RT Journal Article SR Electronic T1 Effect of Winery Yeast Lees on Touriga Nacional Red Wine Color and Tannin Evolution JF American Journal of Enology and Viticulture JO Am. J. Enol. Vitic. FD American Society for Enology and Viticulture SP 98 OP 109 DO 10.5344/ajev.2012.11103 VO 64 IS 1 A1 Ana Rodrigues A1 Jorge Manuel Ricardo-Da-Silva A1 Carlos Lucas A1 Olga Laureano YR 2013 UL http://www.ajevonline.org/content/64/1/98.abstract AB Red wine aging on lees is a winemaking practice used to achieve more rounded and less astringent wines. In two different trials, external yeast lees were added to a red wine and their effects on wine color and tannin evolution during aging were studied. Results indicated that the addition of yeast lees did not affect color stabilization during the studied period. Color compounds and condensed tannins were rapidly adsorbed to the yeast lees at the beginning of the experiment. There was a retarding effect on proanthocyanidin polymerization reaction by the addition of yeast lees, leading to the maintenance of low and medium molecular weight tannins in solution. Two different interactions were observed: first, proanthocyanidin adsorption by the yeast lees, primarily ones with the highest polymerization degree, and second, the retarding of proanthocyanidin polymerization, likely by the mannoproteins released by yeast lees. The age of the yeast lees was a factor in mannoprotein release and its effect in wine.