U.S. Department of Agriculture Dairy Processing and Products Research Unit, Eastern Regional Research Center, Agricultural Research Service Wyndmoor USA PA 19038 600 E. Mermaid Lane Wyndmoor USA PA 19038 600 E. Mermaid Lane
scanning calorimetry (DSC) is applicable to studying the thermal properties
of bacteria when treated with heat, cold, or antibiotics. Foodborne pathogens
are inactivated by heat, and denaturation transitions observed by DSC indicate
potential sites of cellular injury. Ribosomes, which are the sites for messenger
RNA translation, are one critical component of thermal damage as evidenced
by characteristic denaturation transitions in the 66-74C range.
These transitions disappear when cells of Clostridium
perfringens are subjected to heat, suggesting structural or conformational
changes to ribosomal proteins, and when cells of Listeria
monocytogenes are cold-shocked by refrigeration, indicating ribosomal
dissociation. DSC can be used to show that refrigeration followed by heat
treatment improves the killing of dangerous microorganisms.