Characterization of Isoflavones in Membrane-processed Soy Protein Concentrate

ABSTRACT: Aqueous soy flour solutions (5% w/w) were treated for 3 h at 45 to 50 °C with Crystalzyme®, without enzyme at 45 to 50 °C, or blanched at 80 °C. Solutions were ultra‐ and dia‐filtered to produce membrane soy concentrates (MSC). Total isoflavones of MSCs were 3.02 mg/g, 3.12 mg/g, or 3.42 mg/g, respectively, on a dry weight basis. Membrane processing contributed to approximately 18, 15, or 8% decreases, respectively, in total isoflavones of MSCs compared with soy flour (3.71mg/g). This represents at least an 82% recovery. There was no significant difference in total isoflavone content in any MSC, however the profile of isoflavones as glucosides or aglycones changed with treatment conditions.