Behaviour of Listeria monocytogenes in packaged water buffalo mozzarella cheese L. monocytogenes in mozzarella cheese

Aims: The aim of the study was to evaluate the behaviour of Listeria monocyt- ogenes in the conditioning liquid of packaged water buffalo mozzarella cheese (WBMC). Methods and Results: The conditioning liquid was contaminated with L. mono- cytogenes, and the contaminated samples were stored at four different storage temperatures: 5 and 10°C for 22 days; 20°C for 9 days; 20°C for 3 days and then at 5°C for 6 days. The results showed that L. monocytogenes concentration decreased when contaminated samples were stored at 5°C. When WBMC was stored at 20°C and at 10°C, L. monocytogenes started to grow after a lag phase of 3 and 10 days, respectively. When samples were stored at variable tempera- ture conditions, L. monocytogenes numbers showed a lag phase of 5 days. Conclusions: Use of a conditioning liquid characterized by acidity and a correct storage temperature is able to counteract pathogen replication during shelf life. A high concentration of lactic acid bacteria was associated with effec- tive control of L. monocytogenes but the role of lactic acid bacteria in WBMC conditioning liquid requires further investigation. Significance and Impact of the Study: According to European regulations, food producers should be able to justify decision-making on the shelf life assigned to their products, taking into account reasonable storage conditions and use by consumers. The results of the trial yielded information for producers of WBMC and similar cheeses for decision-making on product shelf life.