Modelling the effect of the redox potential and pH of heating media on<i>Listeria monocytogenes</i>heat resistance

Abstract

AIMS: Study the effect of redox potential and pH of the heating media on Listeria monocytogenes heat resistance and model its action at fixed temperature. METHODS AND RESULTS: The heat resistance of Listeria monocytogenes at 58 degrees C was studied in Brain Heart Infusion broth as a function of pH (from 5.0 to 7.0) and redox potential (E(h7)). The media redox was adjusted with nitrogen gas, potassium ferricyanide and dithiothreitol. A Weibull model was used to fit survival curves. The heat resistance parameter (delta(58 degrees C)) was estimated from each inactivation curve. A major effect of pH was observed. Bigelow model was used to describe the effect of redox potential on the apparent L. monocytogenes heat resistance. The highest delta(58 degrees C) values have been obtained at pH 7.0 and oxidizing conditions. CONCLUSIONS: The developed model indicates that the E(h7) has a significant effect and varied depending on the pH of the heating media. The z(redox) values, calculated from delta(58 degrees C) allowed quantifying the influence of heating media redox potential on L. monocytogenes thermal inactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: The obtained model shows the action of redox potential on L. monocytogenes thermal destruction and might be useful to take into account in food thermal processes.