Growth and toxin formation by Clostridium botulinum at low pH values

Abstract

Spores of Clostridium botulinum were found to initiate growth and to produce toxin in aqueous suspensions of soya protein at pH values as low as 4‐2 and in skimmed milk at pH 4.4. Most of the experiments were done with mixed cultures of CI. botulinum types A and B in the presence of two strains of Bacillus subtilis. The role of the latter organism was concluded to be to lower the oxygen content and the Eh of the suspensions. Toxin was produced at pH 4‐4 after 4 weeks of incubation at 30oC when either hydrochloric or citric acids were used as the acidulant and after 12 and 14 weeks when, respectively, lactic and acetic acids were used. Thus, amongst other factors the nature of the acid and not solely the pH value is an important factor in controlling the growth of Cl. botulinum at low pH. Pure cultures of Cl botulinum type A grew at 30oC under strictly anaerobic conditions and produced toxin at pH 4‐3 in the presence of hydrochloric acid.

Analysis and mathematical modelling of the behaviour of Escherichia coli in the mascarpone cheese during cold storage

“…In terms of pH value, the mascarpone cheese can be recognised as a medium that is favourable for microbiological growth. In general, the pathogens do not grow, or grow very slowly, at pH levels below 4.6 (Smelt et al ., ).…”

Survival of Bacillus cereus spores and vegetative cells in acid media simulating human stomach

“…Waterman and Small (1998) showed the survival on beef particles of acid‐sensitive bacteria such as Salmonella typhimurium , Shigella flexneri and Escherichia coli and suggested that ground beef could raise the pH of the acidified medium in the microenvironment of the bacteria. Growth of, and toxin production by, Clostridium botulinum at pH 4·3 required proteins from skimmed milk or soya (Smelt et al. 1982).…”

Food stability determination by macro–micro region concept in the state diagram and by defining a critical temperature

“…For example, acetic acid is recognized as a better inhibitor (at similar pH) of bacterial growth than other acids used in food preservation. The minimum pH required to inhibit growth and toxin production by Clostridium botulinum depends on the acid used (Minor and Marth, 1972;Smelt et al, 1982). Similarly Sorrels et al (1989) reported that overall antimicrobial action (i.e.…”