Abstract:

A new technology of combined membrane separation and alcohol precipitation was applied for the purification of isoflavones from the ethanol extract of low-denatured soybean meal. The method for the determination of isoflavone content was developed, and the membrane separation conditions of isoflavones including membrane material type and membrane hole number, membrane regeneration, and the relationship of membrane flux with operation pressure and temperature were investigated. Compared with resin adsorption method, alcohol precipitation was easier to operate and had less process steps and led to higher purity of isoflavones. Alcohol precipitation parameters for the purification of isoflavones were optimized by single-factor and orthogonal array methods. Under the optimized conditions as follows: mass fraction of isoflavone extract 30%, 70% ethanol/material ratio 7:1, stirring time 10 min, adjusting soluble solid content in the supernant after recover of ethanol to 5%, and standing time 5 h, the content of isoflavones in final product was above 60%. An isoflavone yield of 0.7‰ was obtained under the optimized conditions as follows: mass fraction of isoflavone extract 30%, 70% ethanol/material ratio 5:1, soluble solid content in the supernant 8%, and standing time 4 h.

Key words: membrane separation, alcohol precipitation, isoflavone content, technical parameters