Growth and survival of Yersinia enterocolitica, Salmonella and Bacillus cereus in Brie stored at 4, 8 and 20°C

Abstract The potential of stabilised Brie to support growth of the food-borne pathogens, Yersinia enterocolitica serotypes 0:3 and 0:9, Salmonella typhimurium, S. dublin (both dairy isolates), S. thompson , and Bacillus cereus (3 dairy isolates), after contamination on opening the cheese package was evaluated. Growth kinetics of the different pathogens was determined in relation to inoculum size and storage temperature (4°C, 8°C and 20°C). Only Y. enterocolitica was found to grow on the surfaces (outer and exposed) of Brie at all three storage temperatures. Growth of this pathogen during refrigerated storage must be avoided to ensure safety. The numbers of B. cereus and Salmonella increased at 20°C but declined at a slow rate during storage at 4°C and 8°C. However, survival of these two pathogens for extended periods at abuse temperatures could pose a health hazard. Predictions from a predictive modelling program (MFS model) and a modelling database (Food Micromodel) were compared to observed growth values in Brie. Although accurate in the case of B. cereus at 20°C, predicted generation times were in general found to be considerably shorter than the observed values, i.e., overall they were ‘fail safe’. Predicted lag times, however, were generally longer compared to observed values in the case of Y. enterocolitica and at low inocula for Salmonella , and would ‘fail dangerous’ if used for predictive purposes.