Evolution of the crown procyanidins during wine making and aging in bottle

Abstract

Condensed tannins are widely distributed in plant‐derived foods and beverages like grape, red wine, nuts, tea, apples and chocolate in which they contribute to multiple sensorial properties such as flavor, color, and taste (astringency and bitterness). During the wine making process, condensed tannins are extracted from the skins and seeds of the grape and their concentration in red wine are influenced by the grape varieties as well as technical process used. Recently, a condensed tannin sub-family with an unusual skeleton has been reported, and named crown procyanidin. These compounds have a specific structural feature of being cyclic and being composed only of B type inter-flavonoid linkages. All the sub-units of the NMR characterized tetramer are (−)-epicatechin and it presents within its structure a relatively big cavity and composed of four aromatic rings and several phenol functions. The first identification of the tetramer and some pentamers has been report in the red wine. However, recent study showed that these molecules are specifically located in grape skins and there concentration in red wine depends of the grape varieties. 

The goal of this study was to determine the evolution kinetics of crown procyanidins (tetramer and pentamers) during the wine making process as well as during the aging of red wine in bottles. The organoleptic impact of these new tannins sub-family has been also investigated. 

Firstly, the extraction evolution kinetics of crown procyanidins was determined during the wine making of Carbernet Sauvignon grape harvested in Paulliac, Bordeaux. It appears that the crown procyanidins are extracted at the beginning of the maceration and are highly water soluble in contrast of non-cyclic condensed tannins which need alcohol to be extracted. Indeed 70 % of crown procyanidins are extracted during the first 24 hours. Secondly, red wines aged between 2 to 20 years have been obtained from the same winery and sensorial analyses as well as chemical analysis have been performed on an UPLC-UV-QTOF. During red wine aging in bottle, the crown procyanidins concentrations remain stable, whereas the noncyclic condensed tannins decreased with time. In order to understand why the concentration of crown procyanidins remain stable, some oxidisability test has been performed to compare the crown procyanidins and the noncyclic condensed tannins and the crown procyanidins appeared to be more resistant to oxidation than noncyclic condensed tannins.