Editing Whisky (section)

===Flavours from distillation===
The flavouring of whisky is partially determined by the presence of [[Congener (alcohol)|congeners]] and [[fusel oil]]s. Fusel oils are higher alcohols than [[ethanol]], are mildly [[toxic]], and have a strong, disagreeable smell and taste. An excess of fusel oils in whisky is considered a defect. A variety of methods are employed in the distillation process to remove unwanted fusel oils.  Traditionally, American distillers focused on secondary filtration using [[charcoal]], [[gravel]], [[sand]], or [[linen]] to remove undesired distillates.

[[Acetal]]s are rapidly formed in distillates and a great many are found in distilled beverages, the most prominent being [[acetaldehyde]] diethyl acetal ([[1,1-diethoxyethane]]). Among whiskies the highest levels are associated with malt whisky.<ref>{{Cite book |last=Maarse |first=H. |url=https://books.google.com/books?id=_OvXjhLUz-oC |title=Volatile Compounds in Foods and Beverages |publisher=CRC Press |year=1991 |isbn=978-0-8247-8390-7 |page=553}}</ref> This acetal is a principal flavour compound in [[sherry]], and contributes fruitiness to the aroma.<ref>{{Cite web |title=June 2007 |url=http://www.beerbrewer.co.uk/2007/06/ |url-status=dead |archive-url=https://web.archive.org/web/20071219120702/https://www.beerbrewer.co.uk/2007/06/ |archive-date=19 December 2007 |access-date=8 December 2007 |publisher=The Beer Brewer}}</ref>

The diketone [[diacetyl]] (2,3-butanedione) has a buttery aroma and is present in almost all distilled beverages. Whiskies and cognacs typically contain more of this than [[vodka]]s, but significantly less than rums or [[brandy|brandies]].<ref>{{Cite book |last=Maarse |first=H. |url=https://books.google.com/books?id=_OvXjhLUz-oC |title=Volatile Compounds in Foods and Beverages |publisher=CRC Press |year=1991 |isbn=978-0-8247-8390-7 |page=554}}</ref>

Polysulfides and thiophenes enter whiskey through the distillation process and contribute to its roasted flavour.<ref name="Cole 361–385" />