Polyelectrolyte titration of whisky

Polyelectrolyte titration using a fluorescent indicator was applied to dete rmine the electrolytic charges in 10 whiskies at various pH levels. Tannic acid was also titrated to compare the relation between pH and charge becaus e the polyelectrolytes in whisky were postulated to be polyphenols. mainly tannic acid, which are gradually extracted from a wood cask over the years. Below pH 7, the pH-charge curves for whisky were analogous to those for ta nnic acid, indicating that carboxyl groups in tannic acid were fairly stabl e on maturation of the whisky. The charge of the tannic acid increased with increasing pH, whereas that of whisky had a tendency to level off. The deg ree of leveling off was higher for whiskies with longer maturation. These p henomena are believed to be due to the oxidation of pyrogallol and catechol moieties in tannic acid, which occurs during storage of the whisky. There was a clear tendency for the whiskies with higher prices to have higher cha rges, that is, a higher tannic acid content.