PT  - JOURNAL ARTICLE
AU  - A. Vernhet
AU  - P. Pellerin
AU  - C. Prieur
AU  - J. Osmianski
AU  - M. Moutounet
TI  - Charge Properties of Some Grape and Wine Polysaccharide and Polyphenolic Fractions
AID  - 10.5344/ajev.1996.47.1.25
DP  - 1996 Jan 01
TA  - American Journal of Enology and Viticulture
PG  - 25--30
VI  - 47
IP  - 1
4099  - http://www.ajevonline.org/content/47/1/25.short
4100  - http://www.ajevonline.org/content/47/1/25.full
SO  - Am J Enol Vitic.1996 Jan 01; 47
AB  - Charge densities of the major wine polysaccharides and of grape seed and wine polyphenols have been determined with a method developed by Mütek (Germany), relying on titration with a counter-charged polyelectrolyte associated to streaming potential measurements. Charge densities were determined in a model hydroalcoholic solution at pH 3.5 and in 10 mM KNO3 solutions, from pH 2 to 9. The polysaccharides tested — yeast mannoproteins, grape arabinogalactan-proteins (AGPs), and rhamnogalacturonan RG-II — carried negative charges in the wine pH range. The net charge density of yeast mannoproteins was shown to be related to their phosphorus content and to be pH-independent in the range tested (2 to 9). Absolute charge densities of AGPs and RG-II were related to the dissociation of the carboxylic functions of their uronic acids and increased dramatically in the pH range 2 to 5. Polyphenolic fractions, including native tannins isolated from grape seeds and polyphenolic fractions recovered from wine, carried no charges or negligible charges at pH 3.5. As a consequence, wine polysaccharides may establish electrostatic and ionic interactions, but such interactions will play little, if any, in the association of polyphenols with other components.