Petroleum-free extraction of oil from soybeans with supercritical CO2
1982
Friedrich, J.P. | List, G.R. | Heakin, A.J.
Full-fat soyflakes are readily extracted with supercritical carbon dioxide (SC-CO2) at pressures of 3,000~10,000 psig and 50 C. Under these conditions, SC-CO2 has the density of a liquid and the diffusivity of a gas. Therefore, equilibrium solubility is readily achieved in a short-path batch extractor which permits high gas flow rates. Soybean oil extracted with SC-CO2 is lighter in color and contains less iron and about one-tenth the phosphorus of hexane-extracted crude oil from the same beans. The lower phosphorus content is reflected in a chromatographic refining loss of 0.6% compared to 1.9% for hexane crude. Refined oils from hexane and SC-CO2 extraction had equivalent odor and flavor scores initially and after 4 days' storage at 60 C. Carbon dioxide, an ideal solvent for extraction of food products, is low-cost and readily available from fermentation processes and could free over 20 million gallons of costly hexane per year for essential energy uses.
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