Volatile Acidity

Abstract

The total acidity of a wine is the result of the contribution of nonvolatile or fixed acids such as malic and tartaric plus those acids separated by steam volatilization. A measure of volatile acidity is used routinely as an indicator of wine spoilage (Table 11.1). Although generally interpreted as acetic acid content (in g/L), a traditional volatile acid analysis includes all those steam-distillable acids present in the wine. Thus, significant contributions to volatile acidity (by steam distribution) may be made by carbon dioxide (as carbonic acid); sulfur dioxide (as sulfurous acid); and, to a lesser extent, lactic, formic, butyric, and propionic acids. In addition, sorbic acid (added to wine as potassium sorbate), used as a fungal inhibitor, is also steam-distillable and should be taken into consideration when appropriate. The contributions of CO₂, SO₂, and sorbic acid interferences are discussed in Chapter 20 (Volatile Acidity).