Isobutanol

An aliphatic alcohol with a mild, sweet alcoholic odour; isobutyl alcohol and methyl propanol are synonyms. Fermentation in alcoholic beverages — wines, beer, and cider — produces it as an aroma compound. In balanced amounts it rounds out the fermentation bouquet; at high concentrations it contributes harsh, solvent-like notes that mark stressed or faulty fermentations. Distillers monitor higher alcohols like isobutanol because they shape both flavour and the heads fractions of spirits. Its sweet note is pleasant in trace amounts but harsh when fermentation runs hot.