CHARACTERIZATION OF 2 ARABINOGALACTAN-PROTEINS FROM RED WINE

Two weakly acidic arabinogalactan-proteins (AGPs) were recovered from a red wine by ethanol precipitation, ion-exchange, affinity and size-exclusion chromatography. They represented, respectively, 4.3 and 5.2% of the total alcohol-precipitable colloids. The more acidic arabinogalactan had higher molecular weight, uronic acid and rhamnose contents and higher arabinose/galactose ratio. Both AGPs had similar amino acid compositions. Linkage studies were performed on native and enzymatically dearabinosylated AGPs. Wine arabinogalactans were built of a 3-linked galactan core cross-linked at position 6, with short 6-linked galactan branches heavily substituted by arabinose at positions 3 and 4. Uronic acids were identified as being mainly galacturonic acid, indicating that wine AGPs might derive from native grape pectins.