Isothermal inactivation of Salmonella, Listeria monocytogenes, and Enterococcus faecium NRRL B-2354 in peanut butter, powder infant formula, and wheat flour

Pathogens in low water activity foods are an important emerging food safety concern due to notable survival and thermotolerance. Limited but growing data publicly available compare the thermotolerance of Listeria monocytogenes, Salmonella spp., Enterococcus faecium NRRL B-2354 (a surrogate). The aims this study were determine assess bacterial thermal inactivation rates two pathogens a well-established surrogate across three different low-moisture matrices containing levels fat using dry inoculation method. Three (0.11 aw, 45% peanut butter; 0.20 27% powder infant formula; 0.45 < 2% wheat flour) inoculated at room temperature (24.8 °C) with inoculum either E. faecium, spp. cocktail, or L. monocytogenes cocktail. Uniform bagged samples 9 treatments sandwiched copper plates heat-treated via immersion hot bath during isothermal ranging from 60 °C 90 °C. tests conducted triplicate. Bacterial was detected direct plating on tryptic soy agar 0.6% yeast extract. In butter most formula treatments, had significantly higher D-values than comparable temperatures (p 0.05). However, D65°C- D75°C-values between flour D85°C-values undifferentiated. each matrix singular exception observed which not statistically different. effect for bacteria reported descending order as > vast majority D-values. While is primary pathogen outbreaks, these results indicate can exhibit similar thermotolerances low-water including formula.