rotundone is a key aroma compound responsible for the distinctive ‘spicy’, ‘peppery’ aroma in some red wines, particularly syrah/Shiraz from cooler climates. It has also been found in Grüner Veltliner. In red wines, it has a very low aroma detection threshold of 16 ng/l but as many as one in five people cannot smell rotundone, even at very high concentrations. Rotundone is an oxygenated bicyclic sesquiterpenoid compound that was originally discovered in the tubers of Cyperus rotundus, a species of sedge. It is also present in black and white peppercorns and a number of herbs. In wine, rotundone originates mainly from the grape skins of some varieties and is extracted during alcoholic fermentation. The concentrations of rotundone in Shiraz grapes have been shown to vary significantly between vineyards, between vintages for the same vineyard, and between grapevines within a vineyard, and its presence appears to be associated with variations in soil properties, topography, ambient temperature, and vine water status (see soil water).
