Optimizing oil extraction from viscera of Nile tilapia (Oreochromis niloticus) using ultrasound- and microwave-assisted methods: Comparative analysis with wet rendering

• A green technology for high-quality oil extraction was investigated. • Comparison of the influence of different oil extraction was reported. • The most important oil extraction variables were optimized. • Characterization of the extracted Nile tilapia viscera oil was determined. • Oil obtained from Nile tilapia viscera had high quality for value-added products. This study investigates innovative extraction methods to optimize Nile tilapia viscera oil (NTVO) yield and quality, comparing ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and traditional wet rendering method (WRM). The maximum oil yield of 20.29±0.49 % was attained with UAE under conditions of 32 kHz ultrasonic frequency, a 1:6 solid-to-solvent ratio, 50 °C extraction temperature, and 80 min extraction duration. For MAE, the highest yield (18.47±0.43 %) occurred at 180 W microwave power, a 1:8 solid-to-solvent ratio, and an extraction duration of 5 min. Both UAE and MAE demonstrated significantly higher oil yields (18.47±0.43–20.29±0.49 %) and recoveries (71.30±1.16–79.80±1.92 %) compared to WRM, which produced a yield of 6.27±0.10 % and a recovery of 51.22±0.80 %. The extraction method notably affected the physicochemical characteristics and fatty acid profiles of NTVO. UAE yielded the highest oil yield and oxidative stability among the methods tested ( p < 0.05). The predominant fatty acids identified in the obtained NTVO were oleic acid (44.34±1.62–48.68±2.14 %), palmitic acid (17.70±1.16–22.26±0.80 %), and linoleic acid (13.35±0.05–14.38±0.56 %). However, no substantial variation in polyunsaturated fatty acid (PUFA) content was observed among UAE, MAE, and WRM. Overall, UAE demonstrated the highest efficiency for NTVO extraction, offering enhanced technical feasibility and oil quality.