Growth pH does not affect the initial physiological state parameter (p0) of Listeria monocytogenes

被引:13
作者
McKellar, RC [1 ]
Lu, X [1 ]
Knight, KP [1 ]
机构
[1] Agr & Agri Food Canada, Food Res Program, Guelph, ON N1G 5C9, Canada
关键词
mathematical model; predictive microbiology; lag phase; growth; Listeria monocytogenes; physiological state; pH;
D O I
10.1016/S0168-1605(01)00644-4
中图分类号
TS2 [食品工业];
学科分类号
0832 ;
摘要
It has proven difficult to develop adequate mathematical models for the lag phase (lambda) which characterizes the adaptation period prior to the initiation of exponential growth by microorganisms. This is due, in part, to our incomplete understanding of the nature of the initial physiological state of cells (defined as h(0) or p(0) depending on the model), and changes taking place during adaptation. The objectives of the present study were to characterize p(0) using data from growth of Listeria monocytogenes in an automated turbidimetric instrument (Bioscreen), and to determine the influence of limiting growth pH. A model was developed for individual cells which combined a continuous adaptation phase (defined by p(0)) with a discrete step marking the transition to a continuous exponential growth phase (the CDC model). Parameters of the new model were: p(0); the specific growth rate (mu); the initial cell number (N-0); and the maximum cell density (N-max). Progressive reduction of the growth pH in the Bioscreen to 4.7 decreased the mu. It was noted that the regression lines for all trials at all pH values appeared to have a common x-intercept (20.086 +/- 1.092), and it was deduced that, when the Bioscreen detection limit (15.07 In cfu well (-1)) was subtracted, the resulting value represented the "true" value for the initial physiological state of the cells. (C) 2002 Elsevier Science B.V All rights reserved.
引用
收藏
页码:137 / 144
页数:8
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