Kinetic modeling of the conversion and losses of isoflavones during soybean soaking

Abstract

The objective of this study was to solve the first-order kinetic models of interconversion and losses of isoflavones, expressed as differential equations, by Laplace transform method. The kinetic models were applied to investigate the changes in the contents of different forms of isoflavone (malonylglucosides, β-glucosides, and aglycones) during soybean soaking at various temperatures (25 °C, 40 °C, 55 °C, and 70 °C). Soaking at 25 °C did not influence the contents of isoflavones of the daidzein, glycitein, and genistein series. A higher hydrolysis rate constant, which corresponds to the conversion of β-glucosides to aglycones, was observed at 55 °C due to the action of endogenous β-glucosidase. However, at 70 °C, there was a decrease in the hydrolysis rate. All isoflavone forms of the genistein and daidzein series were thermally stable during soybean soaking at 70 °C. A mathematical modelling of the kinetics provided better insights into the mechanisms of interconversion and losses of the isoflavones.