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 det ermine the influence of organic acids on the buffering capacity of musts an d wines, aqueous and hydroalcoholic 11% (v/v) model solutions of some organ ic acids of the grape (tartaric, malic, and citric acids) or acids formed d uring 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 acid ic hydroalcoholic solutions. The solutions studied corresponded to only one acid or to equimolar mixtures of two or three acids, the total acid concen tration being 40 mM in each case. In water and for the same acid concentrat ion, it was shown that the buffering capacity due to succinic acid and citr ic acid is equivalent to that of malic acid. Study of mixtures of acids mai nly showed that experimental values of the buffering capacity are lower tha n those calculated for independent acids, suggesting that interactions betw een acids take place in wine.