Growth modelling of Listeria monocytogenes and Yersinia enterocolitica in food model systems and dairy products.

The growth potential of Listeria monocytogenes, measured with a gaschromatographic method, was evaluated in model systems simulating dairy products in which NaCl concentration, pH and lipid concentration ranged from values corresponding to matured hard cheeses to some light cheeses and other dairy products. The growth data from the model systems, calculated on the basis of the polynomial models obtained, were compared with values observed for dairy products. Growth parameters of Yersinia enterocolitica in traditional and light cheeses were also available. The comparison between predicted and observed data suggested that individual or interactive effects of chemicophysical variables such as pH, salt and lipid concentration are not sufficient to predict the fate of L. monocytogenes in dairy products. Microstructural factors as well as the pH effect on water binding capacity of proteins could also be implicated.