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Effect of psychrotrophic post-pasteurization contamination on the keeping quality at 11 and 5 °C of HTST-pasteurized milk in the UK

Published online by Cambridge University Press:  01 June 2009

Monika J. A. Schröder ,
Christina M. Cousins  and
Charles H. McKinnon
Monika J. A. Schröder
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9 AT, UK
Christina M. Cousins
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9 AT, UK
Charles H. McKinnon
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9 AT, UK
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Summary

The keeping quality of commercial HTST-pasteurized milk and laboratory pasteurized milk from a common bulk raw supply has been investigated for 5 dairies. Spoilage occurred at levels of total bacterial counts around 107 colony forming units/ml, but with a slightly higher off-flavour threshold for the commercial milks than the laboratory pasteurized milks. The predominant microflora at spoilage and the type of off-flavour produced differed between the 2 types of milk. Raising the storage temperature from 5 to 11 °C caused a slight shift in the spoilage microflora and led to an average reduction in the shelf life of the laboratory pasteurized milk from 28 to 6 d and of the commercial pasteurized milk from 13 to 5 d. Changes in the level of post-pasteurization contamination (PPC) were reflected in changes in keeping quality, particularly at 5 °C. However, the greatest improvements were found in the absence of PPC.

Type
Original Articles
Information
Journal of Dairy Research , Volume 49 , Issue 4 , November 1982 , pp. 619 - 630
Copyright
Copyright © Proprietors of Journal of Dairy Research 1982

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References

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