Listeria monocytogenes growth potential in Ricotta Salata cheese.

"Ricotta salata is made heating at temperature above 85 °C the whey remaining after. cheesemaking of sheep milk cheese. L. monocytogenes post process contamination may occur. from the dairy plant environment. A microbiological challenge study was performed to assess. the growth potential () of L. monocytogenes in Ricotta salata cheese in accordance with the. Technical Guidance Document prepared by the EU Community Reference Laboratory for L.. monocytogenes. 36 Ricotta salata cheese were sprayed on the surface with a mixture of three. L. monocytogenes strains obtaining an inoculum level of ca. 102 cfu\/g and stored at. refrigeration temperatures until analysis. The study was conducted in three independent trials. using different production batches in order to account for product variation. Samples were. analyzed for the detection and enumeration of Listeria monocytogenes at 2, 4 and 6 months. after inoculation. The growth potential was calculated as the maximum difference between the. median of the log10 cfu\/g at the different test points and the median of the log10 cfu\/g at time. “0” (6 hours after the inoculation). The was 4.87 at 2, 6.90 at 4 and 6.20 at 6 months. respectively. These results indicate that Ricotta salata is a good substrate for L.. monocytogenes growth. The greater increase in the concentration of Listeria monocytogenes. was obtained during the first 2 months after the artificial contamination. Contamination. occurring in the processing environment could lead, even with proper chilled storage, to. levels of Listeria monocytogenes considered as a risk to public health. In order to obtain. compliance with the limit of 100 cfu\/g and to extend the shelf-life of the product it is crucial. the application of a post-lethality treatment before placing Ricotta salata on the market."