Abstract
The ripened or unripened soft, semi-hard, hard, or extra-hard product, in which the whey protein/casein ratio does not exceed that of milk, is by definition cheese. Cheese is made by coagulating all or some of the protein in milk and is one of the foundations of the global food industry. Since it was initially created in the Mediterranean region 7500 years ago, the product as we know it now is one of the oldest meals ever recorded, and its basic manufacturing process has not undergone any significant alterations. A crucial and extraordinarily complex step in the manufacture of cheese is the ripening process, which is the natural aging process that results from a chain of interactions that modifies the physical, biochemical, microbiological, and mainly sensory features of cheeses. In general, the biochemical processes involved in cheese ripening can be divided into primary events (such as the metabolism of residual lactose, lactate, and citrate, proteolysis, and lipolysis) and secondary events (such as the metabolism of fatty acids and amino acids), which are crucial for the emergence of aroma and flavor compounds in aged cheeses. For aged cheeses to develop a variety of desirable or unwanted properties, proteolysis is crucial for the sensorial aspects and characterization of these cheeses but also for the production of bioactive peptides. Therefore, the goal of this thesis is to investigate and define the physicochemical and microbiological profile of northern Italian cheeses at various stages of production using omic sciences, in order to advance knowledge of the cheese microbiome, the inherent qualities of each product, changes that occur during production, and associated sensory and nutritional effects. Regarding the metabolomic study on the Stelvio PDO cheese packed in a modified atmosphere, there were no significant variations in volatiles during storage in either situation, despite the fact that the different regions of Stelvio cheese exhibit distinctive patterns of volatiles that have an intriguing tendency over time. The olfactory profiles of the samples mostly stayed unchanged since there were minimal changes in how the fragrance elements responded to the storage circumstances throughout the Stelvio cheese samples. This supports the sensory data on acceptability and shows that storing the product under a vacuum or a modified environment is an effective packing technique to preserve the product's sensory qualities over an extended length of time. With the metagenomics study on Asiago PDO cheese we may infer that although milk has a far larger diversity of microorganisms than its derivatives, the starter naturally controls this diversity while making cheese. Thus, the crucial phases that defined the production and ripening of Asiago cheese were determined by this investigation. It was also possible to see that minor changes in biodiversity brought on by the use of various starter cultures or by intrinsically linked biotic and abiotic conditions at the location of cheese production may not have a significant impact on the production of total FAA or the overall proteolysis profile, but they may have an impact on the profile of individual FAA released, which in theory could slightly affect the volatiloma characteristics of cheese. About the peptidomic study on Asiago PDO cheese, we validated the starting culture's critical role in the temporal release of ACE-inhibitory peptides as well as the likely direct link between the genus Lactobacillus and these compounds. After three months of ripening, the industrial starter used in Dairy I ensured the maximum relative intensity of bioactive peptides, whereas the cheeses manufactured with lattoinnesto (Dairy II) did so at two months but with a lower overall relative intensity compared to Dairy I. However, Dairy II's sub-dominant strains and NSLABs are in charge of producing part ACE-inhibitory peptides, reiterating the significance and relevance of each microregion's indigenous strains even within a defined PDO production area. In conclusion, we were able to confirm the significance of various microbial groups known as dominant, sub-dominant, and satellite members throughout the entire cheesemaking process by utilizing special methodologies related to meta-omics approaches. This was done by utilizing a cutting-edge scientific method. It was shown how intricate and related cheese's microbiological traits are to its sensory, nutritional, and even bioactive components. Even in highly standardized goods that have a great deal in common, the profiles of volatile chemicals and the release of free amino acids revealed themselves to be rather reliant on the microbiota present in each sample. In addition, one of the most noticeable aspects of cheeses that have been fermented for a long time is the bioactive qualities of the peptides that are produced, which allows for the in-vivo study and clinical research that goes beyond the nutritional or industrial purposes of these goods.