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Whiskey is defined simply as a "distilled spirit made from grain mash". In this article, we will take a deep dive into the main crops from which whiskey is made with a particular emphasis towards grades, growing conditions, and their impact on the resulting whiskeys' flavors.
Whiskey mash bills are primarily comprised of mixtures of four primary grains:
- Barley
- Corn
- Rye
- Wheat
Barley - The Single Malt King
Known for its use in Scotch, Japanese, and Irish whiskey, Barley is the grain of choice for single malts, including the burgeoning American Single Malt category. It is a historic crop due to its easy-to-grow and relatively hearty nature and is still the most widely used grain in the world. Known for contributing a warm, nutty profile to whiskey, you may see high barley content whiskies accompanied by tasting notes like toast, biscuit, toffee, cereal, or cocoa. Barley is most often malted (let germinate and then cooked to stop the growth, allow yeast greater access to the grain's sugars), but the other grains can also be malted as well.
Barley Growing Conditions
Relatively inexpensive and easy to grow, barley provides excellent erosion control and weed suppression. Some farmers use it to fill short crop rotation niches or protect top soil during droughts due to its quick growing cycle and tolerance for dry conditions.
- Climate: Barley is an annual cereal grain that prefers cooler climates but can tolerate a range of conditions. It's particularly suited to regions with a growing season of 90-110 frost-free days.
- Soil: Well-drained loamy soils are ideal, though barley can grow in sandy or clay soils provided they aren't waterlogged. Barley has a relatively high tolerance for salt compared to other small gains and tolerates alkaline soils better than any other cereal (pH between 6.0-7.5).
- Water: It requires about 14 to 20 inches of water during the growing season, but it's drought-resistant compared to other grains.
Popular Barley Varietals in Whiskey
While their are more than five-thousand different strains of barley, only ten are approved for Scotch production. Malt whisky distillers prefer barley strains with a low nitrogen content that are high in starch and have a large grain size, enzyme potential, and ability to germinate. High nitrogen barley is instead more often used in grain whisky. In general, two-row barely (where the head of the plan only has two rows of kernels) is preferred to six-row barley because the grains are more consistently sized. Pretty much all of the below varieties were derived from the same parent species, Hordeum distichon, so they are similar in flavor and therefore interchangeable.
- Established Varieties - Optic, Belgravia, Concerto, Propino, Quench, and Shuffle
- Newer Varieties - Moonshine, Odyssey, Chronicle, and Overture
- Deprecated - Oxbridge, Maris Otter, Prisma, Chariot, Triumph, and Golden Promise are seldom planted as they have been surpassed by the higher yield varieties above.
In the UK, barley is graded on a scale of 1-9 and only the top three grades are suitable for whisky production.
Corn - Sire of Bourbon
From the Aztec's Maize to Kentucky Bourbon, new world corn is abundant. Corn is known for its high starch content which yeast convert into plentiful sugars, mostly metabolized by the yeast to produce alcohol. Corn is somewhat neutral and does not have a major impact on the final flavors of the spirit. Providing a cheap source of sugars to convert to alcohol is its major function which is why it is often paired with other more flavorful grains in mash bills. Most flavors attributed to corn are actually from the barrel, though colored or heirloom varieties may add more unique tastes.
Corn Growing Conditions
- Climate: Corn thrives in warm climates with long, frost-free periods (120-180 days). It's sensitive to frost, requiring soil temperatures above 10°C (50°F) for germination.
- Soil: Needs deep, fertile, well-drained soil with a pH of 6.0 to 6.8.
- Water: Corn is relatively water-intensive, needing 20-30 inches of water per growing season, with critical periods during tasseling and ear development.
What Types of Corn are use in Bourbon?
- Dent Corn: These hybrid corn species have kernels with a distinctive indentation at the corn of the kernel that forms as it is dried. This is the primary type used in bourbon, known for its high yield and starch content. Varieties like 'Yellow Dent' are common. No.1 or No.2 quality grade per the USDA quality guidelines (based on % of heat damage, broken corn, or foreign material). It is not known for being particularly flavorful. You may see a name like "Yellow Dent No.2" as describing this variety.
