Frank Butera - Eucalyptus characteristics in red wine

Eucalyptus characteristics in Red Wine

By Frank Butera

hile native to Australia, Eucalyptus trees are now grown W throughout the world. Most species of Eucalyptus trees contain essential oils in their leaves and, depending on the species, the main component of the oil is a volatile compound called 1,8-cineole, commonly known as eucalyptol.

Hardy and resilient, they grow in a range of different climates and environments, providing raw timber and wood pulp, as well as large supplies of eucalyptus essential oil.

This compound is found above sensory detection thresholds in some red wines, where it is responsible for characters described as ‘eucalypt’, ‘camphor’, and ‘minty’. Whilst attending Pinot Noir conferences mostly from Victorian winemakers the minty character is at time detected.

For some winemakers these characters are a selling point, and their red wines are known for their ‘eucalypt’ sensory properties. That is a distinctive Australian wine and some eucalypt character in red wines lifts the aromatics in wine.

For others, however, ‘eucalypt’ characters are something they prefer to avoid, or at the very least limit through effective management strategies. Research on ‘eucalypt’ character in wine has focused on understanding the source of the character and providing options for winemakers to be able to control it.

Eucalyptus trees growing close to vineyards are the primary source of the flavour in wine. Grapes harvested from rows greater than 25 or 50 m from Eucalyptus trees gave wines with very low levels of 1,8-cineole whilst those grown close to the trees contained significant amounts of 1,8-cineole. The research also found that the compound is found in the skin of the berry, and is extracted during fermentation on skins, with white wines generally having negligible amounts.

Wine consumers response to eucalypt flavour in red wines was also investigated. Results showed that even at very low levels, most consumers reacted to the flavour, and interestingly more consumers liked wines with the ‘minty’ flavour than those who didn’t.

Further work showed that absorption of the compound by grape berries, while important, is much less a factor than the presence of Eucalyptus leaves or bark in harvested grapes. Machine harvesting of the rows closest to Eucalyptus trees will more than likely produce bins of grapes with numerous Eucalyptus leaves, and these have a very large effect on levels of 1,8-cineole in wine. Unexpectedly, grape leaves or grape stems were also a major source of the compound.

Investigations showed that grape skins contained much higher concentrations of 1,8-cineole than grape pulp and that grape stems and grape leaves had even higher levels. The confirms that airborne transmission was responsible for the transfer of 1,8-cineole – from Eucalyptus trees to the vines located close.

While not all Eucalyptus species have high levels of 1,8-cineole in their leaves, many of the common trees in winegrowing regions, such as Eucalyptus leucoxylon (Yellow Gum), have great potential to affect vineyards. In hindsight, it should not be too surprising that Eucalyptus leaves or bark falling from trees can be blown some distance by the wind to lodge in grapevine from vines growing near Eucalyptus trees separately and use this wine as a blending option; they can hand pick those rows closest to trees; or they can ensure that only grapes are included in harvest bins of grapes. Sorting tables, whether manual or automated, would also be effective.

The main message from the research is that avoiding material other than grapes in picking bins, especially Eucalyptus leaves, will dramatically reduce the level of ‘eucalypt’ flavour in wine.

The investigations suggest that Eucalyptus has a major impact on sensory characteristics of the final wine. Enhancing or reducing ‘eucalypt’ characters is no longer a case of pure chance and winemakers are in a much stronger position to take greater control of 1,8-cineole and adjust eucalyptus character to create wines that express their ‘terroir’.

Frank Butera is the wine maker at Bass River winery. Email frank@bassriverwinery.com Instagram @bassriverwinery