On-vine grape drying combined with irrigation allows to produce red wines with enhanced phenolic and rotundone concentrations

Can a certain concentration of rotundone be undesirable in Duras red wine? A study to estimate a consumer rejection threshold for the pepper aroma compound

“…Rotundone was reported in grape leaves and stems (Capone et al ) and more recently in Shiraz flower caps at pre‐veraison (Zhang et al ). The compound does not appear to be translocated through the phloem tissues, and the hypothesis of an in situ production is more likely (Geffroy et al , Zhang et al ). Viticultural and environmental factors have a substantial impact on rotundone concentration in grape berries and in finished wines.…”

“…It is enhanced by irrigation and lowered by leaf removal in the bunch zone (Geffroy et al ). The spraying of 1‐naphthaleneacetic acid, a plant growth regulator (Davies et al ), and the implementation of a viticultural system combining irrigation and on‐vine grape drying with cutting of the fruit bearing cane (Geffroy et al ) were successfully tested to enhance rotundone in vineyard.…”

“…Duras is one the most planted red grape cultivars in the Protected Designation of Origin Gaillac in the south‐west of France. As this grape cultivar is known to be a regular rotundone producer with a final concentration in wine, in most cases, over its detection threshold (Geffroy et al , , , ), the base wine spiked with several concentration values of rotundone was made following a viticultural and oenological process conceived to minimise rotundone and therefore having a negligible concentration of this compound in the finished wine. A questionnaire was used to assess whether there are any differences in preference for rotundone across the variables of demographic and level of knowledge.…”

Fortification and Elevated Alcohol Concentration Affect the Concentration of Rotundone and Volatiles in Vitis vinifera cv. Shiraz Wine

“…Rotundone is responsible for the attractive "pepper" character in grape berries and wine, and is especially important for cool-climate Shiraz (Syrah) [6][7][8]. It is possible to manipulate the concentration of this compound in wine by increasing rotundone production in grape berries [8][9][10][11][12][13][14][15][16][17][18][19]. Approximately 10% of the rotundone in grape skins is extracted into the grape berries during fermentation, regardless of starting concentration, so any manipulation that increases the amount of rotundone in grapes will be reflected by an increase in wine.…”

“…These factors explain how lower bunch zone air temperature, lower berry surface temperature, less direct solar exposure and higher precipitation are associated with elevated rotundone production [8,10,16]. Higher irrigation together with on-vine drying has been proven as an effective viticultural technique to improve rotundone concentration in the resultant wine [11].…”