S-3-(hexan-1-ol)-Glutathione (3MH-S-glut) and S-3-(hexan-l-ol)-l-cysteine (3MH-S-cys) concentrations in grape berry from Vitis vinifera cv. Koshu grown in four vineyards by liquid chromatography-tandem mass spectrometry were analyzed. Commercial yeast strains converted 3MH-S-glut and 3MH-S-cys into 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), suggesting that both 3MH-S-glut and 3MH-S-cys are the flavor precursors of 3MH. Experiments conducted with a fermentation model showed that 3MH-S-cys was more effective in releasing volatile thiols than 3MH-S-glut. 3MH-S-glut and 3MH-S-cys were scarcely accumulated in stem and seed, but were accumulated in leaf and berry from 11 weeks postflowering (wpf). Leaf had the highest 3MH-S-glut and 3MH-S-cys contents among the grapevine tissues tested throughout development. In Koshu grape juice, the accumulation of both compounds peaked at 16 to 18 wpf and decreased thereafter. Cultivation conditions also affected 3MH-S-glut and 3MH-S-cys concentrations in grape berry. The accumulation of 3MH-S-glut and 3MH-S-cys in grape berry was the most rapid in the Kofu vineyard, which has the lowest elevation, and the slowest in Nirasaki vineyard, which has the highest elevation. These findings are expected to contribute to improving viticultural practices with the aim of harvesting grape berries having high concentrations of flavor precursors that are responsible for enhancing varietal aroma of Koshu wine.
- Koshu grape
- Koshu wine
- volatile thiol
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