7 Carbohydrates 245
Fig. 7.10Hypothetical structure of RG-II. The figure shows the four oligoglycosidic side chains
A–D whose residues are numbered according to the model sequence. Reprinted from Pellerin
et al. (1996), with permission from Elsevier
As shown in Fig. 7.10, RG-II contains 12 different glycosidic residues such as
apiose, arabinose, galactose, 2-O-methyl-L-fucose, 2-O-methyl-D-xylose, 3-deoxy-
D-manno-octulosic acid, 3-deoxy-D-lyxo-heptulosaric acid, and aceric acid among
others, the main chain being formed by galacturonic acids linked at -(1,4) positions
(Boulet et al. 2007). It constitutes the 19% of total polysaccharides in wine (Vidal
et al. 2003). This carbohydrate can lead to the formation of precipitates and haze
due to their possible electrostatic and ionic interactions with other wine constituents
(Pellerin et al. 1996). RG-I is also present in wines although it stands only for the 4%
of total polysaccharides (Vidal et al.2003). This carbohydrate is mainly constituted
by rhamnose and galacturonic acid among others and it has been found to be linked
with xyloglucans.
AGPs have been found to represent more than 40% of total red wine polysaccha-
rides. They are mainly constituted by glycosidic residues of arabinose, galactose
and glucuronic acid although other monosaccharides such as rhamnose, glucose