Author
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King, Jerry |
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Submitted to: Super Green
Publication Type: Proceedings Publication Acceptance Date: 11/6/2002 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The use of pressurized fluids in their sub- or supercritical state provide a versatile medium that are compatible for isolating and processing naturally-derived products in an environmentally benign manner. In addition, by proper selection of the extracting fluid, one can obtain extracts/fractions for direct use as food or nutraceuticals, medical and drug applications, and extracts having cosmetic utility. In this presentation both discrete and serial combinations of sub- and supercritical carbon dioxide with or without ethanol, and sub-critical water with ethanol will be shown to effective solvent combinations for many processes. Supercritical carbon dioxide is well documented as an effective agent for the extraction and processing of many natural product matrices, however addition of up to 20 mole % of GRAS-approved ethanol increases the solubilization of polar solutes. Multi-phase systems consisting of pressurized carbon dioxide with ethanol at pressures beyond 70 MPa also extend the range of applicability of this "green" solvent combination. Water in its hot compressed state (i.e., sub-critical water) provides an alternative solvation medium for the extraction and reaction of polar compounds, while maintaining the naturalness of the resultant extracts. Liquids such as ethanol under pressure and at temperatures above its normal boiling, cover a range of dielectric constant or solubility parameter that are normally attained by using polar and problematic organic solvents. Results will be presented that demonstrate how solute solubility behavior can be altered by application of temperature, addition of ethanol, or naturally-compatible additives to the aqueous phase. Applications of sub-critical water-based extractions or reactions will be demonstrated for naturally-derived compounds, such as anthocyanins from berries at temperatures from 100-150 C. High recoveries (>90%) are achieved for these thermally-sensitive compounds by maintaining a high superficial velocity of the compressed water through the extraction vessel (approx. 0.1 cm/sec) and applied pressures in excess of those required to suppress the boiling tendency of water. Processing schemes based upon the above discrete processes will be illustrated for the selective extraction and reaction of compounds from natural product matrices. When coupled with columnar fractionation, chromatography, and membrane fractionation, the range of applicability of these novel compressed solvents is significantly extended. These combinations then allow the tailoring of the derived extract for its end-use application. |
