Study on the Extraction Conditions of Isoflavones from Soybean Meal and Their Existing Forms in the Extracting Solvent

The extraction conditions of soybean isoflavones from soybean meal with ethanol-water system are studied. The optimum extracting conditions are obtained with orthogonal experimental design method which are solvent 70% ethanol, the ratio of residue mass to solvent volume 0.1 g/ml, temperature 50 ℃, refluent time 1.0 h and extracting 3 times. The existing forms of isoflavones in extracting solvent are researched with acid hydrolysis and isoelectric precipitation. The results show that the unsolvable isoflavones account for 8.0%; sovable isoflavones 92.0%, the isoflavones combined with sugar and protein account for 61.3% and 30.7% respectively. The concentration of isoflavones is determined by HPLC.