Describe how spores germinate and make improperly cooled food unsafe.

Safe cooling requires removing heat from food quickly enough to prevent microbial growth. Excessive time for cooling of potentially hazardous foods has been consistently identified as one of the leading contributing factors to foodborne illness. During slow cooling, potentially hazardous foods are subject to the growth of a variety of pathogenic microorganisms. A longer time near ideal bacterial incubation temperatures, 70°F-125°F, is to be avoided. If the food is not cooled properly, pathogens may grow to sufficient numbers to cause foodborne illness.

If the cooking step prior to cooling is adequate and no recontamination occurs, all but the spore-forming microorganisms such as Clostridium perfringens or Bacillus cereus should be killed or inactivated. However, under substandard sanitary conditions, other pathogens such as Salmonella or Listeria monocytogenes may be reintroduced. Thus, cooling requirements are based on the growth characteristics of specific microorganisms that may survive or be post-cooking contaminants that grow rapidly under temperature abuse conditions.

The processing of most ready-to-eat products includes a heat treatment or cooking step to eliminate pathogenic and spoilage microorganisms. However, this heat treatment does not eliminate spores of Clostridium botulinum and Clostridium perfringens and other spore-forming bacteria. Furthermore, these microorganisms can thrive in the warm product since other competing microorganisms have been eliminated. Non-refrigerated, anaerobic conditions are conducive to their growth and multiplication.

To prevent the growth and multiplication of spore-forming microorganisms, product should be cooled rapidly after cooking. When there is inadequate cooling, spores can germinate and the resulting vegetative cells can multiply to hazardous levels. The presence of sufficient numbers of C. botulinum or other spore-forming microorganisms may lead to production of harmful toxins. Therefore, ensuring no growth of these microorganisms will provide the greatest amount of safety.