Volatile Compounds Involved in the Aroma of Sweet Fortified Wines (Vins Doux Naturels) from Grenache Noir

A typical commercial sample of red Vins Doux Naturels (VDN), Maury 1991, was analyzed by liquid−liquid extraction with dichloromethane followed by chromatographic analysis by GC/FID, GC/MS, and GC/sniffing. GC/sniffing using a DB-Wax and a DB-5 fused silica capillary column revealed five substances having odors corresponding to the aromas of these sweet fortified wines: an enolic lactone, 3-hydroxy-4,5-dimethyl-2(5H)-furanone or sotolon; an acetal, trans-2-methyl-5-hydroxy-1,3-dioxane; and three ethyl esters, 4-carbethoxy-γ-butyrolactone, ethyl 2-hydroxyglutarate, and ethyl pyroglutamate. The last four compounds have been synthesized and their olfactory characteristics checked under the same conditions, which confirmed the odors revealed for the natural compounds except for trans-2-methyl-5-hydroxy-1,3-dioxane, which exhibited no odor. Furthermore, five other sweet fortified wines subjected to different types of oxidative aging were analyzed to quantitatively determine the four identified aroma compounds. The three ethyl esters were found in these wines at different levels increasing with oxidative aging. However, sotolon could not be detected. In addition, other volatile compounds from the six wines were analyzed. The levels of polar ethyl esters and the related lactones, the carbonyl compounds, and their acetals increased in the wines after oxidative aging as well. Keywords: Sweet wine; aroma; oxidative aging; Grenache; Vins Doux Naturels