Supercritical carbon dioxide extraction of oil and squalene from Amaranthus grain

Supercritical carbon dioxide (SC CO2) was used for the extraction of oil and squalene from Amaranthus grain. Very small amounts of oil could be extracted by SC CO2 from undisrupted grains, although SC CO2 possesses higher diffusivity. Grinding increased the extraction rate and oil yield, and smaller particle size gave higher extraction rate. The oil yield and initial extraction rate increased linearly with the increasing SC CO2 flow rate from 1 to 2 L/min. Increasing the flow rate of SC CO2 above 2 L/min resulted in only a slight increase of oil yield and extraction rate. In the pressure range of 150250 bar, extraction decreased with increasing temperature at a constant pressure, whereas at a pressure of 300 bar, the extraction yield increased with increasing temperature. Possible reasons for this are discussed. Effects of temperature and pressure on squalene yield were different from those on oil yield. A good oil yield (4.77 g of oil/100 g of grain) was obtained at 40 degreesC and 250 bar. The highest squalene yield (0.31 g of squalene/100 g of grain) and concentration (15.3% in extract) were obtained at 50 degreesC and 200 bar, although the oil yield under this condition was low (2.07 g of oil/100 g of grain). The moisture content within 0-10% had little influence on yields of oil and squalene at 40 degreesC and 250 bar. Finally, the oil yield and the squalene concentration in the extracts by SC CO2 were compared to those by solvent extraction.