Enzymes are the unseen, underappreciated workhorses of distilled spirits. Yeast, distillation techniques, special ingredients, or unique barrels may be what get the spotlight, but without enzymes, a distiller is left with starchy, unfermentable mush.
Enzymes aren’t living organisms like yeast are, but they are a biological catalyst for reactions within living organisms or organic matter. There are thousands of known enzymes that help facilitate a wide variety of chemical reactions within all types of living things, from plants and animals to bacteria and fungi. They are molecules that act as keys, fitting into specific compounds to help—in the case of distillers as well as brewers—break them down into constituent parts.
Get to Know Your Enzymes
The primary enzymes that distillers rely upon are amylases, which break complex starches down into fermentable—or more fermentable—sugars, while a small group of secondary enzymes help improve processability and potentially provide for a slight boost in yield.
Cereal grasses such as barley, corn, wheat, and rye produce seeds that store energy in the form of starches—polymers of glucose molecules that require some effort or chemical intervention to access—to create a reservoir that the grain kernels can tap into when sprouting into the next generation of grain plants. Most of these starches are in the form of glucose chains, primarily chains of 1,4 linkages between any number of glucose molecules—with some amylopectin, containing a greater number of branches (1,6 linkages) in the glucose chain.
Malting barley and other grains takes advantage of their natural biological pathways, making these sugars available. Germination is the first stage of malting, where the grain kernels sprout and start down the path to growth. During that stage, barley kernels produce a variety of enzymes that eventually help a distiller or brewer unlock those sugars.
Alpha amylase and beta amylase occur naturally within malted grain, created in the kernel during germination (along with very small amounts of other enzymes required to help the grain sprout and grow into a plant). However, only in barley are they present in high enough concentrations to convert all the barley’s resident sugars; other grains lack enough naturally occurring enzymes to self-convert.
Producers of malt whiskey can lean entirely on these enzymes, especially on beta amylase, to convert their mash. Beta amylase operates at a lower temperature and provides a more complete breakdown of starches. Alpha amylase, meanwhile, will break down chains of amylose and amylopectin into shorter chains—severing 1,4 links at random—but will not convert those into a fermentable form.
Most yeasts will convert, in preferential order, glucose (a single glucose molecule), maltose (two glucose molecules), and maltotriose (three glucose molecules). A certain amount of balance is essential—yeast that feast on an overabundance of glucose may go dormant rather than tackling more difficult maltose or maltotriose, sometimes leading to stalled fermentations.
Beta amylase is most active below 150°F (66°C), generally around 143° to 149°F (62° to 65°C), and it will break down every other 1,4 bond to produce primarily maltose and a small amount of other fermentable sugars and dextrins—unfermentable groups, especially branched groups, of more than three glucose molecules. This produces a highly fermentable mash, leading to a higher-yielding spirit fermentation.
Alpha amylase, on the other hand, is most active at relatively higher temperatures—broadly, about 150° to 160°F (66° to 71°C)—and it doesn’t denature until about 165°F (74°C) or the mash pH drops too far. Because alpha amylase will break down starches into smaller pieces—cleaving 1,4 bonds at random and creating shorter but still unfermentable dextrin chains—it can be used in distilling to facilitate the initial gelatinization rest for grains such as corn and rye.
Enzymes Beyond Barley
Different grain starches gelatinize and become available at different temperatures. Barley’s gelatinization temperature conveniently overlaps with the lower end of its starch conversion, or saccharification, temperature. However, the starches in rye and corn require higher temperatures to break down their crystalline structures—usually about 180°F (82°C) at small distilleries, though large ones sometimes use a pressure vessel to accelerate the process at higher temperatures.
The change from raw to gelatinized starch is a familiar flavor transformation to anyone who has cooked polenta or grits—the milled corn tastes starchy during the initial stage of cooking, but it eventually transforms into something sweeter and more flavorful. (Sadly, our bourbon and corn whiskeys don’t come with butter and cheese, dressed with shrimp or pork belly.)
To help facilitate the transformation, distillers may use a premalt addition—malted barley that went into the high-temperature gelatinization stage and was quickly denatured, but not before contributing some alpha amylase activity to thin (liquefy) the mash. Those distillers focused on tradition then cool the mash below 150°F (66°C) before adding a second helping of malted barley to tap into the malt’s beta amylase.
In the past, the malt used for such a mash was made from six-row barley, high in enzymes but relatively low in starch. That was called distiller’s malt. Modern two-row malts have improved enough to take on that role while offering improved flavor and yield.
However, modern chemistry and biotechnology have brought an even more powerful tool to the table: exogenous enzymes, or those created outside the grain in the mash. These enzymes can augment or entirely replace the activity of traditional malt enzymes. They’ve opened the door for distillers to make whiskeys that were previously impossible—or at least grossly unprofitable—such as 100 percent rye whiskey. The distiller can simplify the mashing schedule and add malt at the beginning of a mash for flavor, rather than prioritizing conversion and yield concerns.
Labs generally produce exogenous enzymes by using bacteria. These include multiple members of the Aspergillus mold family as well as genetically modified or edited microbes, purified in an industrial lab setting. The enzymes produced include high-temperature alpha amylase, which can be added to a mash during gelatinization without becoming denatured, allowing for better liquefaction and easier processing. During the saccharification rest, distillers can rely on glucoamylase, aka amyloglucosidase. Active below 140°F (60°C), this enzyme will chew through every 1,4 and 1,6 linkage to reduce the entire available starch package down to glucose.
Along with addressing starch concerns, exogenous enzymes such as beta glucanase can help distillers make their mash easier to process. The starches in some raw grains are locked up in a matrix of beta glucans. In barley, the malting process breaks that down, while corn contains only nominal glucans. However, in rye, oats, and less-modified barley, the high levels of beta glucans can create a gummy mash that is difficult to transfer and is prone to scorching in the still. Also, because of beta glucans’ role in binding up starch in the raw grain, beta glucanase can free up small amounts of starch that remained bound up and unavailable for conversion.
Proteases, or protein-degrading enzymes, are another common group of exogenous enzymes. These help break down proteins in the mash to produce a less viscous mash and create free amino nitrogen (FAN), an essential nutrient for yeast fermentation. This may provide distillers an advantage, particularly when dealing with poorly modified malt or high-protein raw grain.
Proteases and glucanases tend to be lower-temperature mash additions, below 150°F (66°C) rather than during gelatinization. Along with both exogenous and endogenous amylases, they will stay active as long as the mash temperature doesn’t go above their denaturing threshold. They will remain active and continue working on small remnants of available starch, protein, or glucans even through the beginning of fermentation, but they become inactive once the pH drops too far. Depending on a variety of factors, including water chemistry and secondary microbial activity, the mash pH will generally go from the mid-5s to the low 4s or high 3s—and every enzyme has its own preferred range.
Whether or not they realized it, distillers have always relied on enzymes in some form or another. Their availability, variety, and efficacy have only increased over the years, offering opportunities for easier and more efficient mashes, and tools to help distillers better craft the spirit they envision.