Supercritical carbon dioxide extraction of cottonseed with co‐solvents

Abstract Extraction of cottonseed lipids with supercritical carbon dioxide (SC‐CO2) was conducted with and without a cosolvent, ethanol or 2‐propanol (IPA). At 7000 psi and 80°C, the reduced pressure, temperature and density of SC‐CO2 was at 6.5, 1.17 and 1.85, respectively; the specific gravity was 0.87. Under these conditions, CO2 is denser than most liquid extraction agents such as hexane, ethanol and IPA. The extraction of cottonseed with SC‐CO2 gave a yield of more than 30% (moisture‐free basis). This is comparable to yields obtained by the more commonly used solvent, hexane. The crude cottonseed oil extracted by SC‐CO2 was visually lighter than refined cottonseed oil. This was substantiated by colorimetric measurements. No gossypol was detected in the crude oil. However, crude oil extracted by SC‐CO2, to which less than 5% of ethanol or IPA as co‐solvent was added, containedca. 200 ppm of gossypol, resulting in the typical dark color of cottonseed crude oil with gossypol. CO2 extracted a small amount of cottonseed phosphatides, about one‐third of that extracted by pure ethanol, IPA or hexane. A second extraction with 100% ethanol or IPA after the initial SC‐CO2 extraction produced a water‐soluble lipid fraction that contained a significant amount of gossypol, ranging between 1500 and 5000 ppm. Because pure gossypol is practically insoluble in water, this fraction is believed to be made up of gossypol complexed with polysaccharides and phosphatides.