A model for the thermal inactivation of micro-organisms

To mathematically model published thermal inactivation data sets using an empirical model based on a double Arrhenius function.

A mathematical model, the log R-fat, provided an excellent description of the data sets available: the thermal inactivation of Salmonella anatum at 55 degrees C, Pseudomonas viscosa at 48 degrees C and Streptococcus faecalis at 60 degrees C; Clostridium botulinum spores at various temperatures in the range of 101-121 degrees C (two data sets); thermal inactivation of Salmonella Bedford over the temperature range 50-58 degrees C, water activity range of 0.94-0.99 and a pH range of 4-7; Bacillus stearothermophilus spores from 105 to 121 degrees C and the dry heat sterilization of an indigenous mesophilic soil population over the temperature range of 120-160 degrees C.

The log R-fat model, derived from previously published chemical inactivation studies provides as good, if not better, description of thermal inactivation kinetics as other published models. The model does not invoke either of the two hypotheses of inactivation: the mechanistic or vitalistic, although it is closely linked to descriptions of the former.

The log R-fat double Arrhenius function provides the investigator with a relatively simple and easy mathematical model to apply to data of thermal inactivation. This model may allow a more accurate description of thermal food processing, especially when the safety of marginal heat processes are concerned.