Changes in Volatile Sulfur Compounds of Whisky During Aging

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Abstract
Volatile sulfur compounds of malt whiskies were analyzed using a gas chromatograph equipped with a flame photometric detector by direct injection and solvent extraction methods. Sulfur compounds identified by coupled gas chromatography‐mass spectrometry and by matching GC retention times were dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, 3‐(methylthio)propanal, 3‐(methylthio)propanol, 3‐(methylthio)propyl acetate, ethyl 3‐(methylthio)‐propanoate, dihydro‐2‐methyl‐3(2H)‐thiophenone, 2‐thiophene‐carboxyaldehyde, 5‐methyl‐2‐thiophenecarboxaldehyde, benzothiophene and benzothiazole. Quantitative changes in these volatile sulfur compounds were studied by analyzing 48 aged and unaged malt whiskies by these methods. Dimethyl sulfide, 3‐(methylthio)propyl acetate, dihydro‐2‐methyl‐3(2H)‐thiophenone and ethyl 3‐(methylthio)propanoate decreased rapidly during aging and disappeared within three years. Dimethyl disulfide decreased gradually during aging. Dimethyl disulfide proved to be formed during distillation by the action of copper.