Abstract: Soy isoflavones were extracted from soy sauce cake, a by-product of soy sauce production, with ethanol aqueous solution, and purified with macroporous adsorption resin AB-8. Using one-factor-at-a-time and orthogonal array design methods, solid-to-solvent ratio was found to have the greatest effect on the extraction of soy isoflavones, and the effect of extraction time was the weakest. The optimal extraction conditions were determined as follows: 70% ethanol aqueous solution as extraction solvent at a solid-to-solvent 1:35 (g/mL) and temperature 80 ℃ for an extraction duration of 3 h. Under these conditions, the extraction yield of soy isoflavones was 1.22%. The soy isoflavone content of the sample purified by adsorption resin chromatography was 41.98%. HPLC analysis showed that soy isoflavone monomers changes slightly.

Key words: soy sauce cake, soyb isoflavone, extraction, purification, absorption resin