Free Monoterpene Isomer Profiles of Eight Vitis vinifera L. cv. Varietal White Wines
Mei Song, Claudio Fuentes, Athena Loos, and Elizabeth Tomasino*
*Oregon State University, 100 Wiegand Hall, Corvallis, OR 97331
Monterpene compounds are important to varietal white wines, but the isomer profiles of these compounds are less well known. This study evaluated the mono-terpene isomer profiles and enantiomeric percentages of white wines from diverse grape varieties. One hundred forty-eight wines, including Chardonnay, Gewürz-traminer, 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 headspace-SPME-MDGC-MS. Linalool oxide isomers characterized Chardonnay, Pinot gris, and Sauvignon blanc wines. α-Terpineol, linalool, and linalool oxide isomers were abundant in Gewürztra-miner, Muscat, Torrontes, and Viognier wines. Linalool oxide and α-terpineol showed higher concentrations in Riesling wines. Interestingly, the isomers of each compound had very similar profiles in the same varietal wine. Separation between varieties was achieved using discriminant analysis in spite of high variability among vintage, region, and wine style. The difference in monoterpene isomer pro-file and enantiomeric percentages in varietal wines may contribute to the sensory differences among these wines.
Funding Support: Oregon Wine Board, Oregon Wine Research Institute