Diastatic power is a measurement of how much enzyme activity a grain or malt has to break down starch into fermentable sugars. It matters most in brewing and baking, where those enzymes determine whether starches convert properly into the sugars that yeast needs to do its job. The higher the diastatic power, the more starch-converting capability the grain brings to the table.
How Diastatic Power Works
When grain is malted (soaked, sprouted, and dried), the sprouting process activates enzymes inside the kernel. Three enzymes do the heavy lifting: one chops long starch chains into shorter fragments, another clips those fragments into simple sugars like maltose, and a third breaks apart branching points in the starch molecule that the other two can’t reach. Diastatic power reflects the combined strength of all three.
The key word here is “active.” Heat destroys these enzymes. A lightly kilned pale malt retains most of its enzymatic punch, while a darkly roasted malt has had its enzymes cooked away. That’s why color and diastatic power tend to move in opposite directions: the darker the malt, the lower its converting ability.
How It’s Measured
In the United States, diastatic power is expressed in degrees Lintner (°L). A malt needs roughly 35 °L to convert its own starch without help. Base malts, the workhorses of a grain bill, typically sit well above that threshold. Briess Two-Row Malt and Briess Pilsen Malt both come in around 140 °L, giving them plenty of surplus enzyme activity to convert not just themselves but additional grains that lack enzymes of their own. A moderately roasted grain like Munich Malt (10L color) drops to about 40 °L, barely enough to self-convert and with almost nothing to spare for other grains in the mix.
Outside the U.S., you’ll sometimes see diastatic power reported in Windisch-Kolbach units (°WK), which use a different scale. The conversion is straightforward, but for most practical purposes, Lintner is the standard you’ll encounter in recipes and malt spec sheets.
Why Brewers Care About It
During mashing, crushed grain is mixed with hot water so the enzymes can convert starch into sugar. That sugar-rich liquid becomes the base of beer. If your grain bill doesn’t have enough total diastatic power, the conversion stalls and you’re left with unconverted starch, which means less alcohol, less body, and potential haze problems in the finished beer.
The practical minimum for a mash to fully convert is about 30 °L as a weighted average across all grains. Calculating that average is simple: multiply each grain’s diastatic power by its weight, add those numbers together, then divide by the total grain weight. If you’re brewing with a large proportion of specialty malts, crystal malts, or unmalted adjuncts (rice, corn, oats), those ingredients contribute zero or near-zero diastatic power while still adding starch that needs converting. Your base malt has to carry the load for everything in the mash.
This is why recipes heavy on adjuncts or dark malts often call for six-row barley or extra pale malt. Six-row varieties historically have higher diastatic power than two-row, giving brewers more enzymatic headroom. If you run the weighted average and land below 30 °L, adding a few more pounds of a high-enzyme base malt solves the problem.
Diastatic Power in Baking
Bakers encounter diastatic power most often through diastatic malt powder, a finely ground malted barley with its enzymes still intact. When added to bread dough, those enzymes break flour starch into sugars that feed the yeast. The result is a faster, more vigorous rise along with deeper color and more complex flavor in the finished loaf. Many commercial bread flours already contain a small amount of diastatic malt for exactly this reason.
The recommended starting point is 0.25% of total flour weight, and most bakers stay between 0.25% and 1%. Going higher risks trouble. Too much enzyme activity breaks down so much starch that the crumb turns gummy and unappealing, a problem that’s difficult to fix once it happens. Start low and adjust upward in small increments.
Non-diastatic malt powder looks similar but has been heated enough to deactivate its enzymes. It adds sweetness and color to baked goods without affecting the rise or crumb structure. Barley malt syrup, often used in bagel boiling water, falls into this same category: it creates an amber, shiny crust but doesn’t change how the dough ferments. The distinction matters because swapping one for the other in a recipe will give you noticeably different results.
The Falling Number Connection
In commercial flour milling, enzyme activity is often measured using a test called the Falling Number. This test drops a plunger through a heated flour-and-water mixture and times how long it takes to fall. High enzyme activity breaks down starch quickly, thinning the mixture so the plunger drops fast, resulting in a low Falling Number (below 100 seconds). Low enzyme activity leaves the mixture thick and viscous, producing a high Falling Number (above 200 seconds).
Falling Number and diastatic power are related but not identical measurements. Falling Number reflects starch properties as well as enzyme activity, so two flours with similar diastatic power can produce slightly different Falling Numbers depending on their starch granule size and structure. Still, the practical takeaway is the same: adding malt with higher diastatic power to flour lowers its Falling Number by increasing starch breakdown. Research on rye flour found that a small amount of high-activity malt (0.5%) produced the same effect as a larger dose of lower-activity malt (1.5%), so both the potency and the quantity of the malt you add determine the outcome.
Choosing Grains and Malts by Diastatic Power
For brewers building a grain bill, the simplest approach is to start with a base malt that has at least 120-140 °L and use it as the majority of the recipe. That gives you a comfortable enzyme surplus to handle 20-30% specialty grains without worrying about conversion. If you’re pushing specialty grains past 40-50% of the bill, run the weighted average calculation before you brew.
For bakers, the choice is more binary. If you want enzyme activity to improve rise and browning, use diastatic malt powder in small, measured amounts. If you just want malt flavor and color, use non-diastatic malt powder or barley malt syrup. Mixing them up is one of the most common mistakes home bakers make with malt products, and it leads to either flat bread (when you expected a boost) or a sticky, collapsed loaf (when you added too much enzyme activity without realizing it).