Microwave and conventional thermal processing of soymilk: Inactivation kinetics of lipoxygenase and trypsin inhibitors activity

Abstract

Soymilk is an interesting plant-based milk alternative; however, its consumption has been limited due to the presence of antinutritional factors and unpleasant flavor attributed to trypsin inhibitors (TI) and lipoxygenase (LOX) activity, respectively. In this study the application of microwave technology for soymilk processing was evaluated and compared to conventional thermal treatment. Firstly, dielectric and electrical properties of soymilk were assessed at different temperatures to evaluate the penetration depth of the radiation. Then, the inactivation of LOX and TI in soymilk was evaluated after microwave and conventional treatments under different time-temperature combinations. Three kinetic models were adjusted to the experimental data. First-order kinetics with two fractions was the most suitable model to describe LOX inactivation, while for TI inactivation, Weibull model was preferable. Both treatments were equivalent in terms of soymilk LOX and TI inactivation, thus no evidence of additional microwave effects was found. The findings of this study demonstrate that microwave technology has potential for soymilk processing.