Microbiological Quality of Plant-based Meat-alternative Products Collected at Retail Level in Switzerland

As the interest in plant-based alternative food products has increased significantly in the last years, it is also important to investigate these products regarding microbiological aspects. The aim of this study was to assess the microbiological quality and the occurrence of selected foodborne pathogens in plant-based meat alternative products (PBMA) collected at retail level in Switzerland. A total of 100 PBMA (84 vegan and 16 vegetarian products) was analyzed qualitatively for the presence of Salmonella, Listeria monocytogenes and quantitatively for Staphylococcus aureus, Bacillus cereus group members, Enterobacteriaceae, and the total viable count. Furthermore, pH measurements were carried out and the a_w-value was determined. Isolates were further analyzed with Whole Genome Sequencing. The total viable count before the expiration date was between <2 log and 7 log CFU/g (median: 5.97 log CFU/g). In six (6%) samples, Enterobacteriaceae with 2 log to 3 log CFU/g were detected. No Salmonella and no Listeria monocytogenes were detected. However, seven products (7%) were contaminated with other Listeria spp. (six L. innocua and one L. seeligeri). Further findings were two (2%) Staphylococcus aureus ST8 with the presence of selx and tsst-1 genes, and five (5%) Bacillus cereus group members (three B. paranthracis, one B. cereus sensu stricto, and one B. cytotoxicus) which all were diarrhea-associated strains. This study provides data that are relevant for HACCP concepts of companies that produce plant-based meat alternative products and helps to define microbiological parameters that should be included when testing such products.