Evaluation of Small Amounts of Flavonoid Phenols in White Wines by Colorimetric Assays

Abstract

For evaluation of flavonoid phenols in the low concentration range in white table wines, four colorimetric assays have been compared: (a) reaction with Folin-Ciocalteu reagent before and after precipitation of flavonoids in HCl-methanal (FC); (b) reaction with vanillin (VAN); (c) reaction with 4-(dimethylamino)-cinnamaldehyde (DAC); and (d) a rapid browning test at 60°C in oxidative medium (POM). There was a highly positive correlation between concentration units obtained by FC, VAN, and DAC, while POM is poorly correlated to concentration units. VAN and, to a lesser extent, FC lead to an overestimation of flavonoid content. DAC displays highest sensitivity and reproducibility. It appears most suitable for appreciation of oxidative aging potential in routine control.