Paul John (whisky) evaporation during aging, known as the angels' share, is also higher in India, at 10–12% per year, than in Scotland, where the annual evaporative loss is about 2%. This leaves a hogshead with only 150 bottles left in it, after three years, compared to around 350 in a Scotland. Michael John describes it this way, "Whisky matured at these temperatures simply cannot be aged for the kind of time expected with Scotch, even trying to mature our whisky for just 10 years would leave barely a bottle of liquid in the barrel. Fortunately, the heat actually speeds up the maturation
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