Italian cheeses Targeted loci environmental. food metagenome

Italian PDO (Protected Designation of Origin) Fiore Sardo (FS), Pecorino Siciliano (PS) and Pecorino Toscano (PT) ewes’ milk cheeses were chosen as hard cheese model systems to investigate the spatial distribution of the metabolically active microbiota and its effect on proteolysis and synthesis of volatile components (VOC). Cheese slices were divided in nine sub-blocks, each one separately subjected to analysis and compared to the whole cheese slice (control). Gradients for moisture, and concentrations of salt, fat and protein were found within sub-blocks, while the cell density of the principal microbial groups did not differ. Secondary proteolysis differed between sub-blocks of each cheese, especially when the number and area of hydrophilic and hydrophobic peptide peaks were analyzed. The concentration of free amino acids (FAA) agreed. Regardless of the cheese variety, the poorest profile of VOC was restricted to the core E region as determined through PT- GC/MS. As shown through pyrosequencing of the 16S rRNA targeting RNA, the spatial distribution of the microbiota within cheeses was agreement with the VOC distribution, and differences were evident between core and the rest of the cheese. Top and bottom under rind sub-blocks of all three cheeses harbored the widest biodiversity. The cheese sub-block analysis allowed to reveal the presence of a sub-core microbiota, which was statistically correlated with secondary proteolysis event and/or synthesis of VOC. The differential spatial distribution of the metabolically active microbiota was, in most of the cases, attributed to evident deterministic factors, not excluding a stochastic effect.