Growth and Sporulation Potential of Clostridium perfringens in Aerobic and Vacuum-Packaged Cooked Beef

Abstract

Growth of Clostridium perfringens in aerobic-and anaerobic-(vacuum) packaged cooked ground beef was investigated. Autoclaved ground beef was inoculated with ~3.0-log10 CFU/g of C. perfringens, packaged and stored at various temperatures. Vegetative cells and heat-resistant spores were enumerated by plating unheated and heated (75°C for 20 min) meat samples on tryptose-sulfite-cycloserine agar. Clostridium perfringens grew to >7 logs within 12 h at 28, 37 and 42°C under anaerobic atmosphere and at 37 and 42°C under aerobic conditions. At 28°C under aerobic conditions, growth was relatively slow and total viable count increased to >6 logs within 36 h. Similarly, growth at 15°C in air was both slower and less than under vacuum. Regardless of packaging, the organism either declined or did not grow at 4, 8 and 12°C. Spores were not found at <12°C. Spores were detected as early as 8 h at 42°C under anaerobic conditions, but in general, the type of atmosphere had little influence on sporulation at ≥28°C. Temperature abuse (28°C storage) of refrigerated products for 6 h will not permit C. perfringens growth. However, cyclic and static temperature abuse of such products for relatively long periods may lead to high and dangerous numbers of organisms. Reheating such products to an internal temperature of 65°C before consumption would prevent food poisoning since the vegetative cells were killed.