Inactivation of Lipoxygenase in Soymilk by Pulsed Light

Inactivation of soybean lipoxygenase in soymilk by pulsed light (PL) at different durations and distances from the pulsed light lamp was determined with and without ice surrounding the soymilk sample tray for cooling. The results show that without cooling, the lowest LOX residual activity was 0.37%, 0.00%, and 7.24%, and with cooling the LOX residual activity was 76.3%, 87.2%, and 69.0% for origin fluence of 302 J/cm , 340 J/cm , and 567 J/cm , respectively. The LOX band reduced or disappeared after PL treatments compared with the LOX band control as assessed by electrophoresis. Peroxide value of the soymilk had no significant increase after pulsed light treatment. This research provided evidence that PL treatment could fully inactivate LOX in soymilk, mostly due to heat generated by the PL strobe, therefore the photo-thermal effect was the main factor that impacted LOX activity.