Fusel alcohol

Fusel alcohols or fuselol, also sometimes called fusel oils in Europe, are mixtures of several alcohols (chiefly amyl alcohol) produced as a by-product of alcoholic fermentation.[1] The word Fusel [ˈfuːzl̩] is German for "bad liquor".[2]

Whether fusel alcohol contributes to hangover symptoms is a matter of scientific debate. A Japanese study in 2003 concluded: "the fusel oil in whisky had no effect on the ethanol-induced emetic response" in the Asian house shrew. Additionally, consumption of fusel oils with ethanol suppressed subjects' subsequent taste aversion to alcohol, which suggested subjects' hangover symptoms were lessened, according to the journal.[3]

Usage

Fusel oil and fusel-oil acetates are used in the lacquer industry as high boiling point solvents.[4]

Classification

Hazardous alcohols
  • Methanol (methyl alcohol), while poisonous (LD50 5628 mg/kg, oral, rat[5]), has a much weaker sedative effect than ethanol.
  • Isopropanol (isopropyl alcohol), oxidized to form acetone by alcohol dehydrogenase in the liver, has occasionally been abused by alcoholics, leading to a range of adverse health effects.[6][7]

Congeners

Excessive concentrations of some alcohols other than ethanol may cause off-flavors, sometimes described as "spicy", "hot", or "solvent-like". Some beverages, such as rum, whisky (especially bourbon), incompletely rectified vodka (e.g. Siwucha), and traditional ales and ciders, are expected to have relatively high concentrations of non-hazardous alcohols as part of their flavor profile. However, in other beverages, such as Korn, vodka, and lagers, the presence of alcohols other than ethanol is considered a fault.[8]

The compounds involved are chiefly:[9]

  • 2-methyl-1-butanol - sometimes called "active" amyl alcohol
  • isoamyl alcohol (isopentanol)
  • isobutyl alcohol - one of the least toxic of the butanols.
  • n-propyl alcohol

Distillation

During distillation, fusel alcohols are concentrated in the feints or "tails" at the end of the distillation run. They have an oily consistency, which is noticeable to the distiller, hence the other name "fusel oil". If desired, these heavier alcohols can be almost completely separated in a reflux still. Freeze distillation, on the other hand, does not remove fusel alcohols.

Fusel alcohols are formed when fermentation occurs:

  • at higher temperatures
  • at lower pH
  • when yeast activity is limited by low nitrogen content
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See also

References
  1. "Fusel oil | Definition of fusel oil in English by Oxford Dictionaries".
  2. Hazelwood, Lucie A.; Daran, Jean-Marc; van Maris, Antonius J. A.; Pronk, Jack T.; Dickinson, J. Richard (2008). "The Ehrlich pathway for fusel alcohol production: a century of research on Saccharomyces cerevisiae metabolism". Appl. Environ. Microbiol. 74 (8): 2259–66. doi:10.1128/AEM.02625-07. PMC 2293160. PMID 18281432.
  3. Hori H, Fujii W, Hatanaka Y, Suwa Y (Aug 27, 2003). "Effects of fusel oil on animal hangover models". Alcohol Clin Exp Res. 27 (8 Suppl): 37S–41S. doi:10.1097/01.ALC.0000078828.49740.48. PMID 12960505.
  4. Kenyon, Richard L.; Inskeep, Gordon C.; Gillette, Leslie; Price, J. Frank (1950). "Amyl Compounds from Pentane". Industrial & Engineering Chemistry. 42 (12): 2388–2401. doi:10.1021/ie50492a004.
  5. "ChemIDplus Advanced - Chemical information with searchable synonyms, structures, and formulas".
  6. Wiernikowski A, Piekoszewski W, Krzyzanowska-Kierepka E, Gomułka E (1997). "Acute oral poisoning with isopropyl alcohol in alcoholics". Przeglad Lekarski. 54 (6): 459–63. PMID 9333902.
  7. Mańkowski W, Klimaszyk D, Krupiński B (2000). "How to differentiate acute isopropanol poisoning from ethanol intoxication? -- a case report". Przeglad Lekarski. 57 (10): 588–90. PMID 11199895.
  8. Aroma of Beer, Wine and Distilled Alcoholic Beverages
  9. MERCK INDEX (10th ed.). 1983.
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