CLUSTER SUN EXPOSURE AND QUERCETIN IN PINOT-NOIR GRAPES AND WINE

Anthocyanin and flavonol content of disks of sun-exposed Pinot noir(Vi tis vinifera L.) berry skin were compared to disks from shaded berries from the same clusters. Anthocyanin content was not affected by sun e xposure, but quercetin glycoside concentration of sun-exposed disks wa s 1.46 mu g mm(-2) for the sun-exposed disks compared to 0.14 mu g mm( -2) for the shaded. Wines were made from Pinot noir clusters from a si ngle vineyard block from three different sun exposure levels: shaded, moderately exposed and highly exposed. The concentration of quercetin glycosides in wine was 4.5, 14.8, and 33.7 mg L(-1) in the shaded, mod erate and highly exposed treatments, respectively. The level of querce tin aglycone also increased with sun exposure. Cluster sun exposure ap pears to be the primary factor determining quercetin levels in grapes and wine. Wines from highly and moderately exposed cluster positions h ad higher total anthocyanin levels than those from shaded clusters, bu t wines from highly exposed clusters had 40% greater polymeric anthocy anins than the other two treatments. Caftaric acid, catechin, and epic atechin concentrations in wine were inversely related to cluster sun e xposure. The low levels of caftaric acid in wines from sun-exposed clu sters appeared to be related to hydrolysis of the tartaric ester, with wines from highly sun-exposed clusters having 50% more caffeic acid t han moderate and 130% more than shaded clusters. Caffeic acid was not present in fruit samples. It is possible that the increase in polymeri c anthocyanins in wines from sun-exposed clusters is directly related to quercetin levels. High wine quercetin levels may increase the rate of polymerization with potential stability and quality implications.