Influence of heating and cooling rates on spore germination and growth of Clostridium perfringens in media and in roast beef.

Abstract

Spore germination, growth and survival of Clostridium perfringens during heating and/or cooling were examined. The spores in media (FTM or ground beef) were exposed to rising temperature from 20 to 60°C at increment rates of 7-25°C/h or to falling temperature from 60 to 15 or 10°C at decrement rates of 5 to 25°C/h. Roast beef was prepared with various muscles inoculated with the spores. Although germination and growth occurred while heating, the vegetative cells were killed at 60°C in media and in roast beef. During exposure to falling-temperature rates of 25 to 15°C, no change in the population was observed; multiplication of not more than 10-fold at 10°C/h and exponential multiplication at 7.5 and 5°C/h were observed. Roast beef prepared with gluteus, semitendinosus, or halved semitendinosus muscle did not support any growth of C.perfringens during cooling/chilling. That prepared with the whole muscles of semimembranosus supported some growth, but it did not surpass the inoculum size.