Sicurezza alimentare di prodotti ortofrutticoli di IV gamma

Introduction Vegetables are major components of healthy and balanced diet. However, 25% of foodborne diseases are linked to the consumption of vegetables, especially the minimally processed ready to eat (RTE) vegetables. The main foodborne pathogens associated at RTE vegetables are Enterobacteriaceae (E. coli, Salmonella spp. and Yersinia spp.) and psychrophilic microorganisms like Listeria monocytogenes. Aim of study The aim of this work was to assess the microbiological risks associated with consumption of RTE salads, through the quantification of microbiological contamination. In addition we carried out the rapid detection of foodborne pathogens by real time PCR, and molecular characterization of Listeria monocytogenes strain isolated in this study. Microbiological and bio molecular challenge tests was carried out for assess potential growth of Listeria monocytogenes in vegetables stored at different temperatures. Besides, the work was focused on the evaluation of washing process in association to the shelf life of these products. Materials and methods A total of 300 pre-packaged mixed raw vegetable salads collected from retail premises (68%) and production plants (32%) were examined. Microbiological eligibility for human consumption (Reg CE 1441/2007) is based on three bacteriological parameters (Escherichia coli, Salmonella spp and L. monocytogenes). In order to assess the safety of RTE vegetables, all parameters required by law have been investigated. The contamination of vegetables from E. coli O157:H7, L. monocytogenes and Salmonella spp was also investigated by real time PCR. Furthermore, the pathogenic properties of L. monocytogenes have been evaluated by PCR assay (prfA, rrn, hlyA, actA, inlA, inlB, iap, plcA e plcB). The purpose of Challenge test was to provide information especially on the behavior of L. monocytogenes. Results and conclusion Parsley and mixed salads showed the most contaminated panel, however we found high levels of contamination by Enterobacteriaceae in every kind of RTE salads. Salmonella spp. and E. coli O157:H7 have never been isolated, while only a sample of rocket was contaminated by one strain of L. monocytogenes and Yersinia enterocolitica. The PCR assay showed the virulence genes of L. monocytogenes strain (prfA, rrn, actA, inlA, inlB, plcA, plcB). Washing temperature, microbiological quality of water and raw material are basic requirements to achieve high microbiological standards for RTE salads. Listeria monocytogenes shows a growth potential variable in consideration of the different types of products and storage temperatures. Bio molecular challenge tests appear a useful tool for the evaluation of the survival of L. monocytogenes when coltural results seem uncertain (eg. high or low bacterial growth and difficulty in estimating the growth plate).