Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2003
Publication Date: 6/1/2003
Citation: Juneja, V.K., Marks, H.M., Mohr, T. 2003. Predictive thermal inactivation model for salmonella serotypes with temperature, sodium lactate, nac1 and sodium pyrophosphate as controlling factors. Applied and Environmental Microbiology. 69(9):5138-5156. Interpretive Summary: Salmonella is a pathogen of major concern for the food industry due to its association with several outbreaks of foodborne illness. Undercooked meat products are commonly implicated as transmission vehicles in these outbreaks. This emphasizes the need to better define and quantify the heat treatment given to these foods to provide an adequate degree of protection against survival of Salmonella spp. We developed a mathematical model for predicting the destruction of this pathogen in beef. The model can be used to predict the time required at any temperature to kill a certain number of this bacterium. This information will be of immediate use to consumers and to the food industry and regulatory agencies to aid in the development of guidelines to ensure the safety of the food supply.
Technical Abstract: Analyses of survival data of an eight strain cocktail of Salmonella spp. in ground beef with different concentrations of salt, sodium pyrophosphate (SPP), and sodium lactate (NaL) obtained after heating at different temperatures (55, 60, 65, and 71.1°C) indicated that heat resistance of Salmonella increases with increasing levels of SPP, and, depending on temperature, also on increasing levels of salt. The evidence suggested that, in comparison with these two variables, NaL does not significantly affect heat resistance. The magnitude of the SPP effect is predicted to increase with levels of SPP, while the effect of salt is more pronounced for lower temperatures (< 65°C). For example, at 60°C, when increasing the concentration of salt from 0% to 4.5%, the time to reach a 6.5 log10 relative reduction is predicted to increase by about a 2.4 factor (20 min to 47 min when SPP = 0%, and 37 min to 89 min when SPP=0.5%). An omnibus model for predicting the lethality for given times and temperatures in beef was developed that reflects the convex survival curves that were observed. At 71.1°C (160°F), the model predicts that more than 0.5 min may be needed to achieve a 6.5 - log10 relative reduction. The model will be incorporated into the USDA-Pathogen Modeling Program and can be used by food processors in the design of processing times and temperatures that ensure safety against Salmonella serotypes in cooked beef products.