Single Malt
Whiskey, made one batch at a time
Single malt whiskey is a whiskey that is distilled in a single distillery,
and made completely from a single type of malted grain, traditionally
barley, (although there are also single malt rye whiskeys, but not Irish
Whiskeys). Most single malt whiskeys are distilled using a pot still.
Single malts are produced all over the world, but the best known single
malt whiskeys come from Ireland, Scotland and Japan.
All single malt whiskey goes through a similar batch production process. At bottling time various batches are mixed together to achieve consistent flavors from one bottling run to the next. However, some variation can occur.
Water is first added to the barley to make the barley sprout, it is mixed with ground barley grist to create what is called mash and it is used to dilute most whiskey before maturation and once again before bottling.
Most new malt whiskey is diluted to between 63%-63% before it is placed in casks to age. Today, many distilleries use distilled water for diluting whisky before it is casked as well as for diluting the whisky to bottling strength from 40-46% Alcohol by Volume after maturation. Much un-aged whisky is shipped in tanker trucks to central warehouses where local tap water is used to dilute it before casking, and again at bottling time.
Since huge amounts of water are used during the process of whisky production, water supplies are a key factor for the location of any distillery, making the relatively small rainy island of Ireland ideal for all Whiskeys.
Barley, yeast and water are the only ingredients required in the production of single malt whiskey. the barley used to make the whiskey is malted by soaking the grain in water for 2-3 days and then allowing it to sprout to convert starch into fermentable sugars.
The germination is halted by heating the barley after 3-5 days, when the optimum amount of starch has been converted to fermentable sugars. The method for drying the germinated barley is by heating it with hot air produced by an oil, coal, peat or even electric heat source.
In some cases in Irish whiskey, some level of peat smoke is introduced to the kiln to add phenols, a smoky aroma and flavor that is traditionally found in Scotch whisky. Some of the more intensely smoky malts have phenol levels between 25 and 50 parts per million. The three Scottish single malt whiskeys with a reputation for being the most peaty are Ardbeg, Laphroaig and Lagavulin, all from Islay. More subtle malts can have phenol levels of around 2–3 ppm.
The malt is milled grist, and added to hot water to extract the sugars. The extraction is done in a large kettle called a mash tun. At first, the hot water dissolves the sugars and enzymes in the grist. Then the enzymes act on the starch left over from the malting stage, continuing the conversion to sugar, and producing a sugary liquid called wort. Typically, each batch of grist is mashed three times or so to extract all fermentable sugars.
Yeast is then added to the wort in a washback. Washbacks are commonly made of Oregon Pine or stainless steel. The yeast feeds on the sugars and as a by-product produces both carbon dioxide and alcohol and this process is called Fermentation and can take up to three days to complete. When complete, the liquid has an alcohol content of 5 to 7% by volume, and is now known as wash. Up until this point the process is similar to the production of beer.
The wash is then pumped into a copper pot still, known as the wash still, to be distilled. The wash is heated, boiling off the alcohol, which has a lower boiling point than water; the vapor is collected in a condenser which has been submerged in cool water. The lower temperatures cause the vapor to condense back into a liquid form.
This spirit, known as low wine has an alcohol content of about 20 to 40%. The low wines are then pumped into a second pot still, known as the spirit still, and distilled a second, (and sometimes a third) time. The final spirit called "new make spirit" generally has an alcohol content of 60 to 70%.
Much of the body, or mouth feel, of the final whiskey is believed to come from the size and shape of the stills used in its production. When a still wears out and has to be replaced, or when a distillery decides to expand the number of stills it operates, precise measurements of the existing stills are taken to ensure the new stills are reproduced exactly like the old.
The un-aged whiskey, is then placed in oak casks to mature. The whisky continues to develop and change as it spends time in the wood, and maturation periods of twenty years or more are not uncommon for fine whiskeys. Each year spent in the wood reduces the alcohol content of the whiskey, as the alcohol evaporates through the porous oak; the lost alcohol is known as the angel's share.
The selection of casks has a profound effect on the character of the final whiskey. A common source of casks is American whiskey producers, as U.S. laws require that bourbon be aged in new oak casks. Bourbon casks impart a characteristic vanilla flavor to the whiskey. Sherry casks are also commonly used. This practice arose because sherry used to be shipped to Britain from Spain in the cask rather than having been bottled, and the casks were expensive to return empty and were unwanted by the sherry cellars. In addition to imparting the flavors of their former contents, sherry casks lend maturing spirit a heavier body and a deep amber and sometimes reddish color. Stainless steel shipping containers, however, have reduced the supply of wooden sherry casks, to the extent that the Macallan Distillery builds casks and leases them to the sherry cellars in Spain for a time, then has them shipped back to Scotland. Other casks used include those that formerly held port wine and madeira, while experiments with used rum and cognac casks are being performed.
To be called a single malt whiskey, a bottle may only contain whiskey distilled from malted barley produced at a single distillery. If the bottle is the product of single malt whiskeys produced at more than one distillery, the whiskey is called a vatted malt, blended malt, or pure malt. If the single malt is mixed with grain whiskey, the result is a blended whiskey. Single malts can be bottled by the distillery that produced them or by an Independent Bottler.
The age statement on a bottle of single malt whiskey is the age of the youngest malt in the mix, as commonly the whiskeys of several years are mixed together in a vat to create a more consistent house style.
On occasion the product of a single cask of whiskey is bottled and released as a "Single Cask."
While "cask-strength", or undiluted, whiskey (often having an alcohol content as high as 60%) has recently become popular, the vast majority of whiskey is diluted to its "bottling strength" - between 40% and 46% ABV - and bottled for sale.
It should also be noted that for whiskey, unlike wine, the maturation process does not continue in the bottle.
The first written record of whiskey comes from 1405 in Ireland, the production of whiskey from malted barley is first mentioned in Scotland in an entry on the 1494 Exchequer Rolls, which reads "Eight bolls of malt to Friar John Cor, by order of the King, wherewith to make aqua vitae." Single malt whiskey is associated with the Scottish tradition, although there are many fine Irish single malt whiskeys as well.
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