Comparative Study of Conventional and Emerging Extraction Methods for Papaya Seed Oil: Process Optimization and Quality Evaluation

Papaya seed oil (Carica papaya) is gaining interest for its potential applications as a functional food ingredient. Papaya seeds, usually discarded as agro-industrial waste, represent a valuable source of oil rich in unsaturated fatty acids. This study evaluated several extraction methods, including Soxhlet extraction, maceration, microwave-assisted extraction (MAE), hydraulic pressing, and ultrasound-assisted extraction (UAE), using pure ethanol and pure isopropanol as green solvents. Soxhlet extraction with hexane for 24 h at 121 °C achieved the highest yield (30.91 ± 0.49%) and was used as the reference. Among the greener techniques, UAE performed at 400 W for 30 min with isopropanol achieved the best compromise between yield (22.50 ± 0.27%) and oil quality, showing the lowest acidity index (9.00 ± 2.16 mg KOH/g). Therefore, UAE was selected for further optimization by varying ultrasound power (0–400 W), extraction time (5–30 min), and solvent composition (isopropanol, 50:50 ethanol–isopropanol mixture, and ethanol). The optimal extraction conditions were 200 W for 30 min using a 1:1 ethanol-isopropanol solvent mixture, which resulted in an extraction yield of 26.34%, corresponding to an oil recovery of approximately 85% relative to the Soxhlet reference. The mixed solvent enhanced extraction efficiency by improving mass transfer through the combined effects of solvent polarity and ultrasonic cavitation, confirming that ultrasound-assisted extraction with green solvent mixtures is an effective method for papaya seed oil recovery.