Methoxypyrazine content of Japanese red wines

Three 2-methoxy-3-alkylpyrazines (MPs) in Japanese red wine and grape samples were determined by GC-EIMS, using 2-methyl-3-n-propylpyrazine as an internal standard. MPs in the Cabernet Sauvignon red wines were derived not only from the pulp but also from other parts of the grape berries, All of the Cabernet Sauvignon red wines made annually from 1975 to 1994 contained 2-methoxy-3-isobutylpyrazine (isobutyIMP), although those made from web-ripened grapes had a low isobutyIMP level. It is suggested that the climatic conditions of September might effect the isobutyIMP level of Cabernet Sauvignon grapes and red wines, The mean isobutyIMP level of Cabernet Sauvignon, Cabernet Franc, and Merlot Japanese commercial red wines was significantly higher than the mean isobutyIMP level of Muscat Bailey A and Zweigeltrebe.