Abstract: Rice germ oil rich in tocopherol was extracted by ultrasonic-assisted aqueous enzymatic method. Under the following conditions: mass ratio of cellulase to neutral protease 1:1, enzyme concentration 1.2%, material-to-liquid ratio 1:5, and hydrolysis time 3 h, the extraction efficiency was (87.4 ± 0.04)%. Through transmission electron microscopy, it was found that obvious separation was observed between fat and protein after ultrasonic treatment of rice germ. Response surface analysis showed that ultrasonic power had the greatest effect on the extraction efficiency, followed sequentially by temperature and duration. Under the conditions of temperature of 55 ℃, ultrasonic power of 400 W, and time of 20 min, the extraction efficiency of rice germ oil was (92.1 ± 0.03)%. Saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids accounted for (20.62 ± 0.14)%, (39.62 ± 0.96)% and (37.46 ± 0.43)% of the total fatty acids in rice germ oil extracted by the ultrasonic-assisted aqueous enzymatic method, respectively. The contents of γ-oryzanol, phytosterols and total tocopherols in the oil were (490.00 ± 2.12), (384.19 ± 5.14) and (93.01 ± 2.75) mg/100 g, respectively.

Key words: rice germ oil, ultrasonic, aqueous enzymatic method, solvent-free, extraction efficiency