Modelling of microbial non-linear
thermal inactivation kinetics: a review

Gain insight into the significance and modelling of non-linear death kinetics of food micro-organisms, and how this relates to the traditional use of D and z models

The D model of micro-organism death has served the food industry well for many years. The concept of 'D' as a 'decimal reduction time' has been easy to understand and apply. The 'z-value' concept has been a standard and consistent extension of this, being the change in conditions needed for a decimal change in the decimal reduction time. Further elaboration, such as 'F' values, has provided a foundation for the assessment and control of processes. The successful application of these principles provides eloquent testimony to their validity and suitability in their traditional areas of application.

However, with the food industry constantly modifying and developing processes and products, it is important that the limits of the 'D' model are understood and that alternatives are available as supplements, for use in special circumstances. This review provides an up-to-date discussion of the alternative approaches that have been considered and the types of circumstances under which these might apply. It includes, as an appendix, a complete copy of CCFRA's 1992 review of alternatives to the D and z value, to which it refers extensively.

Contents:

• Introduction

• Bacteria, substrates and treatments
• Modelling approaches

• Models

• D model
• Log-normal distribution (Probit)
• Log-Logistic model
• Weibull distribution model
• Gompertz equation
• Baranyi model
• Comparative papers

• Conclusions
• References
• Appendix - Practical and theoretical aspects of the death kinetics of micro-organisms: alternatives to the D and z concept (CCFRA Technical Bulletin No. 92 - 1992)