Malted grain is any cereal grain that has been soaked in water, allowed to partially sprout, and then dried with heat to stop the growth. This controlled process, called malting, transforms a hard, starchy seed into a softer, sweeter, enzyme-rich ingredient. Barley is the most commonly malted grain, but wheat, rye, oats, millet, and even corn can all be malted. The result is the foundation of beer and whiskey, a powerful tool in bread baking, and a more nutritious version of the original grain.
How Malting Works
Malting is a three-step process: steeping, germination, and drying (often called kilning). Each stage changes the grain’s internal chemistry in ways that make its starches accessible and its flavors more complex.
During steeping, raw grain kernels are submerged in water, sometimes for a day or more with periodic draining. The kernels absorb moisture, which wakes up the seed’s embryo and triggers the release of naturally occurring enzymes. These enzymes begin breaking down the protein and carbohydrate walls that surround the grain’s starch reserves, essentially unlocking the seed’s stored energy.
In the germination phase, the grain is spread out in a cool, humid environment and allowed to sprout. A tiny shoot (called the acrospire) begins to grow inside the husk. During this time, four classes of enzymes go to work converting the grain’s starch into simpler sugars: glucose, maltose, and maltotriose, among others. The grain also produces new enzymes that weren’t present in the raw seed. Germination typically runs for several days and is carefully monitored so the sprout develops enough to modify the starch but doesn’t consume too much of it.
Kilning is the final step. The sprouted grain is heated in a kiln to halt germination and lock in the enzymatic and flavor changes. Lower temperatures produce pale malts that retain more active enzymes. Higher temperatures create darker, more intensely flavored malts with rich caramel or roasted notes, though the heat deactivates some of the enzymes in the process. The entire malting cycle, from steeping through kilning, generally takes about a week.
What Changes Inside the Grain
Raw grain is mostly long-chain starch molecules packed tightly together, which is why uncooked grain is hard and not particularly sweet. Malting breaks those long chains into shorter sugar molecules that taste sweet and dissolve easily in water. When the malt is later mashed (soaked in hot water), these enzymes continue working, converting even more starch into fermentable sugars. A well-made malt yields at least 80% extractable material, meaning the vast majority of the grain becomes usable sugar and nutrients.
Malting also reduces compounds called phytates (phytic acid) that naturally bind to minerals like iron, zinc, and calcium in raw grain, making them harder for your body to absorb. In millet, for example, malting for 72 hours reduces phytic acid by about 24%, and extending germination to 96 hours cuts it by roughly 45%. This means the minerals already present in the grain become significantly more bioavailable after malting. Cereal grains naturally contain calcium, magnesium, potassium, phosphorus, and iron, plus B vitamins and vitamin E, so freeing up those nutrients is a meaningful benefit.
The protein matrix of the grain also gets partially broken down during malting, which is one reason malted grain is easier to digest than raw grain. The starch arrives in your gut in shorter, simpler forms, and the protein is already partially dismantled. This is why malted grain porridges have been used across cultures as early weaning foods for infants.
Why Barley Dominates
Almost any cereal grain can be malted, but barley has been the standard since at least the 17th century in Europe and North America. There are practical reasons for this. Barley kernels have a tough outer husk that stays attached during malting and later acts as a natural filter bed when brewers separate liquid from spent grain. Barley also produces high levels of the starch-converting enzymes that brewers depend on.
Maltsters look for specific quality traits: plump kernels, high germination rates, moderate protein content, and minimal broken or skinned kernels. Barley varieties bred specifically for malting (often categorized as two-row or six-row types) are selected to hit these targets. Wheat, rye, oats, and sorghum are also malted for specific products, including wheat beers, rye whiskeys, and gluten-free beers made from sorghum or millet. Early European settlers in North America even attempted to malt corn when barley was scarce.
Diastatic Power: Measuring Enzyme Strength
Not all malts are equally good at converting starch to sugar. The measurement that captures this ability is called diastatic power, expressed in Lintner units. It reflects the combined activity of the starch-degrading enzymes in a given malt sample. A malt with high diastatic power can convert not only its own starches but also the starches of unmalted grains mixed in with it, which is useful in brewing recipes that include raw oats, corn, or rice alongside barley malt.
Pale malts kilned at low temperatures retain the most diastatic power. Heavily roasted or caramelized specialty malts contribute flavor and color but have little to no enzyme activity left. Brewers and distillers blend different malts to balance flavor against the enzymatic horsepower needed to fully convert all the starch in a recipe.
Malted Grain in the Kitchen
Outside of brewing and distilling, malted grain shows up most often in baking as malt powder or malt syrup. These come in two functional types: diastatic and non-diastatic.
Diastatic malt powder still contains active enzymes. When added to bread dough, those enzymes break flour starch into sugars that yeast can eat, which speeds up fermentation and produces a faster rise. The extra sugars also caramelize during baking, giving the crust a deeper brown color and a richer, slightly sweet flavor. Bagels, pretzels, and artisan breads often rely on diastatic malt for these effects. If you use it, watch your dough closely, as it may rise faster than the recipe suggests.
Non-diastatic malt powder (or barley malt syrup) has been heat-treated to deactivate the enzymes. It adds the same sweetness and browning but won’t accelerate the rise. Bakers use it in place of sugar in recipes like hot dog buns or sandwich bread where malt flavor is the goal. Substituting one type for the other isn’t always straightforward: swapping diastatic malt into a recipe that calls for non-diastatic can over-convert the starch and create a gummy texture, while using non-diastatic where diastatic is called for will result in a noticeably longer rise.
Malted grain also appears in breakfast cereals, malted milk powders, and vinegars. Malted barley flour is sometimes blended into all-purpose flour at the mill to standardize enzyme activity and help commercial bakers get consistent results.
Malted Grain in Brewing and Distilling
Brewing is where malted grain plays its most essential role. The brewer crushes the malt and soaks it in hot water during a step called mashing. This reactivates the enzymes, which finish converting the remaining starch into a sugary liquid called wort. A typical wort is 70% to 75% fermentable sugars (mostly maltose, along with glucose, fructose, sucrose, and maltotriose), plus dissolved minerals, nitrogen compounds, and trace nutrients that yeast need to function. Yeast then ferments those sugars into alcohol and carbon dioxide.
The kilning temperature determines much of the beer’s character. Lightly kilned malt produces pale lagers and pilsners. Malt dried at higher temperatures yields amber ales and brown ales. Heavily roasted malt gives stouts and porters their dark color and coffee-like bitterness. Distillers follow a similar process but then distill the fermented liquid to concentrate the alcohol into whiskey, bourbon, or Scotch, each of which gets distinctive flavor contributions from its malt bill.