The scents of aromatic white wines like Riesling, Gewurztraminer, Pinot gris and others seem to leap out of the glass into your nose. Winemakers often seek full expression of these attractive aromatic qualities in white wines and approximately 550 volatile compounds have been identified in grapes and wine with many contributing to the aromatic qualities in wine. Terpene compounds are among the most expressive of the aromas that include floral, rose-like, coriander, camphorous, green and herbaceous.
Dr. Elizabeth Tomasino is a sensory scientist in the OSU Food Science and Technology department and the Oregon Wine Research Institute. An Oregon Wine Board-funded project has taken her around the world in search of chiral terpene compounds in aromatic white wines. These compounds are found in grapes and when released during fermentation they create the familiar citrus and floral notes in white wines. Dr. Tomasino wondered if the aromatic qualities of a Riesling grown in Germany would be similar to a Riesling from the Willamette Valley, and whether the amount and type of chiral terpenes would be a unique terroir signature of aromatic white wines.
To investigate these relationships she collected 203 Riesling and Pinot gris wines from Australia, New Zealand, Germany, France, Italy, New York, Washington and Oregon. With the assistance of graduate student Mei Song, Dr. Tomasino analyzed the wines for 15 mono-terpene compounds using an advanced form of GC-MS technology.
They discovered some interesting facts about these aromatic compounds. Some, for example, that cause lilac and coniferous aromas were present in all wines but others with floral, green and herbal characteristics were not. Monoterpene levels and type varied according to location – Oregon Pinot gris terpenes, which impart strong leafy and earthy aromas more closely resembled those in Washington than those from New Zealand, New York or Italy. In 200 Riesling wines they found variability in terpene quantities based not only on where the wine was made but also by wine age and relative sweetness.
Eventually, Dr. Tomasino would like to determine the origin of terpene compounds and whether they can be manipulated in the vineyard or in the cellar to affect the aromatic profile of white wines.