Barrel for at least two years in new, charred oak containers. Other forms of whisky aged in used barrels cannot be called "straight". International laws require any whisky bearing the label "Scotch" to be distilled and matured in Scotland for a minimum of three years and one day in oak casks. By Canadian law, Canadian whiskies must "be aged in small wood for not less than three years", and "small wood" is defined as a wood barrel not exceeding capacity. Since the U.S. law requires the use of new barrels for several popular types of whisky, which is not typically considered
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