A winery-scale trial of the use of antimicrobial plant phenolic extracts as preservatives during wine ageing in barrels'

Antimicrobial plant extracts rich in polyphenols have recently been proposed as a total or partial alternative to sulfites during winemaking. This paper reports a first winery-scale trial of the addition of antimicrobial plant extracts during wine ageing in wood. Before being distributed in oak barrels, a Verdejo wine was treated with either a SO2 regular dose (160 mg/L). or with a SO2 half-dose (80 mg/L), together with two phenolic-rich extracts from eucalyptus leaves and almond skins (100 mg/L). Some of the wine was also stored in a stainless steel tank for comparison. After 6 months of ageing, the wine treated with the phenolic extracts remained microbiologically stable and showed correct enological parameters. Also, the volatile and phenolic composition of the wine was specifically determined to ascertain whether the addition of these phenolic extracts would affect the organoleptic properties of the wine. Although the addition of both eucalyptus and almond extracts led to statistically significant changes (p < 0.05) in the concentration of several esters, C13 norisoprenoids, volatile phenols and furanic compounds in the wine, only the concentration of some of these compounds was higher than their odor threshold. With regard to phenolics, addition of both extracts did not significantly modify their content, except for a lower content of hydroxycinnamic acids and esters and flavan-3-ols, which predicts minor changes in wine astringency. As seen from a PCA analysis of all volatile and phenolic data, wines were mainly differentiated by the ageing process itself, by the addition of extracts, and even by the barrel used. Finally, a triangle test showed no significant differences in the global sensory appreciation between wines treated and not treated with the antimicrobial phenolic extracts. These results demonstrated the potential applicability of phenolic extracts as a partial alternative to sulfur dioxide during the ageing of white wines in oak barrels. (C) 2013 Elsevier Ltd. All rights reserved.