Ref: Herve, E.; Price, S.; Burns, G. Eucalyptol in wines showing a “eucalyptus” aroma. In Proceedings of the VIIeme Symposium International d’0enologie; Actualites 0enologiques: Bordeaux, France, 2003.
New Capabilities at ETS
“Eucalyptus” character is one of the most notable and controversial sensory expressions in some of California’s most prominent wines. Its presence is often related to eucalyptus trees growing near the vineyard area.
ETS has conducted research that has linked the “eucalyptus” aroma to the presence of eucalyptol (1,8-cineole) and has developed a method to detect and quantify its concentration in wine.
Analysis of eucalyptol is a powerful tool to measure the impact of eucalyptus growing in the vicinity of the vineyard, and to assist winemakers in objectively documenting their sensory impressions.
Significance of eucalyptol in wine
Eucalyptol (1,8-cineole) has a “fresh”, “cool”, “medicinal” and “camphoraceous” odor. It is the main component of the distinctive odor found in most eucalyptus species and represents 65 to 75% of the leaf oil from E.globulus, the predominant eucalyptus species in California.
In our research study, eucalyptol was detected in a variety of wines exhibiting a “eucalyptus” aroma. The flavor, perceived during tasting, appeared to be strongly related to quantified concentrations of eucalyptol as high as 20 µg/L. Aroma thresholds for eucalyptol were determined using a California Merlot. The difference and recognition thresholds were 1.1 µg/L and 3.2 µg/L respectively.
The study clearly demonstrated that eucalyptol plays a major role in the occurrence of “eucalyptus” character in wine.
Eucalyptus trees may introduce eucalyptol to grapes by airborne transfer
The likely origin of eucalyptol in wine is via airborne transfer from eucalyptus tees to grape berries in the vineyards. Eucalyptol released into the atmosphere may be adsorbed by wax on the berry surfaces. It is subsequently dissolved during fermentation on the skins or extended macerations. This theory is supported by the observation that a “eucalyptus” character is rarely experienced in white wines.
A simple experiment confirmed the validity of this hypothesis. Cabernet Sauvignon berries were placed into a sealed jar containing one eucalyptus leaf for five days. The leaf was not in direct contact with the berries. Eucalyptol was detectable in the berries after this relatively short amount of time, while not detected in the control jars of cabernet berries without eucalyptus leaves.
ETS has developed a method for quantifying eucalyptol in wine samples using an automated GC/MS system. The method allows detection below sensory thresholds with excellent precision.
Consequences and Applications
Monitoring eucalyptol content is a useful way to manage a significant flavor component in finished wines. Winemakers who wish to minimize or maintain consistent levels of “eucalyptus” character will benefit by determining eucalyptol concentrations in distinct wine lots.
Vineyard managers can use this tool to characterize vineyards close to eucalyptus groves and assess the impact of eucalyptus tree removal.
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