Effect of Combined Pressure and Temperature on Soybean Lipoxygenase. 1. Influence of Extrinsic and Intrinsic Factors on Isobaric−Isothermal Inactivation Kinetics

Abstract

Both isothermal and isobaric−isothermal inactivation of soybean lipoxygenase (LOX) could be accurately described by a first-order kinetic model. Thermal inactivation of LOX at atmospheric pressure proceeded in the temperature range 60−70 °C, whereas pressure−temperature inactivation occurred in the pressure range 50−650 MPa at temperatures between 10 and 64 °C. With increasing pressure at constant temperature, a consistent increase in inactivation rate constants was noted, pointing out a negative activation volume. At constant elevated pressure, on the other hand, a temperature of maximum stability was observed, generally situated somewhat above room temperature, indicating the Arrhenius law not to be valid over the entire temperature range. Finally, the influence of some food-relevant intrinsic factors on thermal and pressure−temperature stability of LOX was screened. Where enzyme concentration only slightly affected thermal and pressure stability of LOX, both pH and flushing with CO2 effected significan...