Relationship of sporulation, enterotoxin formation, and spoilage during growth of Clostridium perfringens type A in cooked chicken

Abstract

Sporulation and enterotoxin formation were determined for 17 strains of C. perfringens type A in autoclaved chicken dark meat and in Duncan-Strong sporulation medium. The mean numbers of heat-resistant spores detected after 24 h at 37°C were log10 1.13 to log10 7.64ml in Duncan-Strong medium and log10 4.93 to log10 6.59/g in chicken. Of 17 strains, 7 formed enterotoxin in Duncan-Strong culture supernatant (1.0 to 60 μg/ml) and 8 produced enterotoxin in chicken (0.21 to 24 μg/g). Additional studies with chicken were conducted with C. perfringens NCTC8239. With an inoculum of 106 cells per g, >log10 7.99 vegetative cells per g were detected by 4h in chicken at 37°C. Heat-resistant spores occurred by 4 and 6 h and enterotoxin occurred by 8 and 6 h in autoclaved chicken dark meat and barbecued chicken drumsticks, respectively. Enterotoxin was detected in autoclaved dark meat after incubation at 45 °C for 1.5 h followed by 37 °C for 4.5 h, but not after incubation at 45° C for 1.5 to 8 h. With an inoculum of 102 cells per g in oven-cooked or autoclaved chicken, >log10 8.00 vegetative cells per g were detected by 6 to 8 h at 37 °C, heat-resistant spores were detected by 8 h, and enterotoxin was detected by 12 h. A statistical analysis of odor determinations of chicken after growth of C. perfringens indicated that, at the 95% confidence level, the product was considered spoiled (off or unwholesome odor) by the time spores or enterotoxin were formed.