Methoxypyrazines in Sauvignon blanc Grapes and Wines

Three methoxypyrazines were identified and quantified by gas chromatography/mass spectrometry in wine and juice samples of Vitis vinifera L. cv. Sauvignon blanc. Twenty-two wines of Australian, New Zealand, and French origin were analyzed together with 16 juice samples from four Australian regions. 2-Methoxy-3-(2-methylpropyl)pyrazine was present in all wines (0.6 - 38.1 ng/L) and all juice samples (0.6 - 78.5 ng/L); it was invariably the major methoxypyrazine. 2-Methoxy-3-(1-methylethyl)pyrazine was found in 11 wines (0.9 - 5.6 ng/L) and almost all juice samples (0.2 - 6.8 ng/L). In three wines and some juice samples, small quantities of 2-methoxy-3-(1-methylpropyl)pyrazine were found (typically 0.1 - 1.0 ng/L). Methoxypyrazine levels in the New Zealand wines were significantly higher than in the Australian wines (p < 0.001). Fruit grown under cool conditions gave higher grape methoxypyrazine levels than fruit grown under hot conditions. Grape methoxypyrazine levels were relatively high at veraison but decreased markedly with ripening.