Heat resistance of Clostridium perfringens vegetative cells as affected by prior heat shock

This study quantified the heat resistance and the effects of a heat shock on the subsequent heat resistance of 10 strains of Clostridium perfringens. Beef gravy samples inoculated with vegetative cells of the pathogen were subjected to sublethal heating at 48C for 10 min, and then heated to a final temperature of 58C using a submerged-coil heating apparatus. Heat-treated samples were spiral plated on Shahidi-Ferguson Perfringens agar to determine surviving bacterial population. No correlation between the heat resistance and the origin of the C. perfringens could be established due to significant variations in the hear resistance among strains. inactivation kinetics of both heat-shocked and nonheat-shocked samples exhibited log-linear decline in the number of surviving cells with time. D-values at 58C for C. perfringens vegetative cells ranged from 1.21 to 1.60 min. Heat shocking allowed the organism to survive longer and the increase in heat resistance tvas as high as 1.5 fold. Also, heat shock resulted in the overexpression of proteins exhibiting epitopic and size similarity to E. coli GroEL and B. subtilis small acid soluble proteins. Increased heat resistance due to heat shock must be considered while designing cooking/reheating regimes that ensure safety of ready-to-eat foods contaminated with high numbers of C. perfringens vegetative cells.