Germination and outgrowth of Clostridium perfringens spores during chilling of thermally processed ready -to -eat meat products

Spores of foodborne pathogens can survive traditional thermal-processing schedules used in the manufacturing of processed meat products. Heat activated spores can germinate and grow to hazardous levels if these products are improperly chilled. Germination and outgrowth of Clostridium perfringens spores in cured and non-cured ready-to-eat (RTE) meat and poultry products that were cooked and chilled according to commercial processing schedules was studied. Inhibitory effects of organic acid salts on germination and outgrowth of C. perfringens during chilling and survival of vegetative cells and spores during subsequent storage at abusive refrigeration temperatures were evaluated. Ready-to-Eat meat products were formulated to achieve final product concentrations of 1% salt, 0.2% potassium tetrapyrophosphate and 0.2% starch. The products were subsequently ground and mixed with antimicrobials [sodium lactate (SL) and SL plus sodium diacetate (SD), 2.5%; buffered sodium citrate (BSC) and BSC plus SD, 1.3%]. The products were inoculated separately, with a three-strain cocktail of C. perfringens spores, mixed, vacuum packaged, commercially cooked to activate spores and chilled exponentially from 54.5 to 7.2°C in 9, 12, 15, 18, 21 or 24 h. C. perfringens populations (vegetative and spore) were enumerated before and after cooking as well as during chilling and subsequent refrigerated (10°C) storage for up to 60 days. Germination and outgrowth of C. perfringens spores was observed during all cooling scenarios. Addition of antimicrobials prevented outgrowth of C. perfringens spores, while refrigeration at 10°C for 60 days was detrimental to survival of vegetative cells. Germination and outgrowth of C. perfringens spores at isothermal temperature conditions was determined for each inoculated product to develop modeling equations and relative growth rates using the modified Gompertz and Baranyi models for non-linear regression. A modified Ratkowsky equation (square-root) was used to analyze the effect of temperature on relative growth rate. The fourth-order Runge-Kutta numerical method was used to develop final predictive models for each product. Six predictive models were developed to describe germination and outgrowth of C. perfringens in cured and non-cured roast beef, turkey and pork during dynamic cooling. In general, all the models were capable of predicting growth when compared to most validation experiments. These predictive models will allow regulatory agencies as well as meat processors to evaluate product disposition in cases of cooling process deviations. Additionally, these models will allow processors to validate their processing operations with a food safety approach