Single Malt Scotch Whisky 101

Posted by Keith Saunders

Posted: October 6, 2008 - 4:37 pm

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Here is some information I recently presented at my Whiskey vs Whisky Tasting.

Single Malt Scotch Whisky

Single Malt Scotch is a type of single malt whisky, distilled by a single distillery in a potstill, using malted barley as the only grain ingredient in Scotland. As with any Scotc whisky, a Single Malt Scotch must be distilled in Scotland and matured in oak casks in Scotland for at least three years (most single malts are matured for longer).
• "Single" indicates that all the malts in the bottle come from a single distillery. Multi-distillery malts are usually called "blended malt", "vatted malt" or "pure malt".
• "Malt" indicates that the whisky is distilled from a single "malted" grain. Not all grains can be malted - (rye is another grain which can be malted) - but in the case of single malt Scotch, barley is always the grain used.

Production

All single malt Scotch goes through a similar batch production process, as outlined below. At bottling time various batches are mixed together or vatted to achieve consistent flavours from one bottling run to the next.

Water

Water is used in all phases of the production of whisky. It is added to the barley to promote germination, it is mixed with ground barley grist to create a mash and it is used to dilute most whisky before maturation and once again before bottling.

Most distilleries use different water sources in the various steps.
Most new-make malt whisky is diluted to about 63.5% before it is placed in casks to mature. These days, many distilleries are using distilled water for diluting whisky before it is casked as well as for diluting the whisky to bottling strength (40-46% Alcohol by Volume (ABV)) after maturation.

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.

Malting

The barley used to make the whisky is "malted" by soaking the grain in water for 2-3 days and then allowing it to germinate to produce the necessary enzymes required to convert starch into fermentable sugars.
Traditionally each distillery had its own malting floor where the germinating seeds were regularly turned. Most of the distilleries use commercial "maltsters" who prepare each distillery's malt to exact specifications, but the "pagoda roof" (many now false) which ventilated the malting floor can be seen at nearly every distillery.
The germination is halted (by heating) after 3-5 days, before the starch begins to be converted into the fermentable sugars. The method for drying the germinated barley is by heating it with hot air produced by an oil, coal or even electric heat source.
In most cases, some level of peat smoke is introduced to the kiln to add phenols, a smoky aroma and flavour to the whisky. Some of the more intensely smoky malts from Islay have phenol levels between 25 and 50 parts per million (ppm). The three smokiest/peatiest malts, in order of phenol concentration, are Ardbeg, Laphroaig (la-froyg) and Lagavulin (lagga-voolin), all from Islay. More subtle malts can have phenol levels of around 2–3 ppm.

Mashing

The malt is milled into a coarse flour (grist), and added to hot water to activate the enzymes which will convert starches to fermentable sugars. Long starch chains are broken into glucose, maltose, and maltriose, which are able to be fermented by yeast.
The extraction is done in a large kettle (usually made of stainless steel) called a mash tun. At first, the hot water activates the enzymes by providing an optimal temperature for activity in the grist. The enzymes act on the starch to convert it into sugar, and producing a sugary liquid called wort.

Fermentation

Yeast is added to the wort in a large vessel (often tens of thousands of litres) called 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; 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 has been quite similar to the production of beer.
Maturation

By law, Scotch whisky must be matured for a minimum of three years in oak casks.

The "new-make spirit", or unaged whisky, is then placed in oak casks to mature. By law, all Scotch whisky must be aged for a minimum of three years in oak casks in Scotland; though many single malts are matured for much longer. 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. Each year spent in the wood decreases the alcohol content of the whisky.
The selection of casks has a profound effect on the character of the final whisky. Single malt Scotch is too delicate to be aged in new oak casks, as new oak would overpower the whisky with tannin and vanillin, making it overly astringent. Thus used casks are needed. The most common source of casks is American whiskey producers, as U.S. laws require that bourbon and Tennessee whiskey be aged in new oak casks. Bourbon casks impart a characteristic vanilla flavour to the whisky. An important minority of whisky maturation occurs in sherry casks.

Regions and Single malt origins.
Flavour, aroma, and finish differ widely from one single malt to the next. Single Malt Scotch whiskies are categorised into the following whisky-producing regions.
• Speyside Single Malts
• Highland Single Malts
o Island Single Malts A sub-section of the Highland region
• Lowland Single Malts
• Islay Single Malts
• Campbeltown Single Malts

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