All about making whisky
While bourbon remains the classic American whiskey with Kentucky as its high seat, many distilleries have recently been challenging this virtual monopoly by offering an alternative to the ‘king of bourbon’.
The last 15 years have seen a surge in the number of micro-distilleries opening across the country: the Clear Creek distillery in Oregon (McCarthy's), the Anchor Distillery near San Francisco (Old Potrero) and more recently the Tuthilltown distillery in New York (Hudson).
Most American whiskeys are made from a three-grain blend (mashbill) consisting of corn, rye and malted barley. The main grain accounts for at least 51% of the mix, such as corn for bourbon and rye for rye whiskey. Once the corn content exceeds 80%, the whiskey is called a corn whiskey. The other grains are known as small grains. The proportion of small grains used partially determines the character of the whiskey.
The higher the proportion, the richer and more flavoursome the whiskey. The Maker's Mark distillery uses winter wheat instead of rye, which provides floral notes.
Kentucky has substantial water reserves. This very pure water is low in iron thanks to a natural filtering process provided by the limestone sediment that is present across the state. These conditions enhance the soft, mellow nature of its whiskeys. Water is also involved in the brewing stage. During this process, the corn is ground into a rough flour and cooked at high pressure in a stainless steel vat filled half-way with water to release the starch. When the temperature of the must falls back to 70°C, the small grains are incorporated into the brewing vat.
Finally, the nature of the water facilitates the action of the yeast during fermentation, allowing the whiskey to take on fruity (citrus) and floral notes.
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Water is involved in the brewing stage.
‘White dog’, the equivalent of new-make spirit, is the result of a double distillation process: the first distillation is carried out continuously in a patent or column still, while the second takes pace in a pot still known as a thumper or doubler. The middle cut is removed when the alcoholic content reaches between 60% and 80% (it cannot be distilled beyond 80%). The lower the strength, the more the whiskey will be characterised by aromas evocative of the grains and fermentation.
When the alcohol content approaches the 80% mark, the whiskey releases more tannins, sugar and vanillin from the barrel.
Produced on the bourbon model, Tennessee whiskey differs from the former in the charcoal mellowing process. This involves filtering through a 3-metre layer of wood charcoal prior to barreling, and takes about ten days.
The charcoal infuses the whisky with subtle smoky notes and aromas of burnt wood, while eliminating some oily particles. Tennessee whiskeys, notably Jack Daniel's, are thus drier than other whiskeys.
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The ageing stage is crucial in determining the character of the whiskey. Distilleries are required to use small (180 litre) new white oak (Quercus alba) barrels. These barrels undergo a charring process that involves burning the inside to enable an enhanced exchange with the wood. The starch contained in the wood is converted into a thin caramelised layer that coats the inside of the barrel.
There are four degrees of charring. The higher the rate of burning, the more the barrel will influence the whiskey. All of these characteristics combined with summer heatwave temperatures encourage fast maturing and the development of creamy notes of vanilla, caramel, toffee and a natural amber colour (the addition of caramel is prohibited under American law), the hallmark of American whiskey.