4. CONCLUTION
It may be concluded that the different extraction methods modify the physicochemical properties, nutrient substances, and volatile compounds of Qingjinju seed oils. The oil yield obtained by solvent extraction (35.07%) was higher than that of screw press (31.04%) and supercritical CO2 (27.69%) extraction. Specific gravity, refractive indices, acid values, peroxide value, and unsaponifiable matters of SO were lower than that of SPO and SCO, suggesting that SO possessed superior physicochemical properties. The Qingjinju seed oils consisted of major fatty acids including oleic acid (34.08-35.49%), linoleic acid (29.79-30.79%), palmitic acid (17.17-17.76%), stearic acid (8.02-8.94%), and linolenic acid (6.50-6.81%), making the oil a good source of unsaturated fatty acids. SPO and SCO contained limonin (3544.63 mg/kg, 3052.96 mg/kg) and nomilin (534.90 mg/kg, 673.13 mg/kg), which were underrepresented in SO (722.49 mg/kg, 65.02 mg/kg). Supercritical CO2 and screw press extraction were therefore more beneficial for retaining the limonoid content in Qingjinju seed oils. The volatile compounds of SPO and SCO were primarily aldehydes, while hydrocarbons were the major volatile class in SO. The seven main volatile compounds were identified across the extraction methods. Qingjinju seed oils could provide valuable stock oil for food or chemical industries and different extraction methods can be selected according to their intended use.