Survival of Listeria monocytogenes in a food colorant derived from red beets.
Three commercial lots of the red beet colorant were inoculated to contain circa 10(3) to 10(7) Listeria monocytogenes strains California, V7, or Scott A per milliliter and stored for 56 d at 7 degrees C. McBride listeria agar was used to determine numbers of survivors. Selected colonies thought to be L. monocytogenes were confirmed biochemically. When necessary, samples were tested by cold enrichment (up to 8 weeks). Samples of colorant initially containing 10(3) to 10(4) strain California/ml were always free of the pathogen after 56 d, and sometimes after 42 d. Samples with high initial numbers (10(5) to 10(6)/ml) were not free of the pathogen after 8 wk at 7 degrees C. Strains V7 and Scott A, regardless of size of initial population, always survived beyond 56 d. Before inoculation, all test samples of colorant were free of L. monocytogenes (direct plating or cold enrichment).
el-Gazzar
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Department of Food Science, University of Wisconsin, Madison 53706.
Marth
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D015169:Colony Count, Microbial; D005505:Food Coloring Agents; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000254:growth & development*; D010860:Pigments, Biological; D014675:Vegetables
D005505:Food Coloring Agents; D010860:Pigments, Biological