Tracking isoflavones in whole soy flour, soy muffins and the plasma of hypercholesterolaemic adults

Information on changes in soy isoflavones during processing is needed to better understand the relationship between isoforms, food matrix, bioavailability and health. The abundance and transformation of isoflavones were tracked in soy flour, a baked soy muffin and plasma of hypercholesterolaemic adults (n = 142) who consumed muffins daily for 6 weeks. Isoflavones were identified and quantified in soy flour and muffins by HPLC-UV and in plasma by LC-MS/MS. Equol status was determined and used to assess the relationship between plasma isoflavones and dietary factors. Baking soy flour altered the relative proportion of isoflavone isoforms by promoting a conversion of malonyl- to β-glucosides in soy muffins (P <0.001). Daily soy consumption resulted in >3-fold increase in plasma isoflavones with a doubling of dose (P <0.001). Dietary factors did not correlate with plasma isoflavones. These findings may be used to guide the development of soy-based functional foods.