In this work, aqueous extraction of rice bran oil was done without and with ultrasound pretreatment. Key
factors controlling the extraction and optimal operating conditions were identified. The highest extraction
efficiency was found at pH = 12, temperature of 45 C, agitation speed of 800 rpm and agitation time
of 15 min, ultrasound treatment time of 70 min and ultrasound treatment temperature of 25 C.
Moreover, extraction yields were compared to ultrasound-assisted aqueous extraction and Soxhlet
extraction. The results showed that the yield of rice bran oil at ultrasound-assisted aqueous extraction
was close to the yield of oil extracted by hexane Soxhlet extraction. This result implied that the yield
of rice bran oil was significantly influenced by ultrasound. With regard to quality, the oil extracted by
ultrasound-assisted aqueous process had a lower content of free fatty acid and lower color imparting
components than the hexane-extracted oil. Also, effect of parboiling of paddy on hexane and
ultrasound-assisted aqueous extraction was studied. Both extraction methods gives higher percentage
of oil from par boiled rice bran compared with raw rice bran. This may be due to the fact that parboiling
releases the oil.