Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-23T07:02:05.887Z Has data issue: false hasContentIssue false
  • English
  • Français

A survey of sources of heat-resistant bacteria in milk with particular reference to psychrotrophic spore-forming bacteria

Published online by Cambridge University Press:  01 June 2009

Charles H. McKinnon  and
Graham L. Pettipher
Charles H. McKinnon
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9 AT, UK
Graham L. Pettipher
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9 AT, UK
Get access Rights & Permissions [Opens in a new window]

Summary

Samples of winter bedding and summer pasture, rinses of teats and milking equipment, and milk samples from bulk tanks from 4 farms were analysed bacteriologically for total count (TC), thermoduric count, total spore count (TSC) and psychrotrophic spore count (PSC).

In bedding and pasture samples the TSC comprised the main component of the thermoduric flora but was less than 0·1 % of the TC. The PSC formed ∼ 1 % of the TSC in winter bedding and ∼23 % of the TSC in pasture. For pasture, the PSC: TSC ratio was highest for the upper layer of soil and lower for the grass and deeper layer of soil. The TSC formed 5% of the thermoduric flora in rinses of milking equipment and only a very low PSC was obtained. The TSC of farm bulk tank milks was higher in the winter than the summer but the PSC was similar in both seasons. This was due to an increase of ∼9 times in the PSC:TSC ratio for milks in summer compared with winter. The PSC in raw and commercially pasteurized milks from a local creamery showed a similar seasonal trend.

Type
Original Articles
Information
Journal of Dairy Research , Volume 50 , Issue 2 , May 1983 , pp. 163 - 170
Copyright
Copyright © Proprietors of Journal of Dairy Research 1983

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

British Standards Institution 1968 Methods of microbiological examinations for dairy purposes. BS no. 4285. London: B.S.I.Google Scholar
Coghill, D. & Juffs, H. S. 1979 Incidence of psychrotrophic sporeforming bacteria in pasteurized milk and cream products and effect of temperature on their growth. Australian Journal of Dairy Technology 34 150–153Google Scholar
Collins, E. B. 1981 Heat resistant psychrotrophic microorganisms. Journal of Dairy Science 64 157–160CrossRefGoogle ScholarPubMed
Franklin, J. G. 1966 Laboratory methods for pasteurising milk. 17th International Dairy Congress, Munich B 515–522Google Scholar
Grosskopf, J. C. & Harper, W. J. 1974 Isolation and identification of psychrotrophic sporeformers in milk. Milchwissenschaft 29 467–470Google Scholar
Johnson, C. 1979 How to get 20-day shelf life in fluid milk. American Dairy Review 41 (7) 24 26 27 46Google Scholar
Johnston, D. W. & Bruce, J. 1982 Incidence of thermoduric psychrotrophs in milk produced in the west of Scotland. Journal of Applied Bacteriology 52 333–337CrossRefGoogle ScholarPubMed
Langeveld, L. P. M., Cuperus, F. & Stadhouders, J. 1973 Bacteriological aspects of the keeping quality at 5 °C of reinfected and non-reinfected pasteurized milk. Netherlands Milk and Dairy Journal 27 54–65Google Scholar
McKinnon, C. H. & Cousins, C. M. 1969 Automatic spray cleaning of bulk tanks: the results of a field trial. Journal of the Society of Dairy Technology 22 227–232CrossRefGoogle Scholar
McLarty, R. M. 1981 In Disinfectants: their use and evaluation of effectiveness pp. 171–176 (Ed. Collins, C. H. et al.) London: Academic PressGoogle Scholar
Schröder, M. J. A., Cousins, C. M. & Mckinnon, C. H. 1982 Effect of psychrotrophic post-pasteurization contamination on the keeping quality at 11 and 5 °C of HTST-pasteurized milk in the UK. Journal of Dairy Research 49 619–630CrossRefGoogle ScholarPubMed
Sharps, A. N. & Jackson, A. K. 1972 Stomaching: a new concept in bacteriological sample preparation. Applied and Environmental Microbiology 24 175–178CrossRefGoogle Scholar
Underwood, H. M., McKinnon, C. H., Davies, F. L. & Cousins, C. M. 1974 Sources of bacillus spores in raw milk. 19th International Dairy Congress, New Delhi 1E 373–374Google Scholar
Washam, C. J., Olson, H. C. & Vedamuthu, E. R. 1977 Heat-resistant psychrotrophic bacteria isolated from pasteurized milk. Journal of Food Protection 40 101–108CrossRefGoogle ScholarPubMed