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

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Abstract
Spore germination, growth and survival of C. 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.degree. C at increment rates of 7-25.degree. C/h or to falling temperature from 60-15 or 10.degree. C at decrement rates of 5 to 25.degree. 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.degree. C in the media and in roast beef. During exposure to falling-temperature rates of 25 to 15.degree. C, no change in the population was observed; multiplication of not > 10-fold at 10.degree. C/h and exponential multiplication at 7.5 and 5.degree. C/h were observed. Roast beef prepared with gluteus, semitendinosus, or halved semitendinous 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.