Effect of sporulation temperature on the resistance of Clostridium botulinum type A spores to thermal and high pressure processing

The purpose of this study was to determine the effect of sporulation temperature on the resistance of Clostridium botulinum type A spores of strains 62A and GiorgioA to thermal and high pressure processing (HPP). Spore crops produced in Trypticase-peptone-glucose-yeast extract broth at four incubation temperatures (20, 27, 37, and 41°C) were harvested, and heat resistance studies were conducted at 105°C (strain 62A) and 100°C (strain GiorgioA). Resistance to HPP was evaluated by subjecting the spores to a high pressure (700 MPa) and temperature combination (105°C, strain 62A; 100°C strain GiorgioA) in a laboratory-scale pressure test system. The decimal reduction time (D-value) was calculated using the log-linear model. Although the time to sporulation for GiorgioA was shorter and resulted in higher spore concentrations than for 62A at 20, 27, and 37°C, GiorgioA did not produce a sufficient spore crop at 41°C to be evaluated. The heat resistance of 62A spores was greatest when produced at 27°C and decreased for spore crops produced above or below 27°C (D105°C-values: 20°C, 1.9 min; 27°C, 4.03 min; 37°C, 3.66 min; and 41°C, 3.5 min; P < 0.05). Unlike 62A, the heat resistance behavior of GiorgioA spores increased with rising sporulation temperature, and spores formed at the organism's optimum growth temperature of 37°C were the most resistant (D100°C-values: 20°C, 3.4 min; 27°C, 5.08 min; and 37°C, 5.65 min; P < 0.05). Overall, all spore crops were less resistant to pressure-assisted thermal processing than thermal treatment alone. Sporulation temperature has an effect on the resistance of C. botulinum spores to heat and HPP, and is characteristic to a particular strain. Knowledge of the effect of sporulation temperature on the resistance of C. botulinum spores is vital for the production of spores utilized in thermal and high pressure inactivation studies.