Kinetics of pressure inactivation at subzero and elevated temperature of lipoxygenase in crude green bean (Phaseolus vulgaris L.) extract

Lipoxygenase (LOX) in crude;green bean extract was irreversibly inactivated by pressure treatments combined with subzero or elevated temperature. LOX inactivation was described accurately assuming a first-order reaction. In t he entire pressure-temperature domain studied (200 to 700 MPa and -10 to 60 degrees C), an increase in pressure at constant temperature enhanced the L OX inactivation rate, whereas at constant pressure, an increase in reaction rate was obtained by either increasing or decreasing temperature at 20 deg rees C. At elevated pressure, LOX exhibited the greatest stability around 2 0 degrees C. Also the pressure dependence of the inactivation rate constant s for LOX was the highest around 20 degrees C. On the basis of the estimate d LOX inactivation rate constants, an iso-rate contour diagram as a functio n of pressure and temperature was constructed, and an empirical mathematica l model describing the combined pressure-temperature dependence of the LOX inactivation rate, constants was formulated.