Track advances in microbial modeling.

The use of heat to inactivate foodborne pathogens is a critical control point and the most common means of assuring the microbiological safety of processed foods.

A key to optimizing the heating step is to define the target pathogen's heat resistance. Sufficient evidence exists to document that insufficient cooking, reheating or any subsequent cooling may often be factors that contribute to food-poisoning outbreaks. So, USDA-ARS researchers set out to determine the heat treatment required to achieve a specific lethality for foodborne pathogens, and the safe cooling rate for cooked meat. They developed computer models that should aid in evaluating the safety of cooked products and which could be used as building blocks for microbial risk assessment.

When attempting to assess the heat inactivation kinetics of E. coli O157:H7, L. monocytogenes, Salmonella and spores of non-proteolytic C. botulinum, the scientists took into account a number of variables, including the effects and interactions of temperature, pH, sodium chloride content, sodium pyrophosphate and sodium lactate concentration. Incorporating these different barriers increased the sensitivity of the pathogens to heat. This in turn reduced the heating requirements and ensured the safety of ready-to-eat products.

The investigators developed models that predict growth from surviving spores of C. perfringens and proteolytic C. botulinum at temperatures applicable to the cooling of cooked meat. Predictive inactivation kinetics of thermal death and cooling deviation models for foodborne pathogens have been converted into an easy-to-use computer program that is available at http://ars.usda.gov/services/docs.htm?docid=6786.

This Pathogen Modeling Program is a package of models that can be used to predict the growth and inactivation of foodborne bacteria, primarily pathogens, under various environmental conditions. These predictions are specific to certain bacterial strains and specific environments, e.g., culture media and food, used in generating the models.

Further information. Vijay K. Juneja, USDA-ARS Eastern Regional Research Center, Microbial Food Safety Research Unit, Room 2129.3, 600 E. Mermaid Lane, Wyndmoor, PA 19038; phone: 215-233-6500; fax: 215-233-6581; email: vijay.juneja@ars.usda.gov.

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