction temperature on oil produced from raw materials with a different content of omega-3 fatty acids. For this purpose filleting by-products from conventional (low omega-3 PUFA content) and organic (high omega-3 PUFA content) fish farming were used. Findings showed that the natural variation between production days influenced the quality of the produced oil to a high extent. The temperature was found to play a minor role regarding oxidative quality of the produced oil. However, the omega-3 fatty acid content of the raw material influenced the oil quality. Practical applications: This research was done in industrial scale and shows the results as they were during daily production. Hence, this research is highly relevant for companies and academics who work with fish oil extraction.