Scientific Analyses of The Origin of Koshu Grapes and The Flavor Compounds of Koshu Wine

Koshu, thought to be derived from a cross-breeding of Vitis vinifera L. and V. davidii Foex, is the most popular indigenous cultivar for wine production in Japan (2, 3).  Koshu seems to be 70% V. vinifera and the remaining 30% is derived from the Chinese wild species of V. davidii or a closely related species (2, 3).  The Koshu wine tested had high contents of 4-vinylphenol, likely to be responsible for the chemical smell, 2-Methoxy-4-vinylphenol, likely to be the source for the smoky aroma, β-damascenone, whose aroma is similar to that of apple compote, and 3-Mercaptohexan-1-ol (3MH), whose aroma is similar to those of grapefruit and passion fruit (6).  Furthermore, the environmental stresses enhanced the biosynthesis of two flavor precursors of 3MH, [S-(3-hexan-1-ol)-glutathione and S-(3-hexan-1-ol)-L-cysteine], in grapevine (6).  In the case of the amino acid composition, Koshu wine specifically contained glutamine compared to Chardonnay wine and higher concentration of proline than Chardonnay wine (9).  These findings may be useful for the selection of suitable cultivation conditions and the improvement of the quality of Koshu grapes and wine (1, 4, 5, 6, 7, 8, 10, 11).

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