Study On Extraction Of Soy Isoflavones From Soybean Meal

Supercritical fluid extraction and solvent extraction of soybean isoflavones from soybean meal were studied in the present thesis. The mathematical model of supercritical fluid extraction and solvent extraction were also established. The method of quantifying isoflavones in extracts using HPLC was established with Waters 1525 system.Aqueous ethanol was employed in solvent extraction method. Based on single-factor experiments, orthogonal experiments were performed to optimize the extractive conditions. Based on range analysis of the experimental data, the optimized conditions of extraction were: 70% ethanol, solvent/sample ratio of 1:20, temperature of 70℃and 4 hours extraction. The largest amount of total isoflavones obtained was 2668.4μg/g.According to Fick's second law, the dynamic model of solvent extraction of isoflavones was established. Considering the degradation reaction of isoflavones, the kinetic equation was modified. The model accuracy was improved.With aqueous ethanol as modifier, supercritical fluid extraction experiments were undertaken to investigate systematically the influence of the modifier composition, the modifier concentration, the particle size and the conditions of extraction (temperature, pressure, CO₂ flow rate and time). The orthogonal experiments were undertaken to optimize the conditions of extraction.Aqueous methanol was also adopted to improve the extraction efficiency of total isoflavones. Optimized conditions of 40℃, 60 MPa, CO₂ flow rate of 10 L/h and 270 minutes was gotten and the yield was 2458.8μg/g.Based on the hypothesis of adsorption-desorption equilibrium of solute in matrix pores, an adsorption-desorption mathematical model was established involving only one parameter, adsorption equilibrium coefficient, to be regressed from the experimental data. The deduced model fitted the experimental data very well.