Oak Barrels
Whiskey is usually stored in oak barrels (brand new oak barrels for American Bourbon and usually ex-sherry or ex-bourbon barrels in Scotch whisky).
There are three types of oak species used as barrels, Quercus Alba (called “White Oak”, found in America and used in bourbon), Quercus Petraea (called “Sessile Oak”, found in France and used in wine) and Quercus Robur (called “Pedunculate Oak”, found in Spain). The different kind of oak species will add different flavours to an aging spirit in an oak barrel.
The oak barrels will over time change tannin to acetal and acetic acid to fruity esthers. The important factors of oak barrels that impact the taste of the spirit during maturation is hemicellulose, lignin, oak tannin and lactones.
The hemicellulose consists of wood sugars and will add caramelized flavour and colour to the spirit when heated. The longer the maturation, the longer the spirit will be exposed to these factors.
Lignin is basically a binding agent that holds the cellulose together, but when heated it will add flavours such as vanillin to the spirit, in addition to other sweet/spice aromas.
Oak tannin enables the oxidation and creates fragrance to the spirit. Over time, tanning combined with oxygen will form acetals in the spirit
The lactones will add a woody and sometimes coconut-like character to the spirit. Lactones increase during toasting and charring of the oak. It is the lactones that add the distinctive character you will find in American bourbon, and in lesser degree in Scotch whisky.
Black Dog
Black Dogs are stored generally in the white oaks. And aged gracefully in these fine containers. Stop using papers, people! There are better uses to trees! 😉
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