The most prevalent volatile sulfur compound generally found in beer in the highest concentration is sulfur dioxide. It reacts with carbonyl compounds and for this reason is found primarily in bound form in beer. Sulfur dioxide is a metabolic product of yeast and in beer is in its active form. In many countries, sulfur dioxide is added to beer as a preservative in order to increase flavor stability. According to the regulations governing additives in Germany dating to 29 January 1998, the maximum SO2 content permissible in beer is 20 mg/l (50 mg/l for barrel, cask, keg-conditioned beer). According to EU no. 1169/2011, supplements of sulfur dioxide or sulfites must be declared in concentrations above 10 mg/kg or 10 mg/l as SO2.
Determination of total SO2 content (bound and free) in beer and juices
This method is suitable for beer and other beverages.
Bound sulfur dioxide in beer is liberated through the addition of acid and subsequent heating. Under a stream of nitrogen gas, the sulfur dioxide is transferred into a receiver containing hydrogen peroxide, and the sulfuric acid thus created is titrated with sodium hydroxide.