Wines & Vines---Eucalyptus Aromas: A Mystery

I came across the article "Eucalyptus Aromas: A Mystery", in the February 2013 issue of Wines & Vines¹. It captured my interest because I read that Robert Mondavi's To Kalon Vineyards abuts a grove of eucalyptus trees and wines made from grapes that are closest to the eucalyptus often tastes of eucalyptus. In this article, the researchers from the Australian Wine Research Institute conducted various experiments to determine where the eucalyptus aroma and flavor came from.
The flavor comes from a chemical produced by the eucalyptus trees called, eucalyptol. Eucalyptol, also called 1,8-cineole is a monoterpenoid cyclic ether.²

Consumer studies showed that there was a preference for wines that were spiked with either 4 micrograms per liter (μg/L) or 30 μg/L of 1,8-cineole, with more consumers preferring the higher concentration. When 1,8-cineole was found in a wine, organoleptic descriptors such as "eucalypt", "camphor", "fresh", and "minty" were evoked. The researchers found that wines made from grapes growing closest to the eucalyptus grove contained more 1,8-cineole, but the 1,8-cineole came from the inclusion of eucalyptus leaves that was present in the machine harvested grapes and not from the eucalyptus oils on the grapes. From a series of experiments, it was determined that an addition of 4 eucalyptus leaves and a small piece of bark totalling 3.6 grams in 50 kg of hand harvested grapes resulted in a dramatic increase in the concentration of 1,8-cineole in the wine (30 μg/L).
If you find that you are tasting flavors of eucalyptus, camphor or mint, you might consider looking into the location of the vineyard from where the wine was made. I found this to be fascinating!
References:
1. Dimitra L. Capone, I. Leigh Francis, Markus J. Herderich and Daniel L. Johnson, Eucalyptus Aromas: A Mystery, Wines & Vines, February 2013, pg. 52-57.
2. Wikipedia entry for Eucalyptol.
All structures were drawn by the freely available drawing program from ACD Labs called ACD/ChemSketch Freeware.