Abstract
Rice bran oil (RBO) contains oryzanol and tocopherols. Its recovery was performed using conventional techniques with toxic solvents that leave residues in the final product. Supercritical fluid extraction (SFE) has been used, obtaining high global yields without residual solvent. This work proposes to use ultrasound to enhance the kinetics of the RBO extraction using supercritical CO2. The factors considered were ultrasound power (160 to 320 W) and sonication time (40 to 120 min), at 40 ºC and 25 MPa. The best condition (160 W / 40 min) resulted in a 12.65 wt% extraction yield. When ultrasound was not used, the global yield dropped to 9.94 wt%, representing an increase of 27% of global yield due to ultrasound application. This increase can be assigned to the vibration effect promoted by the ultrasonic waves at the interfaces between the solid matrix and solvent. The extracts showed antioxidant activity towards the DPPH radical achieving values around 70% of inhibition. Precursors of oryzanol (campesterol, β-sitosterol, stigmasterol and 4-methylenecycloartanol) were identified in the SC-CO2 + US extracts. The results presented herein showed that SC-CO2 + US is a promising technology to be employed for the extraction of bioactive compounds.
Keywords:
Oryzanol; Antioxidant activity; Scanning electron microscopy; Byproduct
