fusel oil A mixture of organic acids, higher alcohols (propyl, butyl, and amyl), aldehydes, and esters, known collectively as congeners, produced in alcoholic fermentation.

It is present in low concentration in wines and beer, and in high concentration in pot‐still spirit. On maturation of the liquor fusel oil changes and imparts the special flavour to the spirit. Many of the symptoms of hangover can be attributed to fusel oil in alcoholic beverages.

fusel oil Poisonous, clear, colourless liquid with a disagreeable smell. It consists of a mixture of amyl alcohols, obtained as a by-product of the fermentation of plant materials containing sugar and starch. It is used as a solvent for waxes, resins, fats and oils, and in the manufacture of explosives.