Abstract
'Chenin blanc' grape leaf volatile compounds were isolated by steam distillation. The distillate collected was extracted with pentane, and the compounds present were identified by gas chromatography/mass spectrometry. Prominent in grape leaves are the six-carbon compounds: cis-2-hexenal, trans-2-hexen-1-ol cis-3-hexen-1-ol, n-hexanol, trans-2-hexenol-1-ol, and cis-or trans-hexa-2,4-dienal. Also prominent are the terpenes and their derivatives: myrcene, linalool, alpha-terpineol, isopulegone, citral, geraniol, and ionone. Also identified were the sulfurcontaining compounds tetrathiocane and cis- or trans-3,5-dimethyl-1,2,4,-trithiolane. Sensory evaluation of the compounds exiting from gas chromatographic columns indicated that the six-carbon compounds were largely responsible for the "grassy" flavor from the leaves.
To confirm the influence of grape-leaf six-carbon compounds on wine grassy flavor, trans-2-hexenal, trans-2-hexenol, cis-3-hexenal, and n-hexenol in wine were evaluated by a taste panel. At 10 ppm or less, the compounds were detected at the 1% level of significance. To indicate whether six-carbon and other compounds might be released by macerated leaves in winemaking, wines were produced from grape juices containing 2% w/v leaves of which 0, 5, 15, and 25% w/w had been macerated. Taste-panel sensory evaluation of the wines indicated that 5% or more leaf maceration yielded wines of significantly lower quality.
- Accepted August 1975.
- Published online January 1975
- Copyright 1975 by the American Society for Enology and Viticulture