Abstract
The heat resistance of Bacillus subtilis var. niger has been measured from 85 to 125 degrees C using moisture levels of percent relative humidity (%RH) less than or equal to 0.001 to 100 in a closed system. Five curves have been presented to characterize the thermal destruction, using thermal death times defined as F values at a given combination of three moisture and temperature conditions. Reductions of 99.99% (4-log10 cycles) of the initial population were estimated for the three moisture conditions. At 110 degrees C, the expected time for a 4-log10 reduction was 1.1 h at %RH = 100, 3.1 h at %RH less than or equal to 0.1 and 54 h at %RH = 10.7. Goodness-of-fit tests to examine the adequacy of three polynomial models failed to indicate a trend. The linear model (from which estimates of D are obtained) was satisfactory for estimating the thermal death times (%RH less than or equal to 0.1) in the plate count range. The estimates based on observed thermal death times and D values for the %RH = 100 diverged so that D values generally gave a more conservative estimate over the temperature range 90 to 125 degrees C. Estimates of ZF and ZL ranged from 32.1 to 58.3 degrees C for the %RH less than or equal to 0.1 and 100. A ZD value of 30.0 was obtained for data observed at %RH less than or equal to 0.1. The ZF results were obtained from plotting observed log times to achieve a 99.99% reduction in the initial population versus temperature. Estimates of ZL and ZD were obtained by using linear estimates of L100 approximately equal to 4D and D values in a similar plot.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Angelotti R., Maryanski J. H., Butler T. F., Peeler J. T., Campbell J. E. Influence of spore moisture content on the dry-heat resistance of Bacillus subtilis var. niger. Appl Microbiol. 1968 May;16(5):735–745. doi: 10.1128/am.16.5.735-745.1968. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Murrell W. G., Scott W. J. The heat resistance of bacterial spores at various water activities. J Gen Microbiol. 1966 Jun;43(3):411–425. doi: 10.1099/00221287-43-3-411. [DOI] [PubMed] [Google Scholar]
- Paik W. W., Sherry E. J., Stern J. A. Thermal death of Bacillus subtilis var. niger spores on selected lander capsule surfaces. Appl Microbiol. 1969 Nov;18(5):901–905. doi: 10.1128/am.18.5.901-905.1969. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Puleo J. R., Oxborrow G. S., Fields N. D., Hall H. E. Quantitative and qualitative microbiological profiles of the Apollo 10 and 11 spacecraft. Appl Microbiol. 1970 Sep;20(3):384–389. doi: 10.1128/am.20.3.384-389.1970. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SHORTLEY G., WILKINS J. R. INDEPENDENT-ACTION AND BIRTH-DEATH MODELS IN EXPERIMENTAL MICROBIOLOGY. Bacteriol Rev. 1965 Mar;29:102–141. doi: 10.1128/br.29.1.102-141.1965. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Simko G. J., Devlin J. D., Wardle M. D. Dry-heat resistance of Bacillus subtilis var. niger spores on mated surfaces. Appl Microbiol. 1971 Oct;22(4):491–495. doi: 10.1128/am.22.4.491-495.1971. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wardle M. D., Brewer W. A., Peterson M. L. Dry-heat resistance of bacterial spores recovered from mariner-Mars 1969 spacecraft. Appl Microbiol. 1971 May;21(5):827–831. doi: 10.1128/am.21.5.827-831.1971. [DOI] [PMC free article] [PubMed] [Google Scholar]