Thermal inactivation kinetics of peroxidase and lipoxygenase from fresh pinto beans (Phaseolus vulgaris)

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 Thermal inactivation kinetics of crude peroxidase (POX) and lipoxygenase (LOX) in fresh pinto beans were studied over the temperature range of 55–90°C. The inactivation of both enzymes followed first-order kinetics. The biphasic inactivation curves for POX indicate the existence of several isoenzymes of varying heat stability. In the temperature range of 55–70°C, the activation energies (E a) of POX were 46.5 kcal·mol–1 for the heat-labile portion and 37.6 kcal·mol–1 for the heat-stable portion. On the other hand, the LOX enzyme had an E a value of 42.26 kcal·mol–1 at 55–75°C and 49.1 kcal·mol–1 at 55–90°C.

Received: 28 July 1997 / Revised version: 16 October 1997