During presentations on liquor distillation, I’m often asked why we mash grain into hot water to produce a wort that’s further fermented into a wash, and then distilled to make flavored spirits, such as whiskey and brandy. If you’re mashing the grain to produce fermentable sugars, the argument goes, wouldn’t it be more efficient and simpler to dissolve sugar in water and go from there? If it were simpler and cheaper than using grain, then commercial distilleries would be doing just that. After all, they’re in business to make a profit, so why wouldn’t they use the cheapest, easiest process possible? But there’s a sound, scientific reason for beginning from grain to distill alcoholic beverages.
Some commercial liquor, particularly inexpensive, mass-produced vodka, is fermented and distilled from sugar derivatives, such as molasses, but making whiskey requires a different type of distillation. Vodka is a flavor-neutral spirit, unlike whiskey, rum, and brandy, which are flavor-positive spirits. Some of the flavor in finished spirits results from their particular distillation process, and even the type of still used to produce them. But much of the flavor profile comes from the grains: their malting process, their extraction through the mashing process, and partially via fermentation.
For our purposes here, we’ll be discussing how to optimize your flavor just during the step of fermenting grain into a wash, which follows the grain mashing and precedes the distillation and aging process. After the grain has been mashed and heated in water, it’s either strained out or left in, depending on the type of whiskey, leaving you with a wort you can then ferment. Most types of American whiskies are fermented with the mashed grains left in. On the other hand, the wort is generally drained off before fermenting malt whiskies and Irish whiskey. It seems the reason for keeping the grains in during fermentation — especially with bourbon, as corn has a lot of fermentable sugar — is to maximize the extraction of fermentable sugars, as well as for specific flavor nuances of the particular grains used.
Mash, Wort, Wash
The terms for each step of the process for making beer, whiskey, and other spirits are sometimes unfamiliar. Here’s a short glossary to guide your reading.
- Mash: The first step in both beer brewing and other alcoholic beverages. Malted (germinated and dried) or milled (mashed or crushed) grains are soaked in warm water. The diastatic enzymes go to work on the starches in the grains, converting them to fermentable sugar. As starches convert to sugars, the sugars are released into the mash water.
- Wort: The residual sugary liquid of a mash is called a wort. If you’re making beer, the wort is drained off of the grain, then boiled, usually with hops added during the boiling stage, and later, yeast is added to begin fermentation; for distillations, sometimes the grain is removed from the wort, and other times it’s simply cooled before yeast is added for fermentation.
- Wash: The wash is a cooled wort to which yeast has been added, and then fermented. A wash is ready to boil in the still and begin distillation.
Nourish Your Yeast
Creating a wash begins with the addition of yeast to the wort. In order to grow and multiply rapidly, yeast needs nutrients, such as amino acids and nitrogen, which are present in grain and the subsequent mash. If you’d started by fermenting pure sugar dissolved in water, you’d have to add large amounts of yeast to compensate for the lack of nutrients in the wash. Furthermore, the yeast simply wouldn’t need to multiply as much if there were already sufficient yeast cells present to ferment the available sugars. Under these conditions, with no added yeast nutrients, you’ll rarely end up with a wash of more than about 8 percent alcohol by volume (ABV) before the yeast dies off and stops fermenting. This isn’t efficient.
Yeast is first added into wort, where it rapidly multiplies, utilizing sugar to form more yeast cell material. This is the aerobic stage of fermentation, where oxygen is required. Then, the yeast stops multiplying when all the dissolved oxygen in the mixture has been consumed. Finally, the yeast enters the anaerobic stage, further converting the sugar to alcohol and carbon dioxide.
Once fermentable sugars are used up, the yeast metabolism changes, breaking down and consuming non-fermentable sugars and other organic compounds. If this begins to happen in your ferment, the yeast will metabolize enzymes such as permease from the non-fermentable sugars, which leads to the formation of undesirable flavors. This can be avoided, however, by adding glucoamylase enzymes to ensure a minimum of non-fermentable sugars.
Yeasts and Yield
The type of yeast you use affects the alcohol yield, as well as the rate and intensity of the fermentation process, and ultimately contributes to the creation of a complex flavor profile. Some hobby distillers advocate using huge amounts of yeast, suggesting that it doesn’t hurt, and may result in increased alcohol production. The popular “turbo yeasts,” highly alcohol-tolerant yeasts with added nutrients in their makeup, are typically formulated to ferment 11 to 17.6 pounds of sugar dissolved in 25 liters of water. This generally results in a wash of 13 to 20 percent ABV. These yeasts are best utilized for making gin or vodka, if you want to make those from sugar and water. However, turbo yeasts aren’t useful for grain-mash fermentation. Alcohol-tolerant yeasts, such as turbo yeast and champagne yeast, aren’t suitable for producing desirable flavors in whiskies.
