Malt Enzymes in Brewing (I Promise It’s Interesting)

By David Nilsen

In this recent blog post, we talked about the basics of brewing malt. But what does it mean that barley has been malted? It begins with natural processes in a grain of barley that are accelerated by the maltster—the person who turns barley and other grains into malt—and concludes with the variety of ways the maltster then halts those processes.

To understand malting, we have to talk about enzymes.

When I start to talk about enzymes during a beer event, I can sometimes see attendees begin to check out a bit, because even the word “enzyme” sounds hopelessly complex and scientifically abstract. In reality, the basic function of any individual enzyme isn’t that hard to understand. 

Enzymes are intricately folded, three-dimensional protein molecules that facilitate biochemical processes within an organism. Because of their dynamic role in living processes, it can be easy to think of them as microorganisms themselves, but they aren’t alive—they just exist as part of larger organisms. Each enzyme generally performs a single task on a single material (or “substrate”) and is helpfully named after the substrate it works on. Proteases work on proteins and cellulases on cellulose, for example. 

Enzymes are protein molecules folded into specific, three-dimensional shapes. That shape allows them to interact with and modify the structure of another substance at the molecular level, but prevents them from interacting with molecules of a different shape. You can think of each type of enzyme as a three-dimensional key that will fit a specific lock but won’t fit another. 

Every living organism has a large variety of enzymes that allow basic cellular and biochemical processes to occur. In barley and other grains, some of those enzymes perform roles that allow an individual grain—or seed—to produce a new plant.

Plants produce energy through photosynthesis, which requires sunlight. When a seed begins growing under the soil, however, it doesn’t have access to sunlight, so it needs a reserve of energy to fuel the plant until it can break through the soil. Most of the bulk of a kernel of grain is comprised of carbohydrates that provide that fuel.

The seed will ultimately need those in the form of simple sugars in order to use them, but sugars aren’t a great long term storage solution for a variety of reasons, so that fuel is locked up in a complex starch matrix held inside small pockets within the grain’s endosperm. It’s a stable storage system that can wait for months or even years for the right conditions, and once the right temperature and moisture conditions are met, enzymes are the keys that unlock that storage system. Plant hormones within the grain stimulate the production and release of enzymes that will turn that starch reserve into usable fuel. Hemicellulases and beta-glucanases break down the dividing membranes, proteases convert proteins into peptides and free amino acids, and amylases and dextrinases begin turning starch into sugar.

When it comes to producing malt for brewing beer or certain spirits, a maltster manipulates those temperature and moisture conditions to stimulate the development of those enzymes, because we’ll need them for the brewing process. Proteins need to be reduced, starch reserves need to be exposed, and, ultimately, starch needs to be converted into simple sugars like maltose in order to be fermented by brewing yeast.

After a few days under the right hydration and temperature conditions, the grain’s internal structure has been sufficiently modified to allow it to be brewed with, and at this point the maltster wants to halt the process, because otherwise the grain will do what it was supposed to do and grow a new barley plant. We don’t want a new barley plant, we want beer.

The maltster halts the modification process by drying the malt out before all the starch is converted into sugar so the brewer can finish that conversion during the brewing process.

Inside a vessel called a mash tun, the brewer mixes their malt with hot water, generally around 150° Fahrenheit. Over the course of about an hour, the diastatic enzymes developed during the malting process break down the malt’s starches into simple sugars in a process called saccharification. The primary enzymes at work—alpha and beta amylase—work in complementary ways to break apart amylases and amylopectins into mostly maltose and a few other simple sugars.

Curiously, these two enzyme groups favor slightly different temperature ranges. Adjusting the temperature of the mash just a few degrees can favor one or the other of these enzymes and affect the amount of fermentable sugar in the resulting wort (which is what we call the sugary, malty liquid that comes from the mash and will be fermented into beer). Slightly lower temperatures favor beta amylase, and slightly higher, alpha amylase. Mashing in beta amylase’s preferred range will lead to more fermentable sugar and a drier-bodied beer, as more of the malt’s sugars will be fermented away. Mashing in alpha amylase’s preferred range will do the opposite. The brewer will choose a temperature, or—in some cases—a series of temperature rests, to achieve the results they’re looking for.

In order to brew, you need malt, and in order to make malt, you have to trick grain into trying to grow a new plant.  Except in this case, we’re “growing” a future pint of our favorite beer.

You can learn more about the basics of beer in this episode of the Bean to Barstool podcast: