Behaviour of Listeria Monocytogenes in Artisanal Raw Milk Pecorino Umbro Cheese: A Microbiological Challenge Test

Microbiological Quality of Slovak Traditional Cheese

The aim of this study was to investigate the micro-biological quality of traditional Slovak “bryndza” cheese made in Slovakia. Besides the common pathogenic bacteria, we focused on the analyses of verocytotoxigenic Escherichia coli (VTEC), the occurrence of which has been analysed only occasionally in a few products. As we chose food of the highest risk which contained raw milk, we expected several positive findings. The presence of Salmonella spp., Listeria monocytogenes and Campylobacter spp. was not confirmed. The enumeration of Staphylococcus aureus was more successful. In the case of VTEC stx and eae screening, the presence of genes producing verocytotoxins vtx1, vtx2 and the gene encoding virulent factor intimin—eae in nine samples by molecular-biological methods were revealed. Only one isolate, which carried genes vtx1 a vtx2 and did not belong to these serogroups: O157, O111, O26, O103, O145, or O104, was detected by confirmation assays.

Thermal Inactivation and Growth Potential of Listeria Monocytogenes in Smoked Tench

An experimental study for the evaluation of Listeria monocytogenes inactivation during a hot smoking process in tench was performed using Listeria innocua strains. Furthermore, the survival of L. monocytogenes in smoked tench was determined after post-processing in contaminated samples, evaluating the growth potential during storage. L innocua was not detected after the smoking process. In the challenge test, the growth potential of L. monocytogenes was 5.68 log colony forming unit g-1. The results showed that hot smoking at an inner temperature around 72°C is able to eliminate the microorganism. Nevertheless, the product is able to support the growth of the pathogen if post-process contamination occurs, as the food is suitable for Listeria multiplication. Product recontamination should be prevented by means of appropriate application of hygiene measures.