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471. The role of micro-organisms in dye-reduction and keeping-quality tests: I. The change in dominant bacterial flora during incubation at 37·5 and 22° C. and the part played by staphylococci and the coli-aerogenes group

Published online by Cambridge University Press:  01 June 2009

Ellen I. Garvie  and
A. Rowlands
Ellen I. Garvie
Affiliation:
National Institute for Research in Dairying, University of Reading
A. Rowlands
Affiliation:
National Institute for Research in Dairying, University of Reading
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Extract

1. The present work was planned to provide an explanation of the lack of correlation for individual samples between the results of dye-reduction tests at 37·5° C. and keeping-quality tests at 22° C. A special study was made of the particular part played by the staphylococci (in thirty-eight samples) and the coli-aerogenes group (in thirty-seven samples) in dye reduction at 37·5° C. and in keeping quality at 22° C. A detailed study was also made of the changes in bacterial flora of twelve samples during incubation at these temperatures.

2. In milk, after overnight storage at 14° C., staphylococci were found to constitute only a small proportion of the bacterial flora, but their numbers increased during incubation at 37·5° C. (for the dye-reduction test) and at 22° C. (for the clot-on-boiling test). At the time of dye reduction staphylococci were found to constitute a major part of the bacterial flora, particularly in samples taking 5 hr. or more to reduce the dye. Although the staphylococci increased in numbers during incubation at 22° C. they constituted only a relatively small proportion of the flora at the time of the end-point of the clot-on-boiling test.

3. Initially the coli-aerogenes group were found to constitute only a small proportion of the total bacterial flora. Some growth usually occurred during incubation at 37·5 and 22° C.

Type
Original Articles
Information
Journal of Dairy Research , Volume 19 , Issue 2 , June 1952 , pp. 133 - 152
Copyright
Copyright © Proprietors of Journal of Dairy Research 1952

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