Effects of ultrasound-assisted extraction (UAE) conditions viz., ultrasound power and treatment time on extraction efficiency and quality of oil from rice bran were studied. The sonication power and irradiation time varied between 6.11, 12.23, and 18.35 W/cm2; and 5, 15, and 25 min, respectively. The recovery, physicochemical and phytochemical properties of UAE oil were measured and compared with conventional soxhlet extraction (SE) and pressurized liquid extraction methods (PLE). The results showed that increasing the ultrasonic irradiation time and power led to greater oil extractability. However, the oil quality and ultrasonic intensity were inversely correlated. Specifically, higher power intensity (18.35 W/cm2) and longer irradiation time (15-25 min) impaired the unsaturated fatty acids (UFAs) and phytochemical compositions of the extracted oil. The maximum oil extractability obtained by PLE and UAE (12.23 W/cm2 and 15 min) were 16.77 mg/g rice bran and 16.59 mg/g rice bran, respectively, and higher than the SE process (14.96 mg/g rice bran). No significant differences were shown among PLE and UAE (12.23 W/cm2 and 15 min) oils for the physiochemical and phytochemical properties. Similar to the PLE and SE oils, oleic acid was the dominant fatty acid in the UAEs oils, followed by linolenic and palmitic acids. Scanning electron microscopy (SEM) results showed that the UAE process effectively damaged the cell walls of rice bran, resulting in improved oil yield. Thus, UAE is a promising method for extracting oil from rice bran.
Keywords: rice bran oil; fatty acids; soxhlet extraction; the pressurized liquid extraction; ultrasound assisted solvent extraction
*Corresponding author: E-mail: pvman.dbv@moet.edu.vn
