Abstract: Millet bran oil was extracted and rectified with supercritical fluid carbon dioxide (SFCO2). In the extraction, pressure, temperature, length of extraction time and CO2 flow rate were optimized by orthogonal array design, and the influences of pressure and temperature on the rectification of millet bran oil were analyzed. The results showed that the optimal conditions for the extraction of millet bran oil were as follows: extraction at 45 ℃ for 2 h under 30 MPa with a CO2 flow rate of 50 kg/h, the resultant oil yield was up to 19.69% under these conditions, and the optimum rectification conditions were 10 MPa column pressure and the temperatures of 40, 45, 50 ℃ and 55 ℃ for four sequential columns. The millet bran oil prepared in this study contained a relatively large amount of unsaturated fatty acids, especially linoleic acid up to 67.8%, and had better physical and chemical indexes in comparison with commercial ones.

Key words: millet bran oil, supercritical CO2, extraction and rectification