Green and efficient extraction of fish oil: Quality optimization based on a deep eutectic solvent method

The efficient extraction of high-quality fish oil with desirable sensory characteristics remains challenging owing to the limitations of conventional techniques such as Soxhlet extraction and enzymatic hydrolysis. In this study, we developed an ultrasound-assisted deep eutectic solvent method (DESM) for extracting bluefin tuna oil and compared its quality and flavor with oils extracted using traditional Soxhlet extraction (SEM) and enzymatic hydrolysis (EH) methods. Through process optimization, the optimal extraction conditions were determined as: ultrasonication temperature of 60 °C, duration of 60 min, power of 200 W, and a solid-to-liquid ratio of 1∶10 ( W / W ). Analyses using an electronic nose, electronic tongue, and volatile compound profiling indicated that the flavor profile of DESM-extracted fish oil was more diverse than that of SEM-extracted oil. Additionally, DESM-extracted oil contained compounds such as caryophyllene and 2-methyl-1-undecanol, which imparted a light greasy taste and a distinctive aroma. In contrast, undesirable odors, including greasy hexanal, strongly greasy 2-hexenal, and bitter almond-like benzaldehyde, were significantly reduced. However, these results reflect instrumental flavor differences rather than direct sensory preference. These findings suggest that DESM has potential for further development as a green fish oil extraction strategy, although additional validation of solvent residue control, storage stability, and sensory acceptability is still required.