Fermented sausages have a long tradition originating from Europe and they constitute a significant part of the Mediterranean diet. This kind of products has a specific microbiota that is typical of the region or area where they are produced. Therefore, in order to protect the traditional aspect of these products, it is essential to understand the microbial ecology during fermentation by studying the dynamic changes that occur and to select autochthonous starter cultures that can be used in the production. In this paper we summarize the state of the art concerning the selection and use of starter cultures and ecology aspects of naturally fermented sausages. We pay particular attention to the application of bacteriocinogenic strains as they could provide an additional tool in the prevention of foodborne pathogens as well as enhancing the competitiveness of the starter organisms. Microbial ecology of fermented sausages has been determined by traditional microbiological methods, but the introduction in food microbiology of new molecular techniques complements the studies carried out so far and allows scientists to overcome the limitations of traditional methods. Next Generation Sequencing (NGS) techniques represent a change in the way microbiologists address ecology and diversity in foods. Indeed the application of metataxonomics and metagenomics will permit a detailed understanding of microbial ecology. A thorough knowledge of the mechanisms behind the biological processes will enhance meat fermentation control and modulation to obtain products with desired organoleptic properties.

Metagenomics is a powerful tool to study and understand the microbial dynamics that occur during food fermentation and allows to close the link between microbial diversity and final sensory characteristics. Each food matrix can be colonized by different microbes, but also by different strains of the same species. In this study, using an innovative integrated approach combining culture-dependent method with a shotgun sequencing, we were able to show how strain-level biodiversity could influence the quality characteristics of the final product. The attention was placed on a model food fermentation process: Salame Piemonte, a Protected Geographical Indication (PGI) Italian fermented sausage. Three independent batches produced in February, March and May 2018 were analysed. The sausages were manufactured, following the production specification, in a local meat factory in the area of Turin (Italy) without the use of starter cultures. A pangenomic approach was applied in order to identify and evaluate the lactic acid bacteria (LAB) population driving the fermentation process. It was observed that all batches were characterized by the presence of few LAB species, namely Pediococcus pentosaceus, Latilactobacillus curvatus and Latilactobacillus sakei. Sausages from the different batches were different when the volatilome was taken into consideration, and a strong association between quality attributes and strains present was determined. In particular, different strains of L. sakei, showing heterogeneity at genomic level, colonized the meat at the beginning of each production and deeply influenced the fermentation process by distinctive metabolic pathways that affected the fermentation process and the final sensory aspects.

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