Supercritical CO2 extraction of rice bran

Extraction of rice bran lipids with supercritical carbon dioxide (SC‐CO2) was performed. To investigate the pressure effect on extraction yield, two isobaric conditions, 7000 and 9000 psi, were selected. A Soxhlet extraction with hexane (modified AOCS method Aa 4–38; 4 h at 69°C) was also conducted and used as the comparison basis. Rice bran with a moisture content of 6%, 90% passable through a sieve with 0.297 mm opening, was used for extraction. A maximum rice bran oil (RBO) yield of 20.5%, which represents 99+% lipid recovery, was obtained with hexane. RBO yield with SC‐CO2 ranged between 19.2 and 20.4%. RBO yield increased with temperature at isobaric conditions. At the 80°C isotherm, an increase in RBO yield was obtained with an increase in pressure. The pressure effect may be attributed to the increase in SC‐CO2 density, which is closely related to the value of the Hildebrand solubility parameter. RBO extracted with SC‐CO2 had a far superior color quality when compared with hexane‐extracted RBO. The level of sterols in SC‐CO2‐extracted RBO increased with pressure and temperature.