Pectic substances neutral

Grape polysaccharides resnlt from the breakdown and solnbilization of some of the pectic substances in the skin and flesh cell walls. The terminology describing these componnds may be confusing, as the definition of certain terms (pectins, gums, neutral pectic substances, acid pectic snbstances, etc.) varies from one anthor to another. 

A more recent, clearly preferable classification (Brillouet, 1987 Brillouet et al, 1989) simply divides soluble polysaccharides in must into neutral pectic substances and acid pectic substances, depending on whether or not the molecules contain... 

Pectins can generally be divided into neutral and acidic polymers, but certain structural features are common between the different types of pectic substances. These will be described below. Concerning the general chemistry of carbohydrate types of linkages, the reader can find details on this in general textbooks of chemistry and biochemistry and is for this reason not included. 

Matsuhashi S, Inoue S-1, Hatanaka C (1992) Simultaneous measurement of the galacturonate and neutral sugar contents of pectic substances by an enzymic-HPLC method. Biosci Biotech Biochem 56 1053-1057... 

The FTIR spectra of citrus pectin and wheat straw XRPP (Figure 1) appeared to be similar. Both of the spectra have absorptions at 1740, 1608, 1430, 1360, 1244, 1080, 1060, 1035, 890 and 524 cm. The pectic substances belong to a class of carboxy poly saccharides which differ from neutral polysaccharides, with an intense band in the region 1740 cm l (for salts 1608 cm ) related to vibrations of the carboxyl group... 

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). 

Protopectin is composed of water-insoluble pectic substances, which are fixed to the middle lamella and primary cell walls of plant cells. The neutral sugar side chain of the pectin is attached to the xyloglucan residues, which are bound to the cellulose fibers. The protopectin includes polyvalent such as calcium (Fig. 11.4-8). Protopectin is present in unripe fruits. During the maturation process of fruits or after harvesting, the protopectin is converted to soluble pectin11851. The insolubility of protopectin may be due to the polymerization of the molecule and to the cross-linking with divalent cations11861. 

The rhamnogalacturonan zones of acid pectic substances generally have lateral chains of neutral OSes, connected to carbon 4 of the rhamnose. For this reason, they are known as bristled zones , as opposed to the smooth zones of homogalactur-onan that do not branch off (Figure 3.18). There are two types of lateral chains in the bristled zones arabinogalactans in the majority (AG-II) and arabinans (A). 

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