Structural Modification of Wine Arabinogalactans during Aging on Lees

Abstract

The effect of aging red wine on lees is under development as a winemaking technique. During aging on lees, yeast components, in particular polysaccharides, are released to the wine by autolysis. Evolution of polysaccharides originating from the cell walls of grape berry (arabinans, AGPs, RG-II, and RG-I) or released during fermentation or after autolysis of yeasts (mannoproteins) was followed during aging on lees of a red wine from Madiran. The analyses of composition and structure of the macromolecular fraction of the wines aged on lees with or without stirring showed degradation of polysaccharides from grape. This modification consisted of a 75% dearabinosylation of arabinogalactan-proteins (AGPs) and a total degradation of the pectic arabinans. Partial degradation of the ß-(1→3)-galactan chains of the backbone of the AGP was demonstrated by structural analysis. The arabinose to galactose molar ratio of AGPs decreased from 0.8 for a control wine to 0.3 for a wine aged on lees. The stirring of lees during the aging of wine allowed a slight increase of mannoprotein content. This release may be sufficient to alter organoleptic qualities of wines aged on lees over time.