Monoterpenes are volatile compounds in aromatic white wines. Several monoterpenes are chiral and have different isomers. These isomers are non-superimposable mirror images of each other, maintain the same molecular structure and in many instances possess different sensory characteristics. The aim of the study was to evaluate the monoterpene isomer profiles of white wines from diverse grape varieties. One hundred forty eight wines from eight grape varieties, including Chardonnay, Gewürztraminer, Muscat, Pinot gris, Riesling, Sauvignon blanc, Torrontes and Viognier, were collected from 2012 and 2013 vintages. Seventeen monoterpene isomers: S-(-)-limonene, R-(+)-limonene, (+)-(2R,4S)-cis-rose oxide, (-)-(2S,4R)-cis-rose oxide, (-)-(2R,4R)-trans-rose oxide, (+)-(2S,4S)-trans-rose oxide, (2R,5R)-(+)-trans-linalool oxide, (2R,5S)-(-)-cis-linalool oxide, (2S,5S)-(-)-trans-linalool oxide, (2S,5R)-(+)-cis-linalool oxide, S-(-)-nerol oxide, R-(+)-nerol oxide, R-(-)-linalool, S-(+)-linalool, S-(-)-α-terpineol, R-(+)-α-terpineol, and R-(+)-β-citronellol were identified and quantified by head space-SPME-MDGC-MS. Results from general linear models displayed significant differences for the compounds among the eight grape varieties. Linalool oxide isomers were found to characterize Chardonnay, Pinot gris and Sauvignon blanc wines. α-Terpineol, linalool and linalool oxides isomers are abundant in Gewürztraminer, Muscat, Torrontes and Viognier wines. Linalool oxide and α-terpineol showed higher concentration in Riesling wines. Interestingly, the isomers of each compound had very similar profiles in the same varietal wine. A separation between varieties was achieved in spite of the high variability coming from vintage, region and wine style using discriminant analysis. Group 1 included Chardonnay, Pinot gris, Riesling, Sauvignon blanc and Viognier wines which contained lower concentrations of monoterpene isomers; group 2 comprised of Muscat and Torrontes wines which contained higher concentrations of isomers; group 3 contained only Gewurztraminer wines of which isomer concentrations intermediate in comparison to the other two groups. The different profiles of isomers may be important to the sensory differences in these wines and can be used by the industry as markers of varietal qualities.

Chiral monoterpene profiles of aromatic white wines

253rd National Meeting (2017)

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