Barley is the grain behind the vast majority of beer, but it’s far from the only one. Wheat, rye, oats, corn, rice, and a growing list of ancient and gluten-free grains all play roles in brewing, each contributing distinct flavors, textures, and fermentation characteristics. The grain (or combination of grains) a brewer chooses shapes nearly everything about the finished beer, from color and body to head retention and taste.
Barley: The Default Grain of Beer
Barley dominates brewing for a simple reason: when malted, it produces abundant enzymes that convert its own starches into fermentable sugars. No other grain does this as efficiently. Barley also has a husk that acts as a natural filter during the brewing process, making it practical to work with at scale.
There are two main types. Two-row barley has larger, more uniform kernels with a higher ratio of starch to husk, producing a cleaner, more neutral malt flavor. It’s the standard base grain for most craft and European beers. Six-row barley, by contrast, has smaller kernels packed with more protein and significantly more enzymes. That extra enzymatic power makes six-row popular with large North American breweries that brew with high proportions of adjuncts like rice and corn, since those grains lack the enzymes to convert their own starches. You’re unlikely to see a beer made entirely from six-row barley because the excess protein can cause haze, filtration problems, and off-colors. But six-row’s high protein content makes it ideal for specialty malts, where amino acids drive the chemical reactions that produce deep color and complex flavor.
How Malting Transforms Raw Grain
Raw grain can’t be brewed into beer on its own. It needs to be malted first, a controlled process of soaking, sprouting, and drying that unlocks the enzymes brewers depend on. During steeping, the grain absorbs water and begins to activate its metabolism. Over several days of germination, the grain produces amylase and protease enzymes that start breaking down starch into sugars and proteins into amino acids. The grain’s internal structure becomes fragmented and porous.
Kilning stops germination by drying the grain with heat. The temperature and duration of kilning determine the malt’s character. Gentle kilning at lower temperatures (around 100 to 140°F) preserves enzymes and produces pale base malts. Crystal and caramel malts are kilned at higher moisture levels, with temperatures raised to 150 to 170°F and held for about two hours. This effectively converts the starches to sugars inside the grain husk before drying, creating the sweet, toffee-like flavors found in amber ales and red lagers. At the extreme end, chocolate and black patent malts are roasted at 420 to 450°F for up to two hours, producing the deep bitterness and coffee-like intensity of stouts and porters.
Wheat: Body, Haze, and Foam
Wheat is the second most common brewing grain. Its high protein content produces the thick, long-lasting white head that defines styles like hefeweizen, witbier, and American wheat beer. It also adds a soft, bready mouthfeel and a light grainy flavor that can linger into the finish. Many wheat beers use 50% or more wheat in the grain bill.
Wheat doesn’t need to be malted to work in brewing. Unlike rice and corn, wheat starch gelatinizes at low enough temperatures to break down in a standard mash without special treatment. But wheat loses its husk during processing, which creates a practical problem: without husks to form a filter bed, the mash can clog. Brewers compensate by blending wheat with husked barley or adding rice hulls.
Rye and Oats
Rye gives beer a richer, spicier character than wheat, with a peppery bite that works well in saisons, roggenbiers, and rye IPAs. Even a small percentage in the grain bill adds noticeable complexity. Like wheat, rye is huskless and high in sticky proteins called beta-glucans, which can turn a mash thick and gummy if not handled carefully.
Oats contribute a silky, almost creamy mouthfeel. They’re a defining ingredient in oatmeal stouts and the hazy, juice-forward New England IPAs that have surged in popularity. Oats are typically used in smaller proportions, around 5 to 20% of the grain bill, and are often added as flaked (unmalted) oats for maximum texture.
Corn and Rice: The Light Lager Staples
Corn and rice are classified as adjuncts, meaning they supplement barley rather than replace it. Both are staples in mass-produced American and Japanese lagers, where they serve a specific purpose: boosting fermentable sugars while diluting color, body, and flavor. The result is a lighter, crisper, more neutral beer.
