Cheeseomics of Grana Padano PDO cheese: Microbial diversity and flavour profiles compared to non-PDO cheeses

Protected Designation of Origin (PDO) schemes define technological constraints that may shape cheese microbiota and, consequently, volatilome and sensory quality. Here, a "cheesomics" approach to compare Grana Padano PDO (n = 13) with hard cooked cheeses of the same type and ripening time (9 months) produced outside the PDO framework (non-PDO; n = 15). Shotgun metagenomics was used to characterize bacterial and fungal communities and functional profile, while the volatilome was profiled by HS-SPME/GC-MS and sensory attributes were evaluated by trained ONAF panelist. A subset of samples (4 PDO and 4 non-PDO) was further analysed by flash profiling. Lactic acid bacteria dominated all samples, but distinct community and functional signature differentiated PDO and non-PDO cheeses. Grana Padano PDO showed higher sensory scores for odor/aroma and taste (p-value < 0.05), together with a more consistent microbiological profile. Non-PDO cheeses were more heterogeneous and displayed higher abundance of lipid-derived volatiles, including short- to medium-chain free fatty acids and methyl ketones, whereas PDO samples were associated with compounds such as pentanal and 2,5-dimethylpyrazine. Multivariate integration of taxa, VOCs and sensory data revealed partial separation between groups, supporting group-specific co-variation patterns. Functional profiling showed higher contributions (p-value < 0.05) of fermentation-related functions and cellular/extracellular polysaccharides in PDO cheeses, suggesting that sensory performance is not driven by VOC abundance alone. Fungal DNA was detected at very low level and showed limited relevance from a dairy microbiology perspective. Overall, the PDO production framework was associated with a measurable microbiological and metabolic imprint and with enhanced sensory performance relative to comparable non-PDO cheeses.