Whisky or whiskey is a type of distilled alcoholic beverage made from fermented grain mash. Different grains are used for different varieties, including barley, malted barley, rye, malted rye, wheat, and corn. Whisky is typically aged in wooden casks, made generally of charred white oak. The spelling whisky (plural: whiskies) is generally used in Canada, Japan, Scotland, England, and Wales—while whiskey (plural: whiskys) is more common in Ireland and the United States. Whisky is a strictly regulated spirit worldwide with many classes and types. The typical unifying characteristics of the different classes and types are the fermentation of grains, distillation, and aging in wooden barrels.
Whiskies do not mature in the bottle, only in the cask, so the “age” of a whisky is only the time between distillation and bottling. This reflects how much the cask has interacted with the whisky, changing its chemical makeup and taste. Whiskies that have been bottled for many years may have a rarity value, but are not “older” and not necessarily “better” than a more recent whisky that matured in wood for a similar time. After a decade or two, additional aging in a barrel does not necessarily improve a whisky.
Most whiskies are sold at or near an alcoholic strength of 40% abv, which is the statutory minimum in some countries – although the strength can vary, and cask-strength whisky may have as much as twice that alcohol percentage.
Whisky or whisky-like products are produced in most grain-growing areas. They differ in base product, alcoholic content, and quality.
- Malt whisky is made primarily from malted barley.
- Grain whisky is made from any type of grains.
Malts and grains are combined in various ways:
- Single malt whisky is whisky from a single distillery made from a mash that uses only one particular malted grain. Unless the whisky is described as single-cask, it contains whisky from many casks, and different years, so the blender can achieve a taste recognisable as typical of the distillery. In most cases, single malts bear the name of the distillery, with an age statement and perhaps some indication of some special treatments such as maturation in a port wine cask.
- Blended malt whisky is a mixture of single malt whiskies from different distilleries. If a whisky is labelled “pure malt” or just “malt” it is almost certain a blended malt whisky. This was formerly called a “vatted malt” whisky.
- Blended whiskies are typically made from a mixture of malt and grain whiskies — often along with neutral spirits, caramel, and flavouring. A whisky simply described as a Scotch, Irish, or Canadian whisky is most likely a blend. A blend typically contains whisky from many distilleries so that the blender can produce a flavour consistent with the brand. The brand name (e.g., Chivas Regal, Cutty Sark) usually does not, therefore, contain the name of a distillery. Jameson Irish Whiskey is an exception, as it comes from only one distillery.
Scotch whiskies are generally distilled twice, although some are distilled a third time and others even up to twenty times.[ Scotch Whisky Regulations require anything bearing the label “Scotch” to be distilled in Scotland and matured for a minimum of three years in oak casks, among other, more specific criteria. An age statement on the bottle, in the form of a number, must reflect the age of the youngest Scotch whisky used to produce that product. A whisky with an age statement is known as guaranteed age whisky. Scotch whisky without an age statement may, by law, be as young as three years old. The basic types of Scotch are malt and grain, which are combined to create blends. The distinctive smoky flavour that can often be found in Scotch, is due to the use of peat smoke to treat their malt. Scotch malt whiskies are divided into five main regions: Highland, Lowland, Islay, Speyside and Campbeltown.
Irish whiskys are normally distilled three times, Cooley Distillery being the exception as they also double distill. Though traditionally distilled using pot stills, the column still is now used to produce grain whisky for blends. By law, Irish whisky must be produced in Ireland and aged in wooden casks for a period of no less than three years, although in practice it is usually three or four times that period. Unpeated malt is almost always used, the main exception being Connemara Peated Malt whiskey.
There are several types of whisky common to Ireland: single malt, single grain, blended whiskey and pure pot still whiskey.
American whiskey is distilled from a fermented mash of cereal grain. It must have the taste, aroma, and other characteristics commonly attributed to whiskey.
Some types of whiskey listed in the United States federal regulations are:
- Bourbon whiskey—made from mash that consists of at least 51% corn (maize)
- Corn whisky—made from mash that consists of at least 80% corn
- Malt whisky—made from mash that consists of at least 51% malted barley
- Rye whisky—made from mash that consists of at least 51% rye
- Rye malt whisky—made from mash that consists of at least 51% malted rye
- Wheat whisky—made from mash that consists of at least 51% wheat
These types of American whisky must be distilled to no more than 80% alcohol by volume, and barrelled at no more than 125 proof. Only water may be added to the final product; the addition of colouring or flavouring is prohibited. These whiskeys must be aged in new charred-oak containers, except for corn whiskey which does not have to be aged. If it is aged, it must be in uncharred oak barrels or in used barrels. Corn whiskey is usually unaged and sold as a legal version of moonshine.
If one of these whiskey types reaches two years aging or beyond, it is additionally designated as straight, e.g., straight rye whiskey. A whisky that fulfils all above requirements but derives from less than 51% of any one specific grain can be called simply a straight whisky without naming a grain.
