Inactivation of soybean lipoxygenase in soymilk by pulsed electric fields

Abstract

The inactivation of soybean lipoxygenase by pulsed electric fields (PEF) was studied. Effects of PEF parameters (treatment time, pulse strength, pulse frequency and pulse width) were evaluated. Soymilk was exposed to pulsed strengths from 20 to 42kV/cm for up to 1036μs treatment time in square wave pulse of bipolar mode. Moreover, pulse frequency (100–600Hz) and pulse width (1–5μs) was also tested at constant pulsed treatment time of 345μs and strength of 30kV/cm. Residual activity of soybean lipoxygenase decreased with the increase of treatment time, pulse strength, pulse frequency and pulse width. The maximum inactivation of soybean lipoxygenase by PEF achieved 88% at 42kV/cm for 1036μs with 400Hz of pulse frequency and 2μs of pulse width at 25°C. Inactivation of soybean lipoxygenase by pulsed electric fields was modeled using several kinetic models. Weibull distribution function was most suitable model describing the inactivation of soybean LOX as a function of pulsed electric fields process parameters. Moreover, reduction of soybean LOX activity related to the electric field strength could be well described by the Fermi model.