Predicting pathogen growth and death in raw meat and poultry: Challenge studies and predictive tools

Since 2000, all wholesale meat and poultry processors have had the mandatory Hazard Analysis Critical Control Point (HACCP) system in place. An important part of the HACCP system is the use of scientifically validated information to set critical limits at Critical Control Points that control hazards identified by the processor. In this work we provide scientifically valid information by developing predictive tools and conducting industry-specific challenge studies. Our efforts were focused on corrective actions after raw-product temperature abuse, evaluating critical limits for slow-cooking processes, and evaluating lethality of low-temperature processing of ready-to-eat meats. We developed a predictive tool based on lag phase duration and growth rate values obtained under isothermal growth conditions for Escherichia coli O157: H7, Salmonella serovars, and Staphylococcus aureus in ground beef, ground pork, and ground poultry. This tool, THERM (Temperature History Evaluation of Raw Meats), uses an interval accumulation method to predict pathogen behavior in static or dynamic temperature systems. We tested the accuracy of THERM predictions using several temperature-abuse challenge studies with coarse-ground beef and poultry products. Using a qualitative (growth vs. no growth) standard for evaluating pathogen behavior, THERM accurately predicted growth of E. coli O157:H7, Salmonella serovars, and S. aureus in 67, 85, and 95% of experiments and was fail-safe (predicted growth but no growth was observed) in the remaining experiments. THERM also performed well in qualitatively predicting pathogen growth during slow-cooking of beef roasts and ham. Several low-temperature process challenge studies were conducted on products outside the scope of THERM. Results were variable and producers making low-temperature ready-to-eat products may not be able to validate the safety of these processes without significant product formulation or process changes. In certain raw-meat processing deviations, it is possible that E. coli O157:H7 or Salmonella serovars grow but S. aureus either does not grow at all or does not grow enough to produce dangerous amounts of heat stable enterotoxin. A probabilistic tool, CHAMP (Calculating Heat-lethality Associated with Meat Processing), was designed, but did not provide conclusive results in predicting whether augmented thermal processing after such deviations would ensure product safety.