Clostridium botulinum spore germination, outgrowth, and toxin production below pH 4.6; interactions between pH, total acidity, and buffering capacity

A microbiological study assessed the effect of soy protein concentration on Clostridium botulinum (CB) spore germination, outgrowth, and toxin production in the presence of varying levels of inorganic (HCl) or organic (citric) acids under anaerobic conditions. CB germination, outgrowth, active motility, and toxin formation occurred at acidities as high as pH 4.07. It was concluded that titratable acidity, which accounted for the soy protein buffering capacity, might be more important than pH in defining toxicity endpoints. Acidities of 0.27% (as HCl) and 0.160% (as citric acid) arrested post-germinative CB cell development in acidified soy media to sufficiently restrict toxin production to below mouse bioassay detection levels.(wz)