WHICH TERROIR-RELATED FACTORS INFLUENCE THE MOST VOLATILE COMPOUND PRODUCTION IN COGNAC BASE WINE?

Abstract

Cognac is a famous spirit produced in southwest France in the region of the eponymous town from wines mainly from Vitis vinifera cv. Ugni blanc. This variety gives very acidic and poorly aromatic base wines for distillation which are produced according to a very specific procedure. Grapes are picked at low sugar concentrations ranging 13-21 °Brix and musts with high turbidity (>500 NTU) are fermented without sulphite addition [1]. Fermentative aromas, as esters and higher alcohols, are currently the main quality markers considered in Cognac spirits. Hence it is important to better understand the effect of potential influential factors on the production of these compounds as well as on their precursors in berries. This communication deals with the study of the impact of various terroir components among maturity, vine rootstocks, water and nitrogen status that can influence grape and corresponding wine composition. All experiments used Ugni blanc grapes and were conducted in commercial vineyards in the Cognac region as well as in the GreffAdapt plot (13 rootstocks selected) [2]. Fermentations were performed at laboratory scale in triplicate similar to Cognac base wine elaboration under harvest-like conditions and standardized conditions, where sugars and YAN were all corrected to the same values [3]. Berry composition at harvest, including detailed amino acid profile, and wine fermentative aromas, such as higher alcohols and esters, were determined. All the parameters tested here could be ranked from the most influential to the least on ester concentrations. Under harvest-like conditions, nitrogen status was found to be the most influential followed by maturity level and finally water status, which was the least impactful parameter despite a very warm and dry 2022 grape-growing season. Higher alcohol acetates were about twice higher in the high nitrogen-status vines (+ 30 mg/L of YAN) compared to the control. Under standardized conditions, maturity was found the most impactful although the initial differences in must sugars and nitrogenous compounds were smoothed, and nitrogen status was the least. Indeed, fatty acid ethyl esters differed considerably depending on maturity and their concentrations were the lowest when grapes were picked around 13-15 °Brix compared to the other two more advanced maturities. These findings highlight the importance of maturity as a key parameter for growers to take into consideration for Cognac production.