Development of a log-quadratic model to describe microbial inactivation, illustrated by thermal inactivation of Clostridium botulinum

Stone, G., Chapman, B., & Lovell, D. R. (2009) Development of a log-quadratic model to describe microbial inactivation, illustrated by thermal inactivation of Clostridium botulinum. Applied and Environmental Microbiology, 75(22), pp. 6998-7005.

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In the commercial food industry, demonstration of microbiological safety and thermal process equivalence often involves a mathematical framework that assumes log-linear inactivation kinetics and invokes concepts of decimal reduction time (DT), z values, and accumulated lethality. However, many microbes, particularly spores, exhibit inactivation kinetics that are not log linear. This has led to alternative modeling approaches, such as the biphasic and Weibull models, that relax strong log-linear assumptions. Using a statistical framework, we developed a novel log-quadratic model, which approximates the biphasic and Weibull models and provides additional physiological interpretability. As a statistical linear model, the log-quadratic model is relatively simple to fit and straightforwardly provides confidence intervals for its fitted values. It allows a DT-like value to be derived, even from data that exhibit obvious "tailing." We also showed how existing models of non-log-linear microbial inactivation, such as the Weibull model, can fit into a statistical linear model framework that dramatically simplifies their solution. We applied the log-quadratic model to thermal inactivation data for the spore-forming bacterium Clostridium botulinum and evaluated its merits compared with those of popular previously described approaches. The log-quadratic model was used as the basis of a secondary model that can capture the dependence of microbial inactivation kinetics on temperature. This model, in turn, was linked to models of spore inactivation of Sapru et al. and Rodriguez et al. that posit different physiological states for spores within a population. We believe that the log-quadratic model provides a useful framework in which to test vitalistic and mechanistic hypotheses of inactivation by thermal and other processes. Copyright © 2009, American Society for Microbiology. All Rights Reserved.

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ID Code: 79871
Item Type: Journal Article
Refereed: Yes
Additional Information: Articles free to read on journal website after 6 months
Keywords: Biphasic, Clostridium botulinum, Commercial foods, Confidence interval, Decimal reduction, Fitted values, Inactivation kinetics, Interpretability, Linear model, Mathematical frameworks, Microbial inactivation, Microbiological safety, Modeling approach, Physiological state, Quadratic models, Spore-forming bacteria, Statistical framework, Thermal inactivation, Thermal process, Weibull models, Z value, Bacteria, Physiological models, Thermal logging, bacterium, food safety, microbial activity, numerical model, physiology, reaction kinetics, spore, article, bacterial spore, bacterium contamination, controlled study, disinfection, food contamination, food industry, heat treatment, statistical model, temperature sensitivity, Colony Count, Microbial, Linear Models, Microbial Viability, Models, Biological, Models, Statistical, Spores, Bacterial, Temperature, Time Factors, Bacteria (microorganisms)
DOI: 10.1128/AEM.01067-09
ISSN: 0099-2240
Subjects: Australian and New Zealand Standard Research Classification > BIOLOGICAL SCIENCES (060000)
Australian and New Zealand Standard Research Classification > BIOLOGICAL SCIENCES (060000) > MICROBIOLOGY (060500)
Divisions: Current > Schools > School of Electrical Engineering & Computer Science
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Deposited On: 07 Jan 2015 02:51
Last Modified: 27 Jan 2015 05:28

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