Influence of storage conditions on the formation of some volatile compounds in white fortified wines (Vins doux naturels) during the aging process

Sweet fortified wines, traditionally aged under strong oxidation conditions, have a characteristic aroma. An experimental study investigated the aging of white sweet fortified wines under various conditions. The development of various molecules, previously identified as characteristic of the aroma of this type of wine, was monitored by analysis. The development of these compounds during accelerated aging was affected by oxidation and the color of the wine. Aging in oak containers, variable storage temperatures, and variable modes of oxidation affect the formation of many of the volatile compounds responsible for the aging aroma of vins doux naturels (fortified wines). Furfural (1), 5-ethoxymethylfurfural (2), and sotolon (3) always reach concentrations above their perception thresholds in wood-aged wines, especially when new oak is used. The isomers of methyl-gamma-octalactone (4 and 5) are reliable indicators of aging in oak. Among the many identifiable volatile phenols, only the vanillin (7) content increases with aging, particularly if the container is made of wood and there is a high degree of oxidation. This molecule frequently reaches and even exceeds its perception threshold. We show here that vanillin and isomers of methyl-gamma-octalactone have a major impact on the aromas of fortified wines.