title: Quantifying variability on thermal resistance of Listeria monocytogenes.
abstract: Knowledge of the impact of strain variability and growth history on thermal resistance is needed to provide a realistic prediction and an adequate design of thermal treatments. In the present study, apart from quantifying strain variability on thermal resistance of Listeria monocytogenes, also biological variability and experimental variability were determined to prioritize their importance. Experimental variability was defined as the repeatability of parallel experimental replicates and biological variability was defined as the reproducibility of biologically independent reproductions. Furthermore, the effect of growth history was quantified. The thermal inactivation curves of 20 L. monocytogenes strains were fitted using the modified Weibull model, resulting in total 360 D-value estimates. The D-value ranged from 9 to 30 min at 55 °C; from 0.6 to 4 min at 60 °C; and from 0.08 to 0.6 min at 65 °C. The estimated z-values of all strains ranged from 4.4 to 5.7 °C. The strain variability was ten times higher than the experimental variability and four times higher than the biological variability. Furthermore, the effect of growth history on thermal resistance variability was not significantly different from that of strain variability and was mainly determined by the growth phase.
authors.affiliation: Top Institute Food and Nutrition, Nieuwe Kanaal 9A, 6709 PA Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: D C
authors.initials: DC
authors.lastname: Aryani
authors.affiliation: Top Institute Food and Nutrition, Nieuwe Kanaal 9A, 6709 PA Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: heidy.denbesten@wur.nl.
authors.forename: H M W
authors.initials: HM
authors.lastname: den Besten
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: W C
authors.initials: WC
authors.lastname: Hazeleger
authors.affiliation: Top Institute Food and Nutrition, Nieuwe Kanaal 9A, 6709 PA Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: M H
authors.initials: MH
authors.lastname: Zwietering
mesh_terms: D005516:Food Microbiology; D006358:Hot Temperature; D008089:Listeria monocytogenes / Q000254:growth & development / Q000502:physiology*; D050296:Microbial Viability; D008962:Models, Theoretical; D015203:Reproducibility of Results; D013045:Species Specificity
keywords: D-value; Heterogeneity; Modified Weibull model