DINAMICA DI COMPORTAMENTO DI MICRORGANISMI PATOGENI IN CONFEZIONI DI MOZZARELLA DI BUFALA ARTIFICIALMENTE CONTAMINATE

The aim of this survey was to evaluate the behaviour of Listeria monocytogenes, Salmonella typhimurium, Staphylococ- cus aureus, Escherichia coli O157:H7 in packaged Water-Buffalo mozzarella cheese. Through two successive trials, the conditioning liquid was contaminated with a mixtures of these microorganisms. During the first trial contaminated samples were stored at 20°C for 6 days; in the second samples were stored at four different temperatures for variable times. The results showed that Sta- ph. aureus is not a risk to the consumer because its concentration reduced at all different storage conditions and the toxin is never produced. Salmonella typhimurium and E. coli O157:H7 concentration increased only at 20°C but after the end of the shelf-life period established by producers (5 days). In other storage conditions the concentration of both pathogens didn't modify or even decreased. L. monocytogenes decreased at 5°C, while in other storage conditions, after a lag phase variable depending on temperature, the bacterium showed the capability to grow.