RT Journal Article
SR Electronic
T1 Charge Properties of Some Grape and Wine Polysaccharide and Polyphenolic Fractions
JF American Journal of Enology and Viticulture
JO Am J Enol Vitic.
FD American Society for Enology and Viticulture
SP 25
OP 30
DO 10.5344/ajev.1996.47.1.25
VO 47
IS 1
A1 A. Vernhet
A1 P. Pellerin
A1 C. Prieur
A1 J. Osmianski
A1 M. Moutounet
YR 1996
UL http://www.ajevonline.org/content/47/1/25.abstract
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.