Extraction of parboiled rice bran oil with supercritical CO2 and ethanol as co-solvent: Kinetics and characterization

This study aimed to evaluate the behavior of supercritical CO(2 )as solvent and ethanol as co-solvent for obtaining parboiled rice bran oil. The experiments were carried out at different temperatures (40, 60, 80 degrees C), pressures (100, 150, 200 bar) and ethanol to rice bran mass ratios (0:1, 0.5:1, 1:1, 2:1). An extraction using pure ethanol was also performed for comparison purposes. At 100 bar the scCO(2) acted just as a process carrier (and extractions only occurred with the presence of ethanol) while at 200 bar it acted as extractor agent of the process. The highest extraction yield using scCO(2) + Ethanol (obtained on a single run) was 25.48 wt (mass of extracted oil related to the initial mass of rice bran) at 40 degrees C, 200 bar and ethanol to bran mass ratio of 1:1, after 250 min and spending 45.94 g CO2 ( )g(-1) of bran. A slightly higher yield (26.32 wt %) was obtained around three times faster and using less than half of the CO2 by a sequence of two extractions performed at the same conditions of temperature, pressure and initial ratio of ethanol to rice bran. In general, the ethanol addition at the beginning of the process showed to be effective for reducing the necessary time for almost complete extraction. However, applying higher amounts (ethanol to rice bran mass ratio of 2:1) reduced the initial extraction rate. The extracts obtained in this work were also characterized by physicochemical analysis, total phenolic content, antioxidant activity, and thermal analyses.