Factors affecting the formation of fusel alcohols during fermentation.

Van Gheluwe, G., Chen, E. and Valyi, Z.

Abstract
Alcoholism has been traditionally connected with only the amount of ethanol present in the beverages. In recent years, there have been attempts to look more closely at the congener content of the beverages since these congeners are sometimes more physiologically active than ethanol itself. Fusel alcohol formation is a normal activity of all yeast fermentations and its concentrations in alcoholic beverages showed a wide range between 2200 and 0 ppm. Fusel alcohols are mainly formed during the first 60% of ale fermentation resulting in hyperbolic curves for their formation. For lager fermentations, the curves showed a sigmoidal shape. Ale fermentations produce larger quantities of fusel alcohols than lager fermentations. The temperature of fermentation is important with higher temperatures producing higher quantities of fusel alcohols. The shape of the fermenter has an important influence on the formation of fusel alcohols. Deep fermentations are effective in reducing the amount of fusel alcohols. Large capacity fermenters are also effective in producing lower fusel alcohol levels. High levels of amino acids and high sugar adjunct levels are effective in producing higher levels of fusel alcohols. Higher than normal yeast rates produce more fusel alcohols; isoamyl alcohol in particular is increased by 80% for a four-fold increase in pitching rate.
Keywords: ale beer fermentation fermenter fusel alcohol lager spirits temperature wine yeast