Study of the contribution of the major organic acids of wine to the buffering capacity of wine in model solutions

Tartaric acid and malic acid are known to represent up to 90% of the acids present in musts and wines which have not undergone malolactic fermentation and thus are the major acids contributing to wine acidity. In order to determine the influence of organic acids on the buffering capacity of musts and wines, aqueous and hydroalcoholic 11% (v/v) model solutions of some organic acids of the grape (tartaric, malic, and citric acids) or acids formed during primary fermentation (succinic acid) were used. Buffering capacities were determined using NaOH aqueous solutions for the study of aqueous acid solutions and hydroalcoholic 11% (v/v) NaOH solutions for the study of acidic hydroalcoholic solutions. The solutions studied corresponded to only one acid or to equimolar mixtures of two or three acids, the total acid concentration being 40 mM in each case. In water and for the same acid concentration, it was shown that the buffering capacity due to succinic acid and citric acid is equivalent to that of malic acid. Study of mixtures of acids mainly showed that experimental values of the buffering capacity are lower than those calculated for independent acids, suggesting that interactions between acids take place in wine.