Inactivation of Yersinia enterocolitica by pulsed electric fields Original Research Article

The influence of growth conditions, treatment medium characteristics and PEF process parameters on the lethal effect on Yersinia enterocolitica of pulsed electric fields (PEF) treatments in batch has been investigated. Growth phase, temperature of growth, pH, conductivity of the treatment medium, pulse width and frequency of pulses did not influence the sensitivity of Y. enterocolitica to PEF. However, an Aw decrease from >0.99 to 0.93 of the treatment medium increased the PEF resistance of Y. enterocolitica with 3.5 log10 cycles after a treatment of 22 kV/cm, 800 μs and 880 kJ/kg. Inactivation of Y. enterocolitica increased with the field strength, treatment time and total specific energy up to a maximum of 6 log10 cycles after 28 kV/cm, 2000 μs and 3559 kJ/kg. A nonlinear relationship was found among the survival fraction and the treatment time or the specific energy that was accurately described by a mathematical model based on the Weibull distribution. The inactivation of Y. enterocolitica by PEF was characterized by maximum field strength thresholds. Above these thresholds, specific energy necessary to obtain a given level of inactivation scarcely decreased by increasing the electric field strength, and inactivation of Y. enterocolitica only depended on the specific energy applied.