Scotch whisky whisky" is any spirit that qualifies as a single malt Scotch whisky or as a blended Scotch whisky. The latter exclusion is to ensure that a blended Scotch whisky produced from single malt(s) and single grain(s) distilled at the same distillery does not also qualify as single grain Scotch whisky. Three types of blends are defined for Scotch whisky: The five Scotch whisky definitions are structured in such a way that the categories are mutually exclusive. The 2009 regulations changed the formal definition of blended Scotch whisky to achieve this result, but in a way that reflected traditional and current
Whisky compound in sherry, and contributes fruitiness to the aroma. 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 vodkas, but significantly less than rums or brandies. Polysulfides and thiophenes enter whiskey through the distillation process and contribute to its roasted flavor. Whisky that has been aged in oak barrels absorbs substances from the wood. One of these is cis-3-methyl-4-octanolide, known as the "whisky lactone" or "quercus lactone", a compound with a strong coconut aroma. Commercially charred oaks are rich in phenolic compounds. One study