Pectic polysaccharides, arabinogalactan

Dufour and Bayonove (1999a) reported two criteria for polysaccharide discrimination acidity and protein content. Neutral peptic substances (type II arabinogalac-tans and arabinogalactans-proteins) represent 40% of the polysaccharides in wine and acidic pectic polysaccharides, (e.g. homogalacturonans and rhamnogalacturo-nans) account for 20% of them. Because of the difficulty in purifying wine polysaccharides, most of the studies on interactions between wine polysaccharides and aroma compounds have been carried out with exocellular and cell wall mannoproteins (thus mainly glycoproteins) of Saccharomyces (see effect of yeast and derivatives in the next section). 

Glucomannans Mannans Xylans Xyloglucans Pectic polysaccharides Arabinans Arabinogalactans Galactans Galacturonans Rhamnogalacturonans... 

Figure 5.3 Structures and typical structural elements of important pectic polysaccharides (A) arabinogalactan (B) polygalacturonan (C) rhamnogalacturonan (D) arabinan (E) xyloglucan (F) amylose and amylopectin (G) caUose and laricinan.

The common hemiceUulose components of arborescent plants are listed in Table 3. Xylans, arabinogalactans, and pectic substances are common to all while only traces (if at all) of glucomaimans are found in the cell walls of bamboo. Other polysaccharides are found in trace amounts in wood as well as in bark, growing tissues, and other specialized parts of trees. 

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