Total acidity: proton equivalence of the amount of organic acid anions present in a wine. It is the number
of protons (also called hydrogen ions, or simply H+
) that the organic acids (lactic, succinic, citric, acetic,
and sulfurous acids) would contain if they were undissociated. It is calculated by measuring the acid anion
concentration (by spectrometry or chromatography), expressing them as molar quantities (number of
molecules per volume), and then multiplying by the number of protons that would result from complete
dissociation.
Titratable acidity: number of protons recovered during a titration with a strong base to a specified
endpoint. It can also be expressed as a molar quantity. Many people use titratable acidity and total acidity
as synonyms, but they are not. The titratable acidity is always less than the total acidity, because not all of
the hydrogen ions expected from the acids are found during the determination of titratable acidity.
However, titratable acidity is easier to measure.
pH: logarithm of the concentration of free protons, expressed with a positive sign