Comparison of conventional and green extraction methods on oil yield, physicochemical properties, and lipid compositions of pomegranate seed oil

This study aimed to evaluate the effects of conventional (Soxhlet; shaking extraction, SE) and green methods (microwave-assisted extraction, MAE; ultrasound-assisted extraction, UAE; subcritical extraction, SubE) on the oil yield, physicochemical properties, and lipid compositions of pomegranate seeds oil (PSO). The oil yield ranged from 11.32% to 15.66%, and the highest yield was obtained by Soxhlet. The results indicated that no significant differences (p > 0.05) were observed in refractive index and specific gravity of oils among different methods. PSO was abundant in polyunsaturated fatty acids. MAE and SubE samples exhibited comparatively higher contents of punicic acid (776.5 and 772.3 mg/g, respectively). Twelve triacylglycerol molecules were detected, in which punicic acid-punicic acid-punicic acid occupied the most proportion (47.85–48.51%). Lipid concomitants in PSO mainly contained squalene (1.20–1.72 mg/g), β-sitosterol (3.23–3.67 mg/g), and tocopherols (348.2–359.8 mg/100 g). Three tocopherols (α, γ, and δ) were identified in PSO with the dominance of γ-tocopherol (322.7–329.4 mg/100 g). UAE obtained relatively higher squalene and β-sitosterol contents, whereas SubE resulted in the highest tocopherol content in oils. These results demonstrated the technical feasibility of green extraction methods for obtaining PSO with high nutritional and valuable compounds.