The Relationship of pH and Acid in Winemaking

Home winemakers know pH and acid are related when they make wine. Beyond that, the details sometimes get a little fuzzy. Shedding some light on how these important parameters are — and are not — linked to one another may help make better winemaking decisions. There are theoretical considerations from organic chemistry and laboratory analysis, practical effects on the wine, and a range of steps that can be taken if a change in pH or acid is desired. Of the two, I will start with pH. It represents just one thing — the concentration (or “activity”) of free hydrogen ion (H+) in a given solution. “Acid” on the other hand encompasses several different compounds in wine. The pH scale runs from zero at the highly acidic end of the scale to 14 at the highly basic (caustic) end. Pure water has a pH of 7.0, right in the middle. Everything below pH 7 is called acidic and everything above 7 is basic, with 7 referred to as neutral pH. To express the concentration of hydrogen ion on the pH scale,