Influence of treatment temperature on the inactivation of Listeria innocua by pulsed electric fields

The effect of treatment temperature on the bactericidal effectiveness of pulsed electric fields (PEF) applied on Listeria innocua suspended in McIllvaine buffer was investigated. Electric field intensity and number of applied pulses were applied in the ranges of 31-40 kV/cm and 5-35 pulses, respectively. Studied treatment temperatures were sustained for 10 s, and ranged between 19°C and 59°C depending on the amount of energy delivered by the PEF treatment. The application of PEF at higher temperatures proved to be more effective than either PEF at low temperatures or the applied thermal treatments by themselves. A maximum bacterial inactivation of 6-log cycles was obtained by applying either: 20 pulses of 40 kV/cm at 65°C, 25 pulses of 36 kV/cm at 61°C, or 31 pulses of 31 kV/cm at 56°C. On the other hand, a thermal treatment of 66°C sustained for 30 s reduced the bacterial population on its own by only 5-log cycles, and the application of 60 pulses of 31 kV/cm at 30°C caused only 3-log cycles of bacterial inactivation. The findings in this study suggest that PEF technology may be effectively used as an enhanced mild thermal preservation method.