Potential for Growth of Clostridium perfringens from Spores in Pork Scrapple During Cooling

We conducted stabilization studies to determine the ability of Clostridium perfringens spores to germinate and grow during exponential cooling of a commercial formulation of pork scrapple. Scrapple was inoculated with a mixture of three strains of C. perfringens spores (NTCC 8238, NCTC 8239, and ATCC 10288), vacuum packaged, and reheated (20min/93.3°C) in a circulating water bath. The cooked samples were cooled (30s) in an ice bath before being transferred to a programmable water bath to cool through the temperature range of 54.4°C to 7.2°C in 12, 14, or 21h to simulate deviations from the required cooling time of 6.5h. After cooling, the samples, in duplicate, were analyzed to determine if growth from spores had occurred. The samples were plated onto tryptose-sulfite-cycloserine agar and incubated anaerobically at 37°C for 48h before counting the colonies. Minimal growth (less than 1.0 log) was observed during a 12- or 14h cooling period. However, when the time to achieve 7.2°C was extended to 21h, C. perfringens spores germinated and grew from an inoculum of 3.0 log10 to approximately 7.8 log10 CFU/g. Thus, scrapple must be cooled after cooking to 7.2°C within 6.5h, but for no more than 14h, to prevent a food safety hazard from outgrowth of C. perfringens spores during cooling.