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Traditional Minas cheeses are very popular in Brazil. These cheeses are of two types: artisanal ripened semi-hard cheeses (HC) produced with raw milk and refrigerated fresh soft cheeses (SC) generally produced with pasteurized milk. Purpose: This study estimates the risk of listeriosis due to HC and SC consumption using quantitative microbial risk assessment (QMRA). Methods: QMRAs were developed for both cheese types. The HC model contained a module for predicting Listeria monocytogenes decline during ripening. The SC model contained a refrigerated storage module for predicting L. monocytogenes growth during storage. HC modeling scenarios varied L. monocytogenes starting concentration over -2.4 to 6 log CFU/ml in raw milk and three ripening times (4, 22, and 60 days). SC modeling scenarios varied L. monocytogenes starting concentration (-2.4 to 4 log CFU/ml in milk). Inclusion of antilisterial lactic acid bacteria (LAB) was also examined. Simulations (100,000 iterations per scenario) were carried out using the @Risk add-in for Excel. Results: Aging HC reduced risk, and risk was influenced by L. monocytogenes starting concentration. Aging 22 days with inhibitory LAB reduced risk more than 4 million-fold when L. monocytogenes was assumed to be 6 log CFU/ml in raw milk, and was lower risk than HC made without LAB and with a starting concentration of 1 log CFU/ml in raw milk. Inclusion of inhibitory LAB reduced risk of listeriosis from SC, but not as dramatically as for HC. Relative risk to vulnerable populations reduced 4.4 and 3.4-fold when L. monocytogenes starting concentrations were 1 log and 4 log CFU/ml in milk, respectively. Significance: The results of the QMRA predict that consumption of contaminated Minas cheeses can present a high risk of listeriosis, especially for vulnerable populations. Scenario analyses indicate that aging of HC and inclusion of LAB in HC and SC are effective risk mitigation measures. info:eu-repo/semantics/publishedVersion

This study aimed to compare the kinetic parameters of L. monocytogenes during refrigerated shelf-life of soft Minas cheese produced with raw or pasteurised milk, and with or without addition of a cocktail of selected LAB (starter). A dynamic tertiary model based on the Huang and the cardinal parameter models, adjusted to each of the four treatments, determined that the slowest growth (0.0281 In CFU/g h-l) and the lowest carrying capacity (14. 12 In CFU/g) of L monocytogenes in Minas cheese was obtained by adding the tailored culture to raw milk. info:eu-repo/semantics/publishedVersion

Introduction: Brazilian artisanal cheeses, among them Minas cheeses, are highly appreciated by consumers. Nonetheless, some cheeses have been regularly found to harbour high-risk pathogens, such as Listeria monocytogenes, mainly arising from their elaboration with raw milk and informal production. However, cheese matrices are complex systems whose microbial competing factors (i.e., indigenous lactic acid bacteria (LAB)) and intrinsic properties (acidity, temperature, and water activity) can act as effective hurdles against L. monocytogenes proliferation. Purpose: The aim of this study was to evaluate the capacity of LAB strains isolated from Minas artisanal cheeses as anti-listerial agents. Methods: A total of 891 LAB strains were isolated from 244 Minas artisanal cheese samples (466 using MRS agar (MRSLAB) and 425 using M17 agar (M17LAB)), which were tested qualitatively for anti-listerial activity by the deferred antagonism assay at 30oC (24 h). Two L. monocytogenes strains, serotypes 1/2b and 4b, isolated from cheese and crude milk, respectively, were used. LAB strains with positive anti-listerial activity at 30oC were further tested at 7oC (10 days). Results: MRSLAB strains presented significantly better anti-listerial activity at 30oC (73.0% and 70.8% for serotypes 1/2b and 4b, respectively) compared to M17LAB strains (21.2% and 23.1%, respectively), and there was no significant difference between listeria serotypes (P