Every whisky in the world starts as a field of grain. The grain is cooked, its starch is turned to sugar, the sugar is fermented to alcohol and the alcohol is distilled; everything after that is cask and time. So the choice of grain is the first and most fundamental decision in making whisky, and although the barrel often shouts louder in the finished glass, the grain is always underneath, shaping texture, sweetness and the base notes everything else sits on. This guide explains what each of the four main grains brings and why nearly every whisky uses at least a little barley.
The how whisky is made guide places the grain in the process; malting and mashing covers what happens to it next.
Why grain, and why these four
Whisky needs starch, because starch can be converted to fermentable sugar, and it needs enzymes to do the converting. Any cereal supplies the first; only some supply the second in useful quantity. Barley, corn (maize), rye and wheat became the whisky grains because they were the staple cereals of the places where whisky was invented — barley in Scotland and Ireland, corn and rye in North America, wheat as a later addition — and because each had a particular virtue for the distiller. Oats, spelt, triticale and rice have all been used and still are, experimentally, but the four dominate. Oats in particular were common in Irish mashes until the twentieth century and are being revived by a few distillers for the creamy texture they give.
Barley
Barley is the whisky grain because it malts well. Steeped in water and allowed to sprout, a barley grain produces enzymes — chiefly alpha- and beta-amylase — that break its own starch into sugars. Dried at the right moment, the malt retains those enzymes, and they will convert not only barley starch but any other starch in the mash. This is barley’s unique gift. Corn, rye and wheat can be malted, but barley does it more efficiently, which is why almost every mash bill in the world, including those of corn-heavy bourbons and rye whiskeys, includes some malted barley to supply the enzymes.
In flavour, malted barley gives cereal and biscuit notes, a honeyed sweetness, a nutty quality when kilned harder, and a clean, bready foundation. It also carries the smoke, when the malt is dried over peat. Single malt Scotch and Irish single malt are 100 per cent malted barley; the entire character of Speyside, Islay or the Highlands is built on it.
Unmalted barley is a separate ingredient. Irish single pot still whiskey mashes malted and unmalted barley together, and the unmalted grain gives a spicy, oily, slightly green note that malted barley alone does not have. Historically it was used because unmalted barley was taxed less; it survived because the flavour was good.
Barley variety matters to distillers and almost not at all to drinkers. The varieties grown for whisky — Golden Promise in the 1960s and 70s, Optic, Concerto, Laureate and Diablo more recently — are chosen for yield of alcohol per tonne, and the flavour differences between them are subtle. A few distilleries make a point of heritage or specific varieties; most do not, and the cask overwhelms the difference. The glossary has the terms.
Corn
Corn is the sugar factory. It is about 70 per cent starch, more than any other whisky grain, and cheap, and it was the crop that grew best on the American frontier, which is why it became the base of bourbon. Corn has little enzyme of its own, so it is always mashed with malted barley or, in some distilleries, commercial enzymes.
In flavour, corn gives sweetness — round, full, almost buttery — and a soft, oily body. Distilled to high strength it becomes nearly neutral, which is why it is the base of most grain whisky and most Canadian whisky: a clean canvas for cask and blending. Distilled lower and aged in new oak, as bourbon law requires, the corn’s sweetness combines with the barrel’s vanilla and caramel into the profile that defines the category. Corn whiskey — at least 80 per cent corn, usually unaged or lightly aged — tastes of popcorn and sweetcorn and is an acquired taste.
Rye
Rye is the spice. It contributes pepper, baking spice, mint, dill, a grassy dryness and, in high proportions, a bready, slightly sour tang. It is a difficult grain to work with: its high content of pentosans and beta-glucans makes a gummy, sticky mash that foams in the fermenter and sticks to the still, which is one reason rye whiskey nearly disappeared when easier grains were available. Distillers who make it put up with the trouble for the flavour.
Rye is almost always a flavouring grain rather than the whole mash. In bourbon, 10 to 20 per cent rye is standard and above 20 is “high rye”, with the spice rising accordingly. In American rye whiskey it is at least 51 per cent and may be 95 or 100, at which point the spice is everything. Canadian whisky traditionally used a little rye to flavour a corn base, which is why “rye” became the Canadian word for whisky generally. Malted rye, used by a few distillers, is sweeter and less aggressive than raw rye.
Wheat
Wheat is the softener. Low in protein and gentle in flavour, it gives bread, a mild sweetness and a round, smooth texture, and it lets the other ingredients — corn and barrel in a wheated bourbon — do most of the talking. Where rye adds, wheat recedes.
Wheat is the base of most Scottish and Irish grain whisky, chosen for yield and neutrality, and the flavouring grain in the wheated bourbons — Maker’s Mark, Weller, Pappy Van Winkle, Larceny — that have become the most sought-after in Kentucky. A whiskey that is at least 51 per cent wheat is a wheat whiskey in American law and tastes, broadly, of soft bread and vanilla.
How they combine
The proportions of grains in a mash are the mash bill, and the way to read one is to ask what each grain is doing. Our companion piece on reading American mash bills covers the brand-by-brand detail; the principle is simple. Corn is the sugar and the body. Rye or wheat is the personality — spicy or soft. Malted barley is the enzyme, usually around 10 per cent, contributing a cereal note but mostly there to make the mash work. In Scotland and Ireland the question does not arise for malt whisky, which is barley alone, but it arises in every grain whisky and every blend.
How much the grain survives
More than you might think and less than the grain growers would like. Distillation strips a great deal of flavour — the higher the strength off the still, the more is lost, as the pot still vs column still guide explains — and the cask adds a great deal more. But the grain sets the texture, the baseline sweetness and the family of flavours the cask will work with. Rye spice survives twenty years in oak. Corn’s roundness survives any barrel. Barley’s cereal note is the thing you taste in a young Speyside before the cask has had its say. The fermentation guide covers the stage where grain character is most at risk, and the label guide covers where the grain is — and is not — declared.
The grain, in short, is the thing you cannot taste directly and cannot taste without. Learn to find it beneath the cask and whisky becomes much easier to read.
