The American Society of Brewing Chemists defines titratable acidity as, “the number of acidic protons that the organic acid potentially can donate. It is experimentally determined by measuring the amount of sodium hydroxide required to raise the pH to 8.2, where neutralization of the acids occurs” (ASBC Beer-8).
Titratable acidity measurements are used to determine the concentration of acidic compounds in solution, including organic acids and free protons. In contrast, pH measurements can only be used to determine the concentration of free protons in solution and cannot be used to determine the concentration of organic acids. This is important because organic acids are frequently the compounds responsible for providing flavor traits. What does this mean? To put it simply: titratable acidity measurements will generally correlate with taste perception of acidity, while pH measurements will not.
The Brewer Encyclopedia is our attempt to bring our working understanding and definitions for brewing terms to you. It resulted because we found ourselves building a list of useful terms that we could refer back to on short notice. Eventually the list got long enough we figured we'd type it up. Original sources are cited at the end of each entry so that you can refer to them.