Mathematical modelling of the heat resistance of Listeria monocytogenes |
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Authors: | Augustin,Carlier,& Rozier |
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Affiliation: | Service d'Hygiène et Industrie des Denrées Animales et d'Origine Animale, Ecole Nationale Vétérinaire d'Alfort, Maisons Alfort, Cedex, France |
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Abstract: | The heat resistance of Listeria monocytogenes phagovar 2389/2425/3274/2671/47/108/340 (1992 French outbreak strain) in broth was studied at 55, 60 and 65 °C. Experiments were carried out on bacterial cultures in three different physiological states: cultures at the end of the log phase, cultures heat-shocked at 42 °C for 1 h, and subcultures of cells resistant to prolonged heating. Survivor curves were better fitted using a sigmoidal equation than the classical log-linear model. This approach was justified by the existence of heat resistance distributions within the bacterial populations. Peaks (log10 of heating time) of heat resistance distributions of untreated, heat-shocked, and selected cultures at 55, 60 and 65 °C were 0·34, −0·90 and −1·84 min, 0·74, −0·51 and −1·24 min, and 0·17, −0·94 and−1·45 min, respectively. The widths of the distributions are proportional to 0·29, 0·36and 0·41 min0·5, 0·26, 0·36 and 0·41 min0·5, and 0·34, 0·44 and 0·41 min0·5. An increase in thethermal tolerance could then be induced by sublethal heat shock or by selection of heatresistant cells. |
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