Kanako Sasaki,* Harumi Kikuchi, Hideki Takase, Mitsuhiro Anzo, and Takayoshi Katayama
*Kirin Holdings Company, Limited, 4-9-1 Johnan, Fujisawa, Kanagawa, 251-0057, Japan (Kanako_Sasaki@kirin.co.jp)

Muscat Bailey A is a hybrid grape variety (Vitis labruscana [Bailey] × Vitis vinifera [Muscat Hamburg]) that was hybridized in Japan in 1927. This variety has been cultivated since then and is one of the most popular red wine varieties in Japan. The inclusion of Muscat Bailey A on the International List of Vine and Varieties and their Synonyms managed by the International Organisation of Vine and Wine in 2013 has further fueled its popularity among winemakers and researchers around the world. Most Muscat Bailey A wines have unique characteristics, such as light mouth feel and strawberry-like, fruity aroma.  Our previous reports demonstrated that Muscat Bailey A grapes biosynthesize and accumulate 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), suggesting that HDMF may be responsible for the characteristic strawberry-like aroma of the wine. In addition, we identified HDMF glucopyranoside in Muscat Bailey A juice as the aroma precursor of HDMF. Here, we investigated the effect of shade-dried grapes vinification on the concentration of HDMF in Muscat Baliey A wines to enhance this characteristic aroma. The concentration of HDMF glucopyranoside in Muscat Bailey A juice increased remarkably with the shade-dried treatment. The result of real-time RT-PCR showed that the expression level of the HDMF glucosyltransferase gene (UGT85K14) in Muscat bailey A berries was much greater after the shade-dried treatment than before. These findings are expected to contribute to the understanding of the metabolism of HDMF in grapes and the control of the characteristic strawberry-like aroma of Muscat Bailey A wines.

Funding Support: Kirin Holdings Company, Limited