Modelling the effect of the redox potential and pH of heating media on Listeria monocytogenes 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°C was studied in Brain Heart Infusion broth as a function of pH (from 5-0 to 7-0) and redox potential (Eh7). 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 (δ58°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 δ58°C values have been obtained at pH 7-0 and oxidizing conditions. Conclusions: The developed model indicates that the Eh7 has a significant effect and varied depending on the pH of the heating media. The zredox values, calculated from δ58°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.