Chemical and sensory evaluation of wine matured in oak barrel: effect of oak species involved and toasting process

The effect of toasting method and forest origin on volatile compounds and ellagitannin concentration extracted into Merlot wine during 1-year barrel maturation is described. Sensory analysis concerning vanilla, spicy, overall woody, astringency, bitterness and sweetness is conducted in parallel. The study is realized in two different experimental designs having only a common parameter, the wine. For the first one, common toasting methods (light, medium) and specific ones (medium toast with watering, medium plus toast, medium plus toast with watering, medium toast with toasted head and Noisette) are chosen. For the second one, the oak from which barrels are made is sourced from Center, Limousin, Allier and Colbert forests in France, from Pennsylvania forest in America, and from Slavonia forest in East Europe. Wine with different characteristics is obtained from the same wine in relation to forest origin and toasting process. Watering process during toasting enhances furanic compounds vanillin and oak lactones extraction, whereas toasting barrel head pieces may lead to eugenol and ellagitannin degradation. Wine in light toast barrel is perceived as less sweet, bitter and more astringent. Ellagitannin concentration is closely correlated to astringency, reflecting the relationship between them, R = 0.599, p < 0.001. Forest origin induces important changes; wine in American barrels is differentiated from those in Slavonia and French barrels. Ellagitannin concentration in barrels from Slavonia is halfway between French and American, and ellagitannin concentration is related linearly to astringency intensity (R = 0.811, p < 0.001). Wine aged in Slavonia showed characteristics similar and intermediate to those of the same wine aged in French and American oak woods, suggesting that they are suitable for barrel production of quality wine.