One of the increased concerns of wine industry is related to vine stress. Although the off-flavor descriptors vary from winery to winery, the frequent descriptors used in the wineries include “tequila”, “shellfish”, “peanut”, “ashtray”, “dry weed”, “herbaceous’, “flint” and other descriptors. In young wine, the taint smells like “bay leave”, and the wines do not age well. There were observations from wineries that taint could be related to compromised or nutritionally imbalanced fruits from stressed vines, induced by drought, nitrogen deficit, or a combination of many factors, but the exact cause(s) has never been studied or documented. This research is aimed at identifying the chemical nature of these off-flavors using gas chromatography/olfactometry, GC-MS and sensory analysis. Once the chemical nature of the off-flavor is identified, viticulture and enology remedies could be further investigated. The objective for the first year is to identify wine sensory characteristics that define “stress vine syndrome” through sensory evaluation and to identify wines for further analysis.
Several wines have been identified from industrial collaborators. Rollin Soles from ROCO winery identified a matured vineyard with full cover crop and dry farming practice to give a wine with bay leaf aromatic (2012 vintage) and the taint intensified with aging. Another vineyard with young vine also repeated to give dried herb tequila aromatics. Gary Horner from Erath winery also identified several wines with stressed vine aromatics including Pinot noir, Pinot gris and Chardonnay. More off-flavor wines are being recruited.
The “stressed vine” off-flavor was characterized by a sensory panel consisted of six winemakers from the Willamette Valley who have been involved with “stressed vine” off flavors previously and five OSU researchers involved in the project. The panel was able to identify the “stressed vine” off-flavor from the wines collected from industry. The off-flavor was also compared with wine standards comprised of tequila, peanut shell, bay leaf, agave and herbal characteristics. The off-flavored wine and the standards will be used for further sensory training and analysis.
Some preliminary chemical analyses were also performed in these wines including higher alcohols, esters, volatile phenols and TDN (kerosene aroma). The analyses were also performed on 20 normal Pinot noir wines. Data are being analysis to compare the off-flavored wine with the normal wines. GC/olfactometry will be performed next to identify the off-flavor compound(s) in “vine stressed” wines.