Heat resistance of the chemical resistance forms of Clostridium botulinum 62A spores over the water activity range 0 to 0.9.

Having available the separate chemical resistance forms of Clostridium botulinum 62A spores from an investigation of the effect of spore form on wet heat resistance and also a method for measuring heat resistance at known water activities over the whole water activity (aw) range, we measured the heat resistance of these preparations at four different temperatures at each aw interval of 0.1 from aw 0 to aw 0.9. The required temperature dependence of resistance was calculated for each aw increment. The spore forms showed a low resistance at aw values of 0 and 0.7 of 0.9, with a rise in resistance in the range aw 0.1 to 0.5. The temperature dependence values behaved similarly.