Ultrasound assisted extraction of fish oil from fish waste with and without enzyme

For the purpose of oil extraction from gilthead seabream (Sparus Aurata) by-products, ultrasound-assisted solvent extraction (UASE) and ultrasound-assisted enzymatic extraction (UAEE) were studied. Response surface methodology was applied to the models to optimize the conditions for maximum oil efficiency using five level three factor central composite design for each method. For UASE, chosen factors were time (5–70 min), temperature (25–60℃), and solid-solvent ratio (4–20 mL/g). Optimum conditions were 37.63 min ultrasound time, 42.55⁰C temperature, and 1:15.47 solid-solvent ratio with the desirability of 1.00 where the highest oil efficiency was 38.11%. Factors for UAEE were hydrolysis time (0.5–6h), enzyme concentration (0.10–2.5%), and ultrasound time (1.5–45 min). Optimum conditions were 4.88h hydrolysis time, 0.58% enzyme concentration, and 10.31 min ultrasound time with the desirability of 0.942 where the highest yield was 30.76%. At optimum conditions, oils extracted by UASE showed higher extraction yield, lower acidity value, and better oxidation stability as compared to UAEE. As a result, the physicochemical and oxidation analyses of fish oils confirmed the suitability of both UASE and UAEE for the recovery of high-quality oils from fish processing by-products.