Contribution of oak wood ageing to the sweet perception of dry wines

Background and Aims Winemakers observe a sensory effect of oak ageing in wines, but the phenomenon has never been fully described. The aim of this study was to determine the influence of the ageing container on the sweetness of dry wines and to evaluate the contribution of oak volatile compounds. Methods and Results Both white and red dry wines were produced in various containers, such as stainless steel and oak tanks, and new and used oak barrels. Sensory analysis (with or without use of nose clip) by a panel of experts showed an increase in sweetness when wine was in contact with wood. Oak volatile compounds (vanillin, β-methyl-γ-octalactone and eugenol) were quantified by gas chromatography-mass spectrometry and then added to the wines to obtain the same concentration in all samples. To determine the contribution of the volatiles to the increase in sweetness, the treatments were tasted again after such an ‘oak aroma’ homogenisation. The ranking of the wines remained unchanged. Conclusion These results demonstrate that the sweet perception of dry wines depends on the nature of the ageing container, and that these oak volatiles are not involved in this phenomenon. Significance of the Study This work confirms an empirical observation and establishes for the first time the sweetening effect of oak ageing, strongly suggesting the existence of sweet non-volatile compounds in oak wood.