Solution for the determination of reductones in wine.
Free SO2 determination does not take into account reductones in wines. Reductones are substances that bind sulphite, such as polyphenols (mainly tannins), acetaldehyde and ascorbic acid (vitamin C). The average reductone content of wine is assumed to be 5 mg/l, 10 mg/l or 30 mg/l in white, rosé or red wine, respectively. The free SO2 (in mg/l) is thus calculated by subtracting 5, 10 or 30 mg/l of reductones from the measured SO2 value. However, this is only an estimate.
To determine the actual value you need Glyoxal. This product gives a more accurate indication of the reductone content of the wine in mg/l.