Supercritical CO 2 extraction of lipid‐bearing materials and characterization of the products

Abstract Supercritical fluid extraction has recently become a reality in the petroleum, coal and food industries and is rapidly increasing in importance as its advantages become known. Advantages of carbon dioxide as a supercritical fluid include its low toxicity, low cost, lack of flammability, lack of reactivity, wide range of solvent properties at different pressures and temperatures, and improved properties of separated components in certain cases. Disadvantages of such extractions include high capital costs for batch extraction and lack of engineering hardware technology for continuous operation. In the supercritical CO 2 extraction of oil from soybeans, equilibrium solubility and high flow rates are readily achieved in a short‐path batch reactor. The oil has a lighter color, less iron and ca. 1/10 of the phosphorus contained in hexane‐extracted oil. The lower phosphorus content results in lower refining losses. During extraction, some fractionation is observed to take place, with some more polar and/or higher molecular weight compounds having a tendency to increase in the later fractions. In a long cylindrical batch extractor, the flakes perform much like the stationary phase of a chromatographic column. The same advantages that result from extraction of soybeans also apply to the extraction of oil from cottonseed and corn germ. Cottonseed oil obtained by supercritical CO 2 extraction has a lower gossypol content and requires less alkali for refining. In the extraction of wheat germ and bran, the oil has a lighter color, a milder odor and less unsaponifiables than that obtained by hexane. Free fatty acid contents were comparable, but tocopherol was higher in the supercritical CO 2 extract.