Abstract
Clostridium botulinum type A spores were inoculated at a level of 10(7) spores per ml into sterile beef media with protein concentrations of 1, 2, 3, 4, or 6% and acidified to pH values of 2.01 to 4.75 with hydrochloric acid or 4.19 to 4.60 with citric acid. All experimental manipulations, including blending, acidification, inoculation, incubation (30 degrees C), and analyses, were conducted in an anaerobic chamber-incubator in which atmospheric oxygen levels were maintained below 2 ppm (2 microliters/liter). Under these strict anaerobic conditions (oxidation-reduction values in media ranging from -370 to -391 mV), C. botulinum spores were consistently found to germinate, grow, and produce toxin below pH 4.6. The boundary between toxic and atoxic samples in HC1-acidified beef media was mediated by titratable acidity, pH, and protein concentration. A limiting acidity was not established for the citrate-acidified samples; all blends tested (1, 2, 3, and 4% protein and titratable acidities of 0.091 to 0.453%) became toxic within 5 weeks. At the same pH and protein concentration, citric acid was less effective than HC1 in preventing the germination of C. botulinum spores. Higher levels of cell proliferation in the beef protein, as well as enhanced gas production and putrefactive degradation, indicated that beef was a better substrate than soy for C. botulinum spores under these conditions. Reducing the inoculum to 10(4) delayed but did not prevent spore outgrowth and toxin release at pH levels below 4.6.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Baird-Parker A. C., Freame B. Combined effect of water activity, pH and temperature on the growth of Clostridium botulinum from spore and vegetative cell inocula. J Appl Bacteriol. 1967 Dec;30(3):420–429. doi: 10.1111/j.1365-2672.1967.tb00320.x. [DOI] [PubMed] [Google Scholar]
- Graham A. F., Lund B. M. The effect of citric acid on growth of proteolytic strains of Clostridium botulinum. J Appl Bacteriol. 1986 Jul;61(1):39–49. doi: 10.1111/j.1365-2672.1986.tb03756.x. [DOI] [PubMed] [Google Scholar]
- Huhtanen C. N., Naghski J., Custer C. S., Russell R. W. Growth and toxin production by Clostridium botulinum in moldy tomato juice. Appl Environ Microbiol. 1976 Nov;32(5):711–715. doi: 10.1128/aem.32.5.711-715.1976. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mead G. C. The amino acid-fermenting clostridia. J Gen Microbiol. 1971 Jul;67(1):47–56. doi: 10.1099/00221287-67-1-47. [DOI] [PubMed] [Google Scholar]
- Odlaug T. E., Pflug I. J. Clostridium botulinum growth and toxin production in tomato juice containing Aspergillus gracilis. Appl Environ Microbiol. 1979 Mar;37(3):496–504. doi: 10.1128/aem.37.3.496-504.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raatjes G. J., Smelt J. P. Clostridium botulinum can grow and form toxin at pH values lower than 4.6. Nature. 1979 Oct 4;281(5730):398–399. doi: 10.1038/281398a0. [DOI] [PubMed] [Google Scholar]
- Smelt J. P., Raatjes G. J., Crowther J. S., Verrips C. T. Growth and toxin formation by Clostridium botulinum at low pH values. J Appl Bacteriol. 1982 Feb;52(1):75–82. doi: 10.1111/j.1365-2672.1982.tb04375.x. [DOI] [PubMed] [Google Scholar]