Changes in glycosylation patterns of monoterpenes during grape berry maturation in six cultivars of Vitis vinifera.

Plants conjugate monoterpenoids to sugars, rendering them non-volatile. Hydrolysis of these glycosidic precursors frees the volatile aroma compounds. Here, we profile intact monoterpenyl glycosides in six Vitis vinifera grape berry cultivars. Relative concentrations of twenty-six monoterpenyl glycosides, including nine new putatively identified compounds, were analyzed by UHPLC-QTOF MS/MS at three times during grape maturation (pre-véraison, véraison, and post-véraison). Total glycoside content reached a maximum in Muscat cultivars post-véraison but remained relatively constant in all other cultivars. Three types of monoterpenyl glycosides predominated in all samples: malonylated monoterpenol glucosides, monoterpenol hexose-pentoses, and monoterpendiol hexose-pentoses. The two Muscat cultivars were not differentiated at the earlier developmental stages but could be differentiated post-véraison. In contrast, similarities between Chardonnay and Pinot noir glycoside profiles developed post-véraison. Overall monoterpene glycoconjugation patterns may align with underlying genetic relationships among cultivars. By understanding monoterpene glycoconjugation in wine grapes, scientists and winemakers can better understand grape and wine aromas.