A WINE ARABINOGALACTAN-PROTEIN THAT REDUCES HEAT-INDUCED WINE PROTEINHAZE

An arabinogalactan-protein which reduced the heat-induced turbidity of protein in wine was purified from a red wine. The arabinogalactan-pro tein (AGP) was composed of a central 3-linked galactan core carrying, at position 6,6-linked galactan chains which were in turn heavily subs tituted at positions 3 and 4 by terminal arabinofuranose residues and short 5-linked arabinan chains. The protein (13% by weight) was domina ted by serine, alanine, hydroxyproline, and threonine, and also contai ned a relatively high amount of the basic amino acids lysine and argin ine. The molecular weight, estimated by universal calibration, was 210 ,000. Enzymatic removal of the terminal arabinofuranosyl units of the active AGP and subsequent partial shortening of the outer 6-linked gal actan chains did not affect the haze protective activity. Periodate ox idation and then Smith degradation greatly reduced the size of the pol ysaccharide, its amount of protein, and eliminated its absorption at 2 80 nm and its haze protective activity.