US regulations recognize other whisky categories, including:
- Blended whisky—a mixture that contains straight whisky or a blend of straight whiskeys and, separately or in combination, whiskey or neutral spirits, and may also contain flavourings and colourings
- Light whiskey—produced in the US at more than 80% alcohol by volume and stored in used or uncharred new oak containers
- Spirit whiskey—a mixture of neutral spirits and at least 5% of certain stricter categories of whiskey
American blended whiskeys combine straight whiskey with neutral grain spirit (NGS), flavourings and colourings. The percentage of NGS must be disclosed on the label and may be as much at 80% on a proof gallon basis. Blended whiskey has the same alcohol content as straight whisky but typically has a milder flavour.
Another important labelling in the marketplace is Tennessee whisky, of which Jack Daniel’s, George Dickel, Collier and McKeel, Jailers, and Benjamin Prichard’s are the only brands currently bottled. In practice, it is essentially identical to bourbon whisky. Whiskey sold as “Tennessee whisky” is defined as Bourbon under NAFTA and at least one other international trade agreement, and is similarly required to meet the legal definition of Bourbon under Canadian law.
By Canadian law Canadian whiskies must be produced and aged in Canada, be distilled from a fermented mash of cereal grain, be aged in wood barrels with a capacity limit of 700 litres for not less than three years, and “possess the aroma, taste and character generally attributed to Canadian whisky”.The terms “Canadian Whisky”, “Rye Whisky”, and “Canadian Rye Whisky” are legally indistinguishable in Canada and do not require any specific grain in their production. Canadian whiskies may contain caramel and flavouring in addition to the distilled mash spirits, and there is no maximum limit on the alcohol level of the distillation.To be exported under one of the “Canadian Whisky” designations, a whisky cannot contain more than 9.09% imported spirits.
Whiskies and other distilled beverages, such as cognac, and rum are complex beverages that contain a vast range of flavouring compounds, of which some 200 to 300 are easily detected by chemical analysis. The flavouring chemicals include “carbonyl compounds, alcohols, carboxylic acids and their esters, nitrogen- and sulphur-containing compounds, tannins and other polyphenolic compounds, terpenes, and oxygen-containing heterocyclic compounds” and esters of fatty acids. The nitrogen compounds include pyridines, picolines and pyrazines.
Flavours from distillation
The flavouring of whisky is partially determined by the presence of congeners and fusel oils. Fusel oils are higher alcohols than ethanol, are mildly toxic, and have a strong, disagreeable smell and taste. An excess of fusel oils in whisky is considered a defect. A variety of methods are employed in the distillation process to remove unwanted fusel oils. Traditionally, American distillers focused on secondary filtration using charcoal, gravel, sand, or linen to remove undesired distillates.
Canadian distillers traditionally employ column stills, which can be controlled to produce an almost pure (and less flavourful) ethanol known as neutral grain spirit or grain neutral spirit (GNS). Flavour is restored by blending the neutral grain spirits with flavouring whiskies.
Acetals are rapidly formed in distillates and a great many are found in distilled beverages, the most prominent being acetaldehyde diethyl acetal (1,1-diethoxyethane). Among whiskies the highest levels are associated with malt whisky. This acetal is a principal flavour compound in sherry, and contributes fruitiness to the aroma.
The diketone diacetyl (2,3-butanedione) has a buttery aroma and is present in almost all distilled beverages. Whiskies and cognacs typically contain more of this than vodkas, but significantly less than rums or brandies.
Flavours from oak
Whisky that has been aged in oak barrels absorbs substances from the wood. One of these is cis-3-methyl-4-octanolide, known as the “whisky lactone” or “quercus lactone”, a compound with a strong coconut aroma.
Commercially charred oaks are rich in phenolic compounds. One study identified 40 different phenolic compounds. The coumarin scopoletin is present in whisky, with the highest level reported in Bourbon whiskey.
Flavours and colouring from additives
Depending on the local regulations, additional flavourings and colouring compounds may be added to the whisky. Canadian whisky may contain caramel and flavouring in addition to the distilled mash spirits. Scotch whisky may contain added (E150A) caramel colouring, but no other additives. The addition of flavourings is not allowed in American “straight” whisky, but is allowed in American blends.
Whisky is often “chill filtered”: chilled to precipitate out fatty acid esters and then filtered to remove them. Most whiskies are bottled this way, unless specified as unchillfiltered or non chill filtered. This is done primarily for cosmetic reasons. Unchillfiltered whiskys often turn cloudy when stored at cool temperatures or when cool water is added to them, and this is perfectly normal.
Shipment / Storage / Risk factors
High value distillate. Fumes from hogs heads of whisky can corrode galvanized metal surfaces.
For overseas transport consult the IMDG Code (International Maritime Dangerous Goods Code) and applicable MSDS advice (Material Safety Data Sheet).