Combined thermal and high pressure inactivation kinetics of tomato lipoxygenase

The combined isothermal (10-60 degrees C) and isobaric (0.1-650 MPa) inactivation kinetics of lipoxygenase (LOX) extracted from tomatoes and reconstituted in a tomato puree were studied. Thermal inactivation of LOX at atmospheric pressure proceeded in the temperature range of 45-65 degrees C. LOX inactivation did not follow first order kinetics; the data could be fitted assuming that the two isoforms of LOX with different thermostability were present. Combined thermal and high pressure inactivation occurs at pressures in the range of 100-650 MPa combined with temperatures from 10-60 degrees C, and followed first-order kinetics. In the high-temperature/low-pressure range, (T >= 50 degrees C and P <= 300 MPa) an antagonistic effect is observed, therefore, the Arrhenius and Eyring equation cannot be used over the entire temperature and pressure range. Small temperature dependence is found in the low-temperature/high pressure range. A third degree polynomial model was successfully applied to describe the temperature-pressure dependence of the inactivation rate constants, which can be useful to predict inactivation rate constants of tomato LOX reconstituted in tomato puree in the temperature-pressure range studied.