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Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization. II. The sporicidal efficiency of an experimental plant for direct and indirect processing

Published online by Cambridge University Press:  01 June 2009

J. G. Franklin ,
H. M. Underwood ,
A. G. Perkin  and
H. Burton
J. G. Franklin
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
H. M. Underwood
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
A. G. Perkin
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
H. Burton
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
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Summary

The variation of sporicidal efficiency with processing temperature was determined for an experimental ultra-high-temperature (UHT) milk sterilizer operating alternatively as an indirect or as a direct heater. Whole milk was inoculated with large numbers of spores of Bacillus subtilis 786 and Bacillus stearothermophilus TH24, and the proportion of spores surviving the sterilizing process was calculated from dilution and colony counts on the untreated and treated milk. The results for B. subtilis spores were unreliable, and the dilution count results for B. stearothermophilus spores were influenced by the inhibitory effect of the UHT processed milk. The results for the colony counts of B. stearothermophilus spores were preferred as a basis for the comparison of the direct and indirect processes. Over the range of processing temperatures 137–145 °C it was found that the sterilizing temperature had to be 3–4 degC higher with direct heating than with indirect heating to give equal spore destructions.

Type
Original Articles
Information
Journal of Dairy Research , Volume 37 , Issue 2 , June 1970 , pp. 219 - 226
Copyright
Copyright © Proprietors of Journal of Dairy Research 1970

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References

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