- Heirloom Varieties - Purple Corn, Bluddy Butcher, Floriani Flint, and others may be selected. Often by craft producers looking for niche or interesting flavors.
Rye - A Flash of Heat & Pepper
Known for imparting a spicy, bold flavor to whiskey, Rye has been cultivated by humans for thousands of years. Originally a weed in wheat and barley fields of the Far East, it was eventually cultivated in Europe where conditions did not permit the growing of other grains. In addition to whiskey, some vodkas such as Belvedere are made using rye, traditional in Eastern Europe where potatoes were prioritized for eating. Note that this is a discussion of cereal rye, not annual ryegrass.
Growing Conditions
Rye is known for being the hardiest of all cereal crops and can be seeded later in the growing season that other grains. It is by far the most common cover crop in America, being grown primarily for the benefit of the soil rather than harvest (erosion, nitrogen, and biomass). Rye also experiences few diseases and mulched rye can even help protect other crops.
- Climate: Hardy in cooler climates, rye can be grown in areas where other grains fail, requiring 60-100 frost-free days.
- Soil: Adaptable to poor, sandy, or acidic soils with a pH range from 5.0 to 7.0, though it prefers well-drained loam. It is more sensitive to seeding depth than other grains and shouldn't be planted more than 2in below ground.
- Water: Less water-intensive than corn, needing about 12-18 inches during its growing period.
Popular Varieties for Whiskey
- Common Rye: Thew most widely used varietal, common rye is known for a hardy nature and hints of pepper, clove, and baking spice.
- Winter Rye: Planted in fall, it's known for its spicy, bold flavors in whiskey. Hybrid varieties like 'Danko' and 'Brasetto' are popular, helping to add a little bit more sweetness than common rye. Rosen Rye and Wrens Abruzzi rye have historical roots in Pennsylvania and New York and may be featured in historic brands from those regions.
- Spring Rye: Planted in spring for a shorter growing season, often resulting in a slightly different flavor profile. Most rye planted in the spring is common rye.
Wheat - Oh How I Love it
Most often used in wheated Bourbons, wheat adds an additional level of sweetness, smoothness, and creaminess to the final spirit. Wheat is commonly grown as a cash grain but can be grown as ground cover and is less likely to turn to a weed than barley or rye. It is slower to mature but is increasingly grown instead of rye due to being significantly easier to manage in the spring season.
Growing Conditions
- Climate: Wheat prefers temperate climates but has varieties suited to different conditions, from winter to spring wheat, needing 110-130 days between sewing and harvest.
- Soil: Well-drained, fertile loam with a pH of 6.0 to 7.0 is optimal.
- Water: Requires about 18-22 inches of water, with critical periods during tillering and grain filling.
Winter wheats are planted in the autumn and require a period of low temperatures during which they remain dormant until being awakened to grow to maturity by the spring thaw.
Popular Varieties for Whiskey
There are really only two widely used wheat varietals in whiskey, soft and hard red winter wheat. There are winter and spring varieties for both white and red wheat.
- Soft Red Winter Wheat: Known for a softer, sweeter flavor, used in some bourbons and wheat whiskeys. It has lower protein and gluten content, making it more versatile and easier to use. It has a shorter growing seasons and prefers more temperate climates. About 15% of US wheat production is soft red winter wheat.
- Hard Red Winter Wheat: Provides a more robust, bread-like flavor, sometimes used in blends. Also called durum wheat, it is high in protein and gluten, good for bread and pasta. It can withstand harsher and more arid conditions. About 40% of the total US wheat production is hard red winter wheat.
Relative Prices of Whiskey Grains
In the chart below, you can see how prices fluctuate over time for the various grains. Corn is typically cheapest, followed by barley, and then wheat and rye are more expensive. Note that these are the overall commodity price per bushel (64 US pints) and specialty varieties will often cost significantly more.
Outro - Whiskey Grains
Each grain has something special to offer and the world of whiskey is vast! Make sure to try a variety of styles to find what you like. As time passes, don't be surprised to see more producers start to play with heirloom or specialty grains in the search for consumer excitement.