Modification of cheese flavour through the use of surface microbiota

Surface microorganisms in surface-ripened cheese, combined with lactic acid bacteria, contribute to lipolysis and proteolysis, degradation of free fatty acids and free amino acids, and the metabolism of lactose, citrate and lactate, with a consequent biosynthesis of volatile flavour compounds. The intense metabolic activity of the yeasts and Gram-positive bacteria on the cheese surface is evident in surface-ripened cheese, where the resident surface microbial population is responsible for the characteristic strong flavour, typical for this cheese variety. Although cheese is a widely studied fermented food, the biochemical mechanisms which lead to the biosynthesis of volatile compounds, and the development of cheese flavour, are not completely clear and need to be explained. Therefore, the aim of the studies in this thesis was to investigate the development of flavour volatile compounds in cheese, produced by cheese microbiota, both as single strains in model systems, and when applied to cheese curd surface as simple or more complex culture mixes containing yeasts and Gram-positive bacteria. Through the use of the metagenomic and enzymatic assays, it has been possible to investigate the potential flavour-forming ability of the cheese microorganisms, and correlate the results to volatile flavour compounds detected with gas-chromatography. Our results have shown how variations in the microbial population influence the flavour development in cheese during ripening. This research may be of industrial benefit for the manipulation of the microbiota and the production of fermented food with specific flavour characteristics