Abstract
Thermal inactivation of Clostridium botulinum type A and B toxins produced in various food samples was determined by the time-to-death method by iv injection into mice. Factors influencing the heat stability of the toxin were further examined. Generally, botulinum toxin produced in vegetables was stable as compared with that in meat. Type B (strain Okra) toxin produced in string beans was especially resistant and the activity was detected even after heating at 80°C for 30min. Heating at 90°C for 10min was necessary for complete inactivation. Its high stability was not shown in the supernatant fluid which did not cotnin the particle of string beans and botulinal cells. By heating purified toxin in some menstrua, string beans extract was protective against heat to some extent. The protection afforded by reduced pH was more prominent for type A toxin than type B toxin. No significant difference was seen in the stability of L toxin (16S) and M toxin (12S).
