1H NMR-based characterization of the aqueous extract of aged Toma Piemontese PDO Cheese: Qualitative impact of gaseous ozone to control surface microbiota versus normal ripening conditions

Toma Piemontese PDO is a semi-hard cheese with strict production specifications. This study investigates the potential of 1 H NMR analysis to characterize the main metabolites in the cheese aqueous extract as a function of maturation time and different ripening conditions. Two gaseous ozone concentrations were applied to control surface microbiota: 300 ppb (0.642 mg m -3 ) for 8h/d and 400 ppb (0.856 mg m -3 ) for 8h/d on alternate d, compared to an untreated control (CTL). Results showed increases in butanone and glutamate over time for all samples. Ozone reduced the spoilage microbiota. This was reflected in 1 H NMR results: higher sugar hydrolysis in the CTL sample indicated greater fermentation activity. Higher threonine content was found in ozone-treated samples at the initial and final aging times, suggesting different proteolytic activity related to the production of acetic and propanoic acids. No differences in key aroma compounds were observed between treatments.