The opportunities to sample a grain whisky are growing, but the number available, bottled either under a brand name or the name of the distillery which produced it, remains relatively small. Meanwhile, the vast majority of grain whisky is blended with malt whisky to produce blended Scotch.
There are seven grain whisky distilleries (compared to 110 malt whisky distilleries) in Scotland. These are: Loch Lomond, Cameronbridge (owned by Diageo), Girvan (William Grant & Sons), Invergordon (Whyte & Mackay), Strathclyde (Chivas Brothers), North British (a joint venture between the Edrington Group and Diageo), with Starlaw (owned by La Martiniquaise) the most recent, operational since 2010.
"Grain whisky from each distillery has its own individual character. The range goes from robust to delicate and sweet, and there's plenty in between. I can't stress enough how large that range is, and when you're making a blended Scotch you can't just substitute one grain whisky for another," says Sandy Hyslop, Ballantine's Master Blender.
How the flavour profile of a grain whisky develops depends on various factors, including the type of grain distilled, the profile of the resulting spirit, the type of cask used, and length of the ageing period.
Grain whisky was traditionally distilled from maize, though most distilleries changed to wheat in the 1980s. Whether, and to what extent, the choice of grain influences the new make spirit depends on the distillation regime, which can either reduce or promote the characteristics of the grain (with maize for example offering greater sweetness than wheat).
Similarly, the higher the distillation strength of the spirit (which must be collected below 94.8% ABV) the lighter the character of the resulting spirit. Furthermore, the lighter the new make spirit, the greater the influence of the cask on the character of the mature grain whisky.
Bourbon barrels, which are the usual choice for ageing, contribute a range of flavours including vanilla and crème caramel.
"Even within two to three months you start to see some sweet vanilla flavour coming through from a Bourbon barrel, together with a hint of colour. The increase in flavour development is pretty linear up to 12-15 years of ageing. After this, the rate of development gets much slower, and I think it continues to slow down past 25-30 years, when grain whisky is smooth and sweet, with lovely vanilla and really nice oak, oranges and honeydew melon notes," says Sandy Hyslop.
Sherry casks are also used, typically contributing a richer sweetness than Bourbon barrels, together with a range of dried fruits, such as raisins.
Kirsteen Campbell, Master Blender for The Famous Grouse explains, "Within two years we see significant colour and character development, with a sherry cask having a greater impact than a Bourbon barrel, as sherry casks provide a higher level of flavour compounds to be extracted by the maturing grain whisky. This is because sherry has a lower alcoholic strength than Bourbon, and when the cask is initially used to age sherry in Spain the sherry extracts less from the cask compared to Bourbon, which has a higher alcoholic strength, and so Bourbon extracts more from the cask during the ageing process in Kentucky."
Although the cask can have a significant impact on the character of a grain whisky, the original distillery character remains evident, even with longer ageing.
"We've bottled 25 and 30 years old grain whiskies which are beautiful whiskies, soft and rounded with really intense toffee and sweet caramel notes from the cask." says Brian Kinsman, Master Blender, William Grant & Sons.
"But you still have the fruitiness of the Girvan distillery character, and if you try grain whisky of the same age from another distillery it will be different, so the distillery character is still there in mature grain whisky," Grain whisky from a single distillery can provide a great range of flavours, but compiling a blend offers other opportunities.
"Hedonism is a blend of grain whiskies from different distilleries, with some whiskies distilled from maize and some from wheat, with some whiskies providing fruitiness and others providing wood character. We launched Hedonism 15 years ago, and this type of blending has always been about creating a particular style," says John Glaser, founder and whisky maker at Compass Box.
The Role of Grain Whiskies in Blended Scotch
Brian Kinsman explains, "Grain whisky contributes way more to a blend than it gets credit for, and is a huge part of the flavour. Grain whisky would be the starting point for me when creating a new blend, as grain whisky defines the style of the blend, then you can move it in different directions using malts. Additional flavours are created through the interaction between grain and malt whiskies, as combining grain whisky with malt whisky creates flavours that neither possess individually.Interaction is a core building block of making a blend, and understanding how the flavours of grains and malts interact is a fundamental aspect of blending, as the final product has to be greater than the sum of the individual parts."
Kirsteen Campbell adds, "It's not just about the flavours that grain whiskies contribute, as a lot of the smoothness and mouthfeel of a blend comes from the grain whiskies."