KINETICS OF COMBINED PRESSURE-TEMPERATURE INACTIVATION OF AVOCADO POLYPHENOLOXIDASE

Irreversible combined pressure-temperature inactivation of the food qu ality related enzyme polyphenoloxidase was investigated. Inactivation rate constants (k) were obtained for about one hundred combinations of constant pressure (0.1-900 MPa) and temperature (25-77.5 degrees C). According to the Eyring and Arrhenius equation, activation volumes and activation energies, respectively, representing pressure and temperat ure dependence of the inactivation rate constant, were calculated for all temperatures and pressures studied. In this way, temperature and p ressure dependence of activation volume and activation energy, respect ively, could be considered. Moreover, for the first time, a mathematic al model describing the inactivation rate constant of a food quality-r elated enzyme as a function of pressure and temperature is formulated. Such pressure-temperature inactivation models for food quality-relate d aspects (e.g., the spoilage enzyme polyphenoloxidase) form the engin eering basis for design, evaluation, and optimization of new preservat ion processes based on the combined effect of temperature and pressure . Furthermore, the generated methodology can be used to develop analog ous kinetic models for microbiological aspects, which are needed from a safety and legislative point of view, and other quality aspects, e.g ., nutritional factors, with a view of optimal quality and consumer ac ceptance. (C) 1998 John Wiley & Sons, Inc.