Determining Free Sulfur Dioxide in Red Wine

Abstract

Apparent equilibrium constants were determined for dissociation of the bisulfite addition compounds of malvidin-3-glucoside and of an extract of anthocyanins from a red wine. Normal methods of determining the free SO₂ content of wines, which require acidification of the sample, give high results because anthocyanin bisulfites are unstable. The true free SO₂ content of red wines can be calculated from the extent to which the natural anthocyanins are decolorized by SO₂.