Article pubs.acs.org/JAFC
Vineyard and Fermentation Studies To Elucidate the Origin of 1,8Cineole in Australian Red Wine Dimitra L. Capone,*,†,‡ David W. Jeffery,‡ and Mark A. Sefton‡ †
The Australian Wine Research Institute, P.O. Box 197, Glen Osmond, South Australia 5064, Australia School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, PMB 1, Glen Osmond, South Australia 5064, Australia
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S Supporting Information *
ABSTRACT: Preliminary investigations revealed that the proximity of Eucalyptus trees to grapevines can directly influence the concentration of the aroma compound 1,8-cineole present in the corresponding red wines. For two different vineyards, the closer the grapevines were to the trees, the greater was the amount of 1,8-cineole in the wines elaborated from those grapes. This led us to carry out further studies to quantify the levels of 1,8-cineole found in grape berries, leaves, and stems at set distances from Eucalyptus trees over multiple vintages. Generally, the highest concentration of 1,8-cineole was found in the grapevine leaves, followed by grape stems and then grapes. In each sample type, we observed greater concentrations of 1,8-cineole in samples closer to the trees. Various fermentation treatments carried out with Shiraz grapes showed that matter other than grapes (MOG, e.g., Eucalyptus or grape leaves) could contribute significant amounts of 1,8-cineole to the finished wines. These studies confirmed that vineyard position and winemaking conditions can determine the 1,8-cineole concentration in red wine. The fermentation study also showed for the first time that the concentration of rotundone in red wine can be strongly influenced by grapevine leaves and stems in the ferment. KEYWORDS: 1,8-cineole, GC−MS, Eucalyptus trees, rotundone, wine aroma, red wine
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INTRODUCTION Australia is the native habitat of the Eucalyptus genus, but its home has expanded to many countries around the world, including China, India, and Brazil. Every continent apart from Antarctica has been populated by Eucalyptus trees.1 There are over 850 species of Eucalyptus grown around the world, and they can prosper in diverse climates.1 Eucalyptus trees have a multitude of uses in industries including cultivation of timber for construction, pulp, fuel, and essential oil production.1 Most species of Eucalyptus contain volatile essential oils in their leaves, although the bulk of the world’s Eucalyptus oil production comes from only six species.2 Depending on the species, the main component (60−90%) of the oil from most of these Eucalyptus trees is 1,8-cineole, commonly known as eucalyptol.2 Eucalyptus oils are present in numerous consumer goods, and 1,8-cineole has also been found as a component of red wine, where it has been described as “fresh”, “cool”, “medicinal”, and “camphoraceous”.3 The origin of 1,8-cineole in wine has not been verified, but several theories have been reported. Herve et al. proposed that the “eucalyptus” character in wines occurs when vineyards are adjacent to Eucalyptus trees,3 whereas Farina et al. used hydrolytic studies to propose that terpene compounds such as α-terpineol and limonene were precursors of 1,8-cineole.4 More recently, we showed that hydrolysis of limonene and αterpineol at wine pH gave very low molar conversions into 1,8cineole (
