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Appl. Environ. Microbiol., Feb 1997, 448-453, Vol 63, No. 2
KJ Bjorkroth and HJ Korkeala
Molecular typing was applied to an in-plant lactic acid bacterium (LAB)
contamination analysis of a vacuum-packaged sliced cooked whole-meat
product. A total of 982 LAB isolates from the raw mass, product, and the
environment at different production stages were screened by restriction
endonuclease (EcoRI and HindIII) analysis. rRNA gene restriction patterns
were further determined for different strains obtained from each source.
These patterns were used for recognizing the spoilage-causing LAB strains
from the product on the sell-by day and tracing the sources and sites of
spoilage LAB contamination during the manufacture. LAB typing resulted in
71 different ribotypes, of which 27 were associated with contamination
routes. Raw material was distinguished as the source of the major spoilage
strains. Contamination of the product surfaces after cooking was shown to
be airborne. The removal of the product from the cooking forms was
localized as a major site of airborne LAB contamination. Food handlers and
some surfaces in contact with the product during the manufacture were also
contaminated with the spoilage strains. Some LAB strains were also able to
resist cooking in the core of the product bar. These strains may have an
effect on the product shelf life by contaminating the slicing machine. The
air in the slicing department and adjacent cold room contained very few
LAB. Surface-mediated contamination was detected during the slicing and
packaging stages. Food handlers also carried strains later found in the
packaged product. Molecular typing provided useful information revealing
the LAB contamination sources and sites of this product. The production
line will be reorganized in accordance with these results to reduce
spoilage LAB contamination.
Copyright © 1997, American Society for Microbiology
Use of rRNA gene restriction patterns to evaluate lactic acid bacterium contamination of vacuum-packaged sliced cooked whole-meat product in a meat processing plant
Department of Food and Environmental Hygiene, University of Helsinki, Finland. Johanna.Bjorkroth@Helsinki.fi
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