In my experience, about 5 grams of yeast (1/4 teaspoon) per liter of wash is plenty. Overdoing the yeast is wasteful at best, and can adversely affect the flavor of some spirits, especially whiskey. Yeasts specifically made for distilling tend to be highly attenuated, meaning they produce a low-sugar wash — and thus, a low specific gravity — at the end of fermentation. Experiment with different strains of beer yeasts, made with at least 2 liters of starter, to find the best ingredient amounts.
Yeast Starter Recipe
Check the specific gravity of your wort with a hydrometer. If your wort is high in sugar — with a specific gravity of 1.070 or more — use a yeast starter. Those poor little yeast cells can be overwhelmed in the presence of such an abundance of sugars, and may die out before all the sugar has been converted to alcohol. The starter helps to increase the number of yeast cells before adding the yeast to the fermenter, thereby jump-starting the fermentation process. You can also try making a yeast starter to “proof” yeast that’s past its use-by date. Some yeast cells will still be viable up to about a year, so it’s worth trying. However, it’s best to always use fresh yeast, so don’t buy more than you need at one time.
- 1 to 2 pints fresh wort at room temperature
- About 2.5 grams yeast per pint of wort
- Using a glass or translucent plastic container, pitch (add) your yeast into the wort, shake well, and let sit for one or two days.
- After a day or so, you should begin to see layers of yeast sediment at the bottom of the container, at which point you can add the starter to the wort in the fermenter.
From Wort to Wash
After you’ve made a yeast starter, put the fermenter in a place where it can be left undisturbed for at least three days, ideally at an ambient temperature between 70 and 90 degrees Fahrenheit. Combine the entire contents of the wort, along with the yeast starter, in the fermenter. Begin the fermentation process by adding 5 grams of yeast per liter of wort, as well as enzymes, if you’re using them. After about 30 minutes, when the yeast is hydrated, stir the wort.
Malted grain undergoes a mashing process, creating a wort to which yeast and/or bacteria is added.
Fermentation usually slows after about 36 hours, and most distilleries stop fermentation after 48 to 60 hours, depending on what type of liquor is being made. Unlike the process of making beer or wine, where the wash typically undergoes both a primary and secondary fermentation, a wash that’s distilled goes through only primary fermentation. A secondary fermentation would adversely affect the ester profile of the wash, resulting in unpleasant-tasting liquor. As fermentation progresses, the wash acidifies, eventually lowering its pH to about 3.5. This helps control the growth of unwanted bacteria, which can’t survive in such an acidic environment.
Adding Flavor with Bacteria
Once you have a little experience with grain fermentation, diversify your flavor profiles by experimenting with bacteria. It’s less common, but nonetheless interesting and fun to try. When the acids produced from yeast and bacteria bond with alcohol, they create esters, and thus “esterify” into a wide variety of flavors with fruity and floral notes. For example, lactic acid esterifies with ethanol into ethyl lactate, which tastes like butter cream. This bonding process happens during all stages of liquor production. Different yeast strains produce different ester profiles during fermentation, just as in beer production, and free acids in solution eventually form additional esters during the aging process of spirits, such as whiskey and brandy.
Finally, after fermentation and distillation, the golden whiskey reveals its grain-infused flavors.
Lactobacillus bacteria are most active at the beginning and end of fermentation, because bacteria are already present in the air and on the grain you use. Some lactobacillus bacteria, for example, produce lactic acid, while other strains produce other kinds of volatile acids when they consume sugar during fermentation. It’s more or less dormant during the anaerobic phase, when yeast is most active. However, L. thermophilus, a heat-loving bacteria, survives the heat of fermentation during sugar conversion and continues to multiply. Its reproduction slows down as the pH of the wash drops, but it becomes more active as the yeast cells start to die. At this point, the lactobacillus consumes nutrients in the yeast sediment and any residual sugar it finds. As it eats, it begins to produce the acids that will later form esters.
Free acids are found in oak aging barrels, as well as in the various yeasts and bacteria naturally present in the wash. But you can also add the bacteria to your wash when you pitch the yeast; try different strains for making cheese and yogurt. Or, try adding bacteria several hours before adding the yeast. They will produce different acids, and therefore different esters, depending on the phase of fermentation.
As you can see, grain fermentation is fairly involved at the microscopic level, and yet relatively simple to achieve, once you understand the basic concepts. Be sure to keep notes as you experiment! When you create a particularly yummy beverage — and you will, I promise — you’ll want to duplicate it.
For more information on making malt whiskey:
Victoria Redhed Miller lives on an off-grid farm in northwest Washington state. She’s a regular speaker at the Mother Earth News Fair, and is the author of 3 books, including the award-winning Craft Distilling: Making Liquor Legally at Home.