INFLUENCE OF YEAST STRAIN ON BINDING OF SULPHUR DIOXIDES IN WINES AND ON ITS FORMATION DURING FERMENTATION

The amounts of sulphur dioxide bound by acetaldehyde, pyruvic acid and α‐ketoglutaric acid during fermentation of three grape juices by eight wine yeasts (Saccharomyces sp.) are reported. These constituents accounted for 49–83 % (mean 69) of the measured bound SO2, depending on the yeast strain and juice. the maximum range of concentrations of the binding components for individual wines were 10–48 ppm for acetaldehyde, 9–77 ppm for pyruvic acid and 5–63 ppm for α‐ketoglutaric acid, depending on yeast strain and grape juice. the validity of the calculations was verified by an experiment with SO2 and the three binding compounds in a multicomponent model system. The acetaldehyde content was related to the total SO2 present, which itself was determined by the strain of yeast. SOz bound in the wines after a further SO2 addition was correlated significantly with pyruvic and α‐ketoglutaric acids, but not with acetaldehyde. Certain yeasts produced SO2 during fermentation in grape juice and in synthetic media with defined sulphur sources. More SO2 was produced at pH 3.6 than 3.0 in the absence of added sulphate in grape juice. Sulphate was the best sulphur source for SO2 production in synthetic media, although some yeasts were able to produce smaller amounts of SO2 from l‐cysteine and reduced glutathione. Copyright © 1969 John Wiley & Sons, Ltd