furfural (C5H4O2) is a heterocyclic aldehyde found in many spirits, produced from the breakdown of sugars when heated with acids, as are found in many distillers’ washes. A colorless or pale yellow oily liquid with the aroma of bitter almonds and even caramel or cherry (it is recognizable as a component of vanilla), it slowly turns reddish-brown with oxidation. See oxidation. A heavy molecule with a high boiling point, furfural tends to be found much more in pot-still products than in column-still ones, where it is easy to exclude. Its low volatility means that it is generally not noticeably diminished by barrel aging. In fact, since it can be produced in oak when it is charred or toasted, furfural levels sometimes increase during the aging process, through both concentration and leaching. Toxic in large quantities, furfural has often been one of the compounds blamed for producing hangovers.
“Furfural.” American Chemical Society. https://www.acs.org/content/acs/en/molecule-of-the-week/archive/f/furfural.html (accessed April 21, 2021).“Compound Summary: Furfural.” PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/7362 (accessed February 9, 2021).
Thorpe, T. E. A Dictionary of Applied Chemistry. London: Longmans, Green, 1912–1916.
By: Doug Frost