EVOLUTION OF TOASTED AROMAS IN RED WINE DURING BARREL MATURATION

Well known are the woody aromas descriptors characterize wines aged in barrels: smoky, spicy, coco, vanilla, and roasted coffee, and toasted bread. We have known for a good ten years the principal molecules responsible for the odours of spice, smoky and coco. Volatile phenols in particular eugenol yields the smoky, spicy aromas; cis and trans methyl octalactone gives coco, phenol aldehydes, in particular yields vanilla, and vanillin notes. P. Chatonnet (1-3) in the 90’s demonstrated the influence on the formation of these components, essential parameters of the cooperage: oaks botanic origin and geography, modality of merrains drying, burning intensity of staves. In the other hand, the nature of the odourants which are responsible for the roasted coffee notes has remained enigmatic for a long time; in effect, furanic aldehydes, in particular furfural, possess grilled odours but sensory threshold is well below the levels in which we find them in wine. Their olfactory impact is negligible. Recently, works by T.Tominaga et Blanchard (4) showed that key roasted aroma in barrel aged wines is a volatile thiol, extremely odorous, 2-furanemethanethiol (2-FM). This molecule was identified for the first time, since 1926, in roasted coffee (5); it is not surprising that tasters utilize this descriptor to qualify empyreumatic odour in barrel aged wines. 2-FM was equally found in different cooked food, like meat juice, grilled meat, and popcorn where it forms by Maillard reaction between cystine and pentoses at high temperature. The formation of 2-FM in wine is not totally elucidated. In white barrel aged wines, its production occurs over the course of the alcoholic fermentation, by bio-transformation of furfural given by the wood, by yeast sulfur metabolism (6). In the red wines, 2-FM and the roasted character, appear relatively quick after being in a new barrel. We will report on different observation on key parameter needed for 2-FM evolution over the course of red wine barrel aging.