Comparison of Supercritical Fluid Extraction and Solvent Extraction of Isoflavones from Soybeans

Supercritical fluid extraction (SFE) with supercritical carbon dioxide and solvent extraction of isoflavones from soybeans were investigated. Extraction efficiencies under several different extraction conditions were examined. For SFE, pressure, temperature, organic modifier content, were optimized. The best extraction conditions were 55C, 100bar, and 7.5% ethanol modifier. Extraction recoveries of daidzein (97.3%) and genistein (98.0%) were obtained. For the solvent extraction, with 30mL of 1N HCL and 80% ethanol, daidzein of 676.3g/g and genistein of 659.9g/g were extracted. Data shows that SFE gives a little lower isoflavones recovery compared to conventional extraction with organic solvents. However, the SFE method has several advantages over the solvent extraction method. Sample handling steps are minimized, thus reducing possible losses of analytes and saving analysis time. No cleanup steps are employed, and no organic solvent extractions are involved in this method.