Rice provides a clean, dry finish with a flat sensory profile. Some rice malt beers show a slight vanilla note and pale yellow color, but the overall effect is restrained. This neutrality is exactly the point for brands aiming at broad drinkability, though it can make rice-heavy beers less interesting from a flavor standpoint. Corn adds slightly more character, contributing subtle sweet corn and popcorn-like aromas. Beer color drops by roughly one unit on the standard brewing color scale for every 10% of corn added to the grain bill.
Both grains require the enzyme-rich six-row barley (or added commercial enzymes) to convert their starches, since they produce very little enzymatic activity on their own. Rice and corn also need to be gelatinized, usually by boiling separately, before they can be added to the mash. Raw wheat can skip that step, but these two cannot.
Ancient and Heritage Grains
Craft brewers have increasingly turned to ancient grain varieties that predate modern agriculture. Spelt, emmer, and einkorn are all ancestors of modern wheat, and each brings a distinct personality to beer.
Spelt has a nutty, slightly spicy flavor that modern barley can’t replicate. Its kernels retain a tough, papery hull even after threshing, and those hulls act as a natural filter bed during lautering, helping prevent the clogs that plague wheat and rye mashes. Spelt runs 12 to 15% protein, which means more haze but also more body. Brewers typically use it at 20 to 30% of the grain bill.
Emmer tastes deeper and more bread-like, with a faint sourdough tang. Its protein content runs even higher, 13 to 17%, and it carries high levels of beta-glucans, long-chain sugars that can turn a mash viscous and difficult to work with. Einkorn is the most challenging of the three, with 14 to 18% protein, very high beta-glucan levels, and a dense, hard kernel that can strain a grain mill. But it rewards the effort with an earthy sweetness described as wet stone and honey. Mashing einkorn produces a thick, almost oily wort. All three ancient grains need a low-temperature rest early in the mash (around 95 to 110°F for 15 to 20 minutes) to break down those beta-glucans before they cause problems.
Gluten-Free Alternatives
For brewers working without barley or wheat, the options include sorghum, millet, buckwheat, rice, and pseudocereals like amaranth and quinoa. These grains make true gluten-free beer possible, but they come with significant brewing challenges.
The central problem is enzymes. Barley malt produces ample amylase to convert starch into sugar. Most gluten-free grains do not. Buckwheat malt, for example, has much lower amylolytic activity than barley, leading to low extract yields, high wort viscosity, slow filtration, and fermentation problems. In practice, brewing 100% buckwheat beer without adding commercial enzymes is extremely difficult. The resulting beer tends to be opaque and brown, with poor foam stability and a pronounced bitterness driven by high levels of phenolic compounds and flavonoids.
Amaranth faces similar issues: lower carbohydrate content, reduced enzyme capacity, and a higher gelatinization temperature that demands a specialized mashing process. Beers made from 100% amaranth malt have been described as slightly opaque with poor foam and an intensely bitter taste. Sorghum is probably the most commercially successful gluten-free base grain, widely used in dedicated gluten-free breweries, though it typically requires enzyme additions and careful process control. Most gluten-free brewers blend multiple grains and supplement with enzymes to get a balanced, drinkable result.
Why the Grain Bill Matters
Every beer style is defined in large part by its grain bill. A German pilsner built on 100% two-row barley malt tastes crisp and clean. A Belgian witbier with 50% unmalted wheat and a dose of oats has a cloudy, pillowy softness. A craft stout layered with chocolate malt, roasted barley, and flaked oats delivers coffee bitterness wrapped in a creamy body. The grain is doing most of that work before hops, yeast, or water ever enter the equation.
Soluble proteins from the grain influence foam retention, mouthfeel, and color development during the boil. When wort-soluble protein stays below roughly 5.5%, it contributes positively. Above that threshold, you risk excess color, filtration issues, and haze. This is why high-protein grains like six-row barley, wheat, and ancient varieties need to be balanced against lower-protein partners or used in styles where haze and body are welcome.