Quality Assessment of Fish Oil Obtained after Enzymatic Hydrolysis of a Mixture of Rainbow Trout Rest Raw Material Pretreated by High Pressure

Utilization of fish rest raw material for fish oil extraction has received interest with the increasing demand for sustainable food sources. Enzymatic hydrolysis is an efficient method for the extraction of value-added compounds, but its effectiveness may be enhanced by high-pressure processing (HPP). However, HPP can induce lipid oxidation, affecting the quality of the oil. This study aimed to evaluate the quality of fish oil obtained after enzymatic hydrolysis of a mixture of rainbow trout (Oncorhynchus mykiss ) and Atlantic salmon (Salmo salar ) rest raw material pretreated by HPP. Six pretreatments were tested prior to enzymatic hydrolysis; 200 MPa × 4 min, 200 MPa × 8 min, 400 MPa × 4 min, 400 MPa × 8 min, 600 MPa × 4 min, and 600 MPa × 8 min. The oil samples were analyzed for lipid oxidation parameters, free fatty acid content, fatty acid composition, and color changes over 8 weeks. The results confirmed that HPP may induce lipid oxidation and revealed significant influence of HPP parameters on lipid oxidation, with higher pressures leading to increased oxidation. Fatty acid composition varied among samples, but it was not substantially affected by HPP.