Total Volatile Acidity in Wines, Exclusive of Sulfur Dioxide: Collaborative Study

Abstract

Abstract Two methods for determining total volatile acidity in wines, exclusive of sulfur dioxide, were collaboratively studied by using a matched pair scheme. Both methods required an alkali titration of a steam distillate of wine. With one method, the titration of the distillate gave total volatile acidity measurements exclusive of sulfur dioxide when mercuric ions were present during distillation (direct-titration method). With the other method, the interferences of free and bound sulfur dioxide were excluded following the alkali titration by titrating their equivalence as acetic acid with iodine (back-titration method). This required additional manipulation of the sample, including 2 extra titrations. The results of the collaborative study showed that although the mean measurements for both methods were close, variability in repeatability and reproducibility was always smaller (both among and within laboratories) for the directtitration method. This method has been adopted as official first action.