Scotch Whisky
Scotch whisky is prized all over the world for its fine taste. There are four categories of this whisky:
- Single Malt - made from the malted barley output of a single distillery. This is distilled in copper pot stills. Whisky from different casks within that distillery may be blended to create this, although single cask releases are also sometimes made.
- Blended Malt (also knows as vatted malt) - this is a blend of several different malt whiskies from different distilleries.
- Blended Whisky - this is a blend of malt and grain whiskies. Typically, the ratio is 60% grain and 40% malt whisky.
- Grain Whisky- this contains whisky made from wheat or corn using a continuous still (rather than a pot still as in malt whisky production)
In order to be deemed worthy of the name “Scotch” the whisky must meet the standards set down by the Scotch Whisky Order of 1990. This requires the following:
- The whisky must be distilled in Scotland using water and malted barley, to which only the whole grains of other cereals may be added. These must have been:
- Processed at that distillery into a mash
- Converted to fermentable substrate by means of endogenous enzyme systems (not artificial)
- Fermented by adding yeast
- Processed at that distillery into a mash
- The alcoholic strength by volume at distillation must not exceed 94.8%
- The whisky must be matured in an excise warehouse in oak casks not exceeding 70 litres for a minimum of three years
- No substances other than water or spirit caramel (to maintain consistent colouring) may be added.
The age statement on a bottle of Scotch Whisky indicates the youngest whisky component, but may contain far older whiskies.
Malt whisky can only contain barley grains and the production starts after the barley has malted, which means it has almost germinated in water. The malted barley is then dried. Some distilleries add peat to the fire to give an earthy taste to the drink. The peat smoke binds to the wet grains. The distillery then grinds the malt very finely into coarse flour called grist, after which it is mixed with hot water and allowed to steep. After the mixture has cooled, yeast is added and the mixture, called wash, is allowed to ferment. At this stage it contains about 7% alcohol.
Once the fermentation stage is complete, the distillation begins. This increases the alcohol content, while removing any impurities, such as methanol. Pot stills are used for malt whisky and Coffey stills are used for grain whisky. In distilling malt whisky, the wash is poured into a large still and brought to a boil. The alcohol rises to the top through evaporation and goes through a condenser, which converts it back to a liquid. This liquid alcohol, called low wine, is then sent through the distillation process a second time. All Scotch malt whiskies must be distilled twice. It is then culled for alcoholic content. The highest and lowest contents are saved for future distillation, but the middle content goes into the oak casks for maturation.
For grain whisky, the column still only performs one distillation. This is the cheaper form of Scotch whisky on the market.
As the whisky matures in the casks, it does lose some of its volume and alcohol content through evaporation - this is known as the angels share. Once it has been properly aged, it is then bottled and in some cases diluted to reduce the high alcohol content. Some whiskies go through a chill filtration process before bottling, in which the whisky is chilled to 0ºC before being passed through a filter. This helps to remove some of the impurities that may be in the whisky from the cask and keeps it from becoming hazy when poured as a drink with ice in the glass.
More and more distilleries, especially the smaller independents, are offering expressions that do not undergo this chill filtration process, so as to retain more of the flavour - often these are released at cask strength.