Abstract
<p>This work studied how different grape maturity levels and cluster treatments affect the color and phenolic composition of Grenache wines. Specifically, five treatments were undertaken at a microvinification scale for three maturity levels : Control (destemmed and crushed grapes), Whole Berry, Whole Cluster, Crushed Cluster and Submerged Cap. The first three treatments were also reproduced with large-scale wine fermentation in oak barrels but only with well-ripened grapes. The results indicated that the total polyphenol index (TPI), anthocyanin and proanthocyanidin concentrations, as well as the mean degree of polymerization were higher in all the treatments when the grapes were riper. Submerged Cap generated maximum color and polyphenolic extraction at the three maturity levels. Whole Berry wines were the most similar to the controls. The presence of stems (Crushed Cluster and Whole Cluster treatments) produced wines with a significantly higher pH at all maturity levels and with lower color intensity when the grapes were less ripe. The presence of stems also significantly increased the TPI in almost all cases.</p>
Highlights
The quality of red wines is highly determined by the composition of phenolic compounds
The results indicated that the total polyphenol index (TPI), anthocyanin and proanthocyanidin concentrations, as well as the mean degree of polymerization were higher in all the treatments when the grapes were riper
Anthocyanins are only present in grape skins of most grape cultivars, with the exception of teinturier varieties, whereas proanthocyanidins are present in skins, seeds, and stems (Ribereau-Gayon et al, 2000)
Summary
The quality of red wines is highly determined by the composition of phenolic compounds. Some of their sensory attributes, such as color, body and astringency, are mainly associated with the composition of anthocyanins and proanthocyanidins (Gawel, 1998; Vidal et al, 2003). Skin proanthocyanidins have a higher mean degree of polymerization (mDP) than seed proanthocyanidins but the polymerization degree of stem proanthocyanidins is a subject of controversy (Souquet et al, 2000; Vivas et al, 2004; del Llaudy et al, 2008). A greater degree of polymerization and a higher percentage of galloylation cause a greater perception of astringency (Vidal et al, 2004)
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