Predictive microbiology of dairy products: influence of biological factors affecting growth of Listeria monocytogenes.

The growth potential of Listeria monocytogenes was evaluated at low temperature in sterilized milk and raw dairy products. Sterilized and raw milk were inoculated with different strains of L. monocytogenes in 2 physiological states and at various contamination levels. Raw cheese was naturally contaminated with Listeria spp. The results suggest that some biological factors influence the growth capacity of L monocytogenes in dairy products. Significant strain effect was observed at low temperature whatever the growth medium. By contrast, no inoculum effect was observed in the 3 dairy products. In raw matrixes, growth of L. monocytogenes was influenced greatly by bacterial interactions and physiological state of inoculum cells.