Modelling of polyphenoloxidase inactivation by pulsed electric fields considering coupled effects of temperature and electric field

Abstract

Thermal effects can strongly influence the impact of pulsed electric field (PEF) treatment on enzyme inactivation. Most of the kinetic models found in literature, do not distinguish between PEF and thermal effects. A batch PEF treatment chamber with temperature control was used in order to allow performance of PEF treatments at quasi-isothermal conditions. An empirical model describing the PEF polyphenoloxidase (PPO) inactivation as a function of the electric field strength, temperature, treatment time, residence time and synergistic effects of electric field strength and temperature was developed. Experimental data showed that PPO was not inactivated by PEF treatments at temperatures below 55 °C and thermal inactivation seems to be significant at temperatures between 59 and 67 °C. However, PPO activity decreased down to 60% when PEF treatments were applied at temperatures in the range of 55 to 59 °C. The synergistic effect of PEF and temperature was described by a kinetic model at different treatment temperatures. Kinetic models to describe the inactivation of enzymes as a function of PEF parameters, such as electric field strength and treatment time have already been developed. However, these models do not consider the temperature as a variable within the kinetic model. In the present study, a kinetic model was developed, which includes the synergistic effect between temperature and electric field strength. This allows quantifying the PPO inactivation under different processing temperatures and may serve as a base to set up experimental trials whereas a certain temperature is desired.