Depletion Of Vine-Shoots Phenolic Composicion After Being Used As An Enological Tool For Wine Differentiation

Abstract

Pruning vine-shoots are a viticulture waste that have been traditionally poorly exploited in relation to its chemical minority composition related to phenolic and volatile compounds. In this line, toasted vine-shoots supposes a proposal of enological tool to use to modulate the chemical and sensorial profile of wines. From a phenolic point of view, when vine-shoots are used during winemaking mainly influence to increase the flavanols and stilbenes content, mostly trans-resveratrol, as also an increasing in the sweet tannins and decreasing the green character and total anthocyanins, changing the violet for garnet colour.
Along with the already proven release of compounds from the vine-shoots to wines elaborates with them, the transfer of some of them that are present in wines to vine-shoots must be considered. For this, the aim of this work was to evaluate the depletion in terms of transfer of phenolic compounds from the wine to vine-shoots that were used during vinification. For which, vine-shoots were analysed before and after having been in contact with the wine. To compare the effect on the type of wine, two wines from Tempranillo and Cabernet Sauvignon were considered, to which toasted vine-shoots of their corresponding varieties were added after malolactic fermentation in a dose of 24 g/L. The analysis in terms of phenolic composition was development by HPLC-DAD.

The results revealed that different patterns were observed for families. As expected, there was a clear transfer of anthocyanins from the wine to vine-shoots, ranging between 3.3 and 3.5 g/Kg for Tempranillo and Cabernet-Sauvignon, which resulted in a loss of 25 to 27% in wines from the respective varieties. The same behaviour was observed for flavonols group, whose content was among 0.29 and 0.25 g/Kg for Tempranillo and Cabernet-Sauvignon vine-shoots, being its decrease in wines between 31 to 25%, respectively. In contrast, flavanols, phenolic acids and stilbenes showed an average increase of 14%, 8% and 57%, showing trans-resveratrol the greatest increase.
These results show the different transfer of phenolic compounds from the wine to vine-shoos. This would suppose that, after being used during winemaking, vine-shoos could be considered for a second use, given their remaining potential. 

Acknowledgments: This study was supported by USARVID019 Project (Ref.: IDI-20190844), financed by Pago de la Jaraba winery (Albacete, Spain) through the FEDER and CDTI entities.