Title: Effect of preincubation temperature and pH on the individual cell lag phase of Listeria monocytogenes, cultured at refrigeration temperatures
Authors: Francois, K ×
Valero, A
Geeraerd, Annemie
Van Impe, Jan
Debevere, J
Garcia-Gimeno, R. M
Zurera, G
Devlieghere, F #
Issue Date: Feb-2007
Publisher: Academic Press
Series Title: Food Microbiology vol:24 issue:1 pages:32-43
Conference: date:Univ Ghent, Dept Food Safety & Food Qual, Lab Food Microbiol & Food Preservat, B-9000 Ghent, Belgium; Katholieke Univ Leuven, Dept Chem Engn, BioTec, B-3001 Louvain, Belgium; Univ Cordoba, Fac Vet, Dept Food Sci & Technol, Cordoba 14104, Spain
Abstract: The impact of precultural temperature and pH on the distribution of the lag phase of individual Listeria monocytogenes cells was assessed during preincubation at 7 degrees C, using a dilution protocol to obtain single cells, and optical density measurements to estimate the individual lag phase. Firstly, the pure temperature effect (37, 15, 10, 7, 4 and 2 degrees C) was investigated on a subsequent growth at 7 degrees C and pH 7.4. Secondly, low precultural temperatures (10, 7 and 4 degrees C) were combined with a controlled pH at 7.4 and 5.7 with a subsequent growth at 7 degrees C and at different pH values (7.4, 6.0 and 5.5). For all temperature-pH combinations, the individual cell lag phase was determined using a three-phase linear growth model. It was observed that at low precultural temperatures (2, 4 and 7 degrees C), a high proportion of L. monocytogenes cells were able to grow at 7 degrees C with almost no lag phase, consequently, the resulting distributions were positively skewed. Beside this, the variability observed was lower than at higher precultural temperatures. Regarding the precultural pH effect, at pH 7.4 the mean values of the lag phases were shorter at lower preincubation temperatures; while at pH 5.7 small pH transitions produced shorter individual lag phases at all precultural temperatures. The quantification of the effect of precultural conditions on the individual cell lag phase duration would improve the accuracy of the existing growth models, especially when a series of processing and storage steps are linked together in a process model or exposure assessment. Distributions will be fitted to the data for every set of conditions, generating useful tools for further risk assessment purposes. (c) 2006 Elsevier Ltd. All rights reserved.
Description: [**]
ISSN: 0740-0020
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division of Mechatronics, Biostatistics and Sensors (MeBioS)
Bio- & Chemical Systems Technology, Reactor Engineering and Safety Section
× corresponding author
# (joint) last author

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