Changes in the buffering capacity of model solutions of 40 mM tartaric or malic acids in relation to amino acids

The contribution of some amino acids (i.e., arginine, proline, serine, alan ine, threonine) to the buffering capacity of wine using model solutions is established. Although amino acids have no buffering capacities at the pH of wine (2.9 to 4.0), they increase the buffering capacity of a 40 mM tartari c acid solution, even at concentrations found in champagne wines. In contra st, when they are added to a 40 mM malic acid solution, they induce no chan ges in the buffering capacity. It appears that the changes in the buffering capacity depend on the nature of the amino acid used, its concentration, a nd the medium used. For a 40-mM tartaric acid solution, additions of 400 mg /L of each amino acid increase the buffering capacity from 21% in water to 36.8% in an hydroalcoholic medium (11%, v/v).