Background and Aims: Rotundone, a potent aroma compound responsible for peppery aroma and flavour in Shiraz, was detected recently in Vitis vinifera L. cv. Duras wines. In 2011 and 2012, two separate experiments were carried out to determine the effect of ripeness and viticultural techniques on rotundone concentration in Duras wine. Methods and Results: Rotundone was measured in wines prepared by microvinification techniques (1 L Erlenmeyer). Accumulation of this compound in wines depended on vintage conditions and the degree of ripening, such that a higher concentration of rotundone was reached 44 days after mid-veraison. Application of exogenous jasmonic acid and grape thinning did not significantly affect rotundone concentration, whereas leaf removal strongly reduced rotundone concentration. Wine from the irrigated treatment had a higher concentration of rotundone, and in most cases, vine water status over the veraison-harvest period was identified as a key variable that was well correlated with observed intraplot variability. Conclusions: These findings confirm that some common viticultural practices can be used to manipulate the peppery character in red wine. Significance of the Study: Our results may assist grape growers to produce Duras, Shiraz and other cultivars where rotundone makes an important contribution to wine aroma.

Experiments were carried out on Grenache, Carignan and Fer grapes in order to characterize the changes in nitrogen content of the musts, conventional enological parameters and aroma compounds of the wines induced by pre-fermentation heating of the grapes followed by alcoholic fermentation in liquid phase or in solid phase. In comparison to a standard vinification, we showed that a two-hour heat treatment at 70 °C induced a significant loss in several grape-derived aroma compounds (terpenols, norisoprenoids and some phenols) associated with an increase in α-terpineol, guaiacol and 2,6-dimethoxyphenol, which suggests thermal degradation. A significant increase in most of the ethyl esters, in acetates and in fatty acids were observed in wines fermented in liquid phase, together with a decrease in fusel alcohols. The substantial modification in the amino acid composition of the must seems to be a crucial element for the understanding of these changes.

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Background and Aims: Rotundone is responsible for peppery aroma in wine. This note is not appreciated by all consumers, which indicates that rotundone might be considered as a taint above a certain concentration. The current study aimed at determining a consumer rejection threshold for rotundone in Duras red wine. Methods and Results: Consumers (n = 62) received pairs of samples consisting of a base wine and the base wine spiked with an ascending concentration of rotundone and were asked to indicate which sample they preferred. Anosmic respondents detected through triangle tests represented 31% of the panellists. For these panellists, the wine spiked at the lowest concentration was significantly rejected suggesting that rotundone might induce a trigeminal sensation and/or is involved in molecular mechanisms of flavour reduction. For remaining panellists, we were not able to determine any consumer rejection threshold. We identified three clusters of consumer profiles. The first cluster preferred a moderate concentration of rotundone and rejected a high concentration. The second cluster, mainly composed of young consumers, preferred the Control. The last group appreciated peppery wines especially at high concentration. Conclusions: The response of consumers to rotundone is complex, and peppery notes are perceived positively or in a neutral manner by most consumers with the exception of young panellists. Significance of the Study: Our results may assist grape growers producing Duras and other cultivars, where rotundone makes a sensory contribution, to adapt their products to consumer profiles. They also open new fields of investigation into mechanisms involved in specific anosmia to rotundone.

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