Highly efficient extraction of EPA/DHA‐enriched oil from cobia liver using homogenization plus sonication

Cobia, Rachycentron canadum, is a species of marine finfish with emerging global potential for offshore aquaculture. The fillet processing by‐product, cobia liver, can be considered an accessible source of EPA/DHA‐enriched oil. Oils are mainly extracted with hexane in the oil industry; however, extractability is greatly decreased in wet biomass as the hydrophilic surface hinders the penetration of hexane into the tissue matrix. In this study, the feasibility of agitated extraction (AE), ultrasonic extraction (UE), Soxhlet extraction (SE), homogenizer extraction (HE), and homogenizer extraction plus sonication (HES) was evaluated. HE and HES showed higher extraction efficiency than AE, UE, or SE. The highest yields: 45.7% and 50.2%, were obtained from using HE for 2 min and HES for 120 min, respectively. Both yields were close to the fat content of cobia liver, indicating that the lipids were effectively extracted. The fatty acid profiles revealed that the highest contents of 5.2% eicosapentaenoic acid (EPA) and 19.7% docosahexaenoic acid (DHA) were obtained from HE and HES, respectively. These results demonstrated that HE and HES were highly efficient and the most useful among all tested methods for lipid extraction from wet biomass. Practical applications: Increasing the value of low quality processing waste is important in the food and nutraceutical industries. Cobia liver, comprising 5% of total fish mass, is a potential source of EPA/DHA‐enriched fish oil. EPA and DHA decompose easily when exposed to high temperatures for a long time. HE has an advantage over traditional extraction methods due to its ability to operate at a low temperature for a short period (2 min), thereby preventing EPA and DHA decomposition. Cobia are already bred in the aquaculture industry; their livers are readily available by‐products obtained after fillet processing. The oils extracted from cobia liver have high levels of EPA and DHA, therefore it is an excellent raw material to produce EPA/DHA‐enriched oil. Wet biomass contains a high amount of moisture, creating mass transfer resistance for hexane penetration into the tissue matrix. Homogenizer extraction grinds the tissue matrix, disrupting the cell and dispersing the water into solvent phase. Schematic representation of the extent of cell disruption during homogenizer extraction shows its effect on the rate of lipid release.