Aroma characterization of aged cognac spirits: contribution of volatile terpenoid compounds

Grapevine Vitis vinifera L. is a leader perennial crops for the Republic of Georgia, the South Caucasus. This is a region where the first wine making practice was initiated 8.000 years ago (McGovern et al. 2017) and a spot of grape domestication. The country of Georgia holds 525 local and more than 60 breeding varieties – they are preserved in 9 field collections inside the country.The list of recommended wine cultivars contains 34 names, including 27 old autochthonous varieties and covering 94% of the country’s vineyards.

L’appellation d’origine contrôlée “Côtes du Rhône” se caractérise par une très forte implantation du mouvement coopératif. Afin de mieux exploiter le potentiel qualitatif de leurs terroirs, plusieurs coopératives élaborent des “cuvées terroir”, résultat des sélections de vendanges provenant de différents secteurs.

Stilbenes are natural bioactive polyphenols produced by grapevine. Recently, we have reviewed the na- tural presence of these compounds in wines [1]. This study showed that the resveratrol and its glycoside, the piceid, are the most abundant stilbenes in wines. Resveratrol is a well-known stilbene with a wide range of biological activities. Due to its specific structure, resveratrol can be oxidized in wines to form various derivatives including oligomers [2]. In this study, we investigate the resveratrol and piceid transformation in wines.

All techniques usually used to assay proteins was not reliable in vegetable extract due to interferences with the components included in extracts like polyphenols, tanins, pectines, aromatics compounds. Absorbance at 280nm, Kjeldhal assay, Biuret and Lowry methods, Acid Bicinchonique technique and Bradford assay give the results depending on the composition of extract, on the presence or not of detergent and on the raw material (Marchal, 1995). Another difficulty in these extracts for the quantification of proteins comes from the large amount of water included in vegetable and the low concentration of proteins. Thus in red wines, proteins are usually not taken into account due to their low concentration (typically below 10 mgL-1) and to the presence of anthocyanis and polyphenols.

Pre-fermentative skin maceration is a technique used in white wine production to enhance varietal aroma, but it can increase protein concentration, leading to protein instability and haze formation [1]. To prevent protein instability, wine producers typically use fining agents such as bentonite, before wine bottling, which can negatively impact sensory characteristics and produce waste [2,3]. The aim of this study was to understand the impact of alternative techniques such as the application of polysaccharides (k-carrageenan and chitosan) on protein stability and on the wine macromolecular composition.