Scotch whisky is made from three ingredients: malted barley, water and yeast. There are two basic whisky types distilled in Scotland: malt whisky and grain whiskey and each involves a different production process. Malt whisky goes through five basic stages in the production.
The first four stages are complete in a matter of days while the Maturation can take anything from the legal minimum of three years to over 20 years.
Grain whisky is produced by a Coffey or Patent still and uses wheat, maize or other cereals rather than barley.
In making Scotch whisky, the process begins with the malting of the barley, which is first soaked in large tanks of water for up to 4 days before being spread out on the floor of the malting house to germinate. Over the next 12 days or so, the barley is turned over, either by hand in a traditional manner or more likely nowadays by machine, to allow it to sprout, causing the starch in the grain to be converted to sugar.
The peat smoke is allowed to filter through the drying barley to different degrees by each distillery and can often be tasted in the final whisky itself. The kilns traditionally had pagoda-shaped chimnies and these have become the characteristic mark of every distillery.
The malted barley is now roughly ground and the resulting grist is mixed and agitated with several flushes of hot water in a large cylindrical vat called the mash tun, there the sugars in barley grist dissolve to produce a hot, sweet, non-alcoholic liquid, the wort.
After mashing, the wort is cooled to allow the addition of the yeast which takes place in large wooden or metal vats called washbacks. Fermentation now begins and the sugary wort is converted into a low-strength alcohol called wash. At the outset, the wash is very similar in strength to beer (around 7% ABV) but by the end of the 50-hour fermentation, this has increased to around 25%.
Scotch whisky is usually distilled twice in a distinctive swan-necked copper pot stills. The alcohol in the wash evaporates first and rises as steam through the narrow neck of the still to the warm, a condensing coil to produce a distillate called low wine.
The low wines are then passed through the spirit still to repeat the process.This raises the alcohol content of the resulting liquor to between 70% to 80% ABV.
The precise shape of the still is a crucial part of the distillation process and can have a decisive impact upon the character of the whisky it produces. For instance, stills with short necks produce whiskies with heavier oils which give more intense flavors, whereas long or high necked stills produce less-intense whiskies because of the lighter oils produced during distillation.
From the second distillation, the crystal-clear spirit is run off via the glass-fronted spirit safe. This 'safe' is heavily padlocked by the Customs & Excise to prevent any possibility of the distillery siphoning off the spirit to avoid paying the legal duty on it.
The final stage in the process is allowing the new whisky to mature in wooden barrels (or casks) for several years to allow it to develop the desired coloring and flavor characteristics.
The choice and quality of these barrels play a crucial role in the character of the final product. New casks are never used since these have nothing to impart to the new spirit. Instead, casks which have previously been filled with fino, amontillado or oloroso sherry or bourbon are preferred.
Once it is determined that the whisky is ready, whiskies from various distillations are mixed so that the subtle differences between each will be removed, coloring is added and it is chill-filtered to remove the oils which cause cloudiness when ice is added. Finally the mix is diluted to around 40% or 43% ABV for bottling. Some independent bottlers purchase casks of finished whiskies and do simply decant them straight into bottles - no dilution, no chemical alterations, no standardisation.
(Source: The Official Visit Scotland, National Tourism Board)
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