Exploring putative kokumi oligopeptides in classic sparkling wines with a UHPLC-ESI-MS/MS targeted protocol

Some oligopeptides can impart kokumi flavor to foods and beverages, a topic still not addressed in wine. A targeted ultra-high performance liquid-chromatography-mass spectrometry (UHPLC-MS/MS) metabolomics method capable of quantifying both amino acids and oligopeptides in wines was therefore developed and validated, confirming the presence of 50 oligopeptides in wine, most of which had been previously unexplored. In silico screening of the affinity of these oligopeptides to interact with CaSR, the protein necessary to activate kokumi sensations, highlighted 8 dipeptides and 3 tripeptides as putative kokumi compounds. These compounds were ubiquitous in a representative set of Trentodoc classic method sparkling wines, with an average concentration of kokumi oligopeptides of 19.8 mg/L, ranging between 9.1 and 33.3 mg/L. Half of the sparkling wine samples also contained glutamic acid at concentrations equal to or greater than the threshold for the umami taste in wine, namely, 48 mg/L. Sensory tests on the dipeptide Gly-Val confirmed the ability of this novel kokumi compound to significantly modify the perception of complex real wine matrices but not of the simple model one. Preliminary laboratory-scale fermentation tests showed that the oligopeptide profile in wines is linked to the starting grape matrix and that the patterns change by fermenting barley or apple juice with the same yeast