Planning a whiskey mash can be a formidable task.
First, you need to decide on the style and desired flavor profile. Then—with pencil to paper and a good eraser—you scuttle through countless variations of recipe percentages. That’s all before you even make the first batch, which will take months or years before you figure out whether the recipe is any good.
It is a precarious position for any distiller. But have heart! It’s all in the name of your craft. Your art! Surely, it’ll all be okay … right?! (On second thought, maybe 0.7 percent more rye would be better, and let’s add a little wheat in there for good measure, and what about that heirloom corn grown by that farmer down the road …)
Sorry, I can’t help you with any of those details. What I can do is help you understand the underlying calculations to help you decide how much grain you’re going to need—bean-counter stuff. This is important if you plan to make any money. In fact, even if your recipe is 100 percent malt or rye or corn or whatever, these calculations will help you dial in your efficiencies, so that you’re maximizing your production time and producing the best spirit possible. Even the bean counters will be happy about that.
[PAYWALL]
Defining the Variables
To make the math sensible, we need to define a few things.
The first one is the amount of extract you expect to get from your grain. Extract is the amount of starch (and smaller amounts of sugars) that your grain will theoretically offer up to your mash vessel and the fermentation gods.
You should receive specs—a certificate of analysis (COA)—with every order of grain. (If you don’t, ask your supplier—they’ll be happy to oblige. And if they aren’t, find a new grain supplier.) On that COA, you’ll see a listing, or a set of listings, for extract. Often the term “extract” is followed by the phrases “coarse grind” or “fine grind.” Course grind refers to grain that has been run through a mill with a 0.7-millimeter gap setting. This is the type of grind more akin to a standard single-malt production facility using roller mills. The fine grind refers to grain that has been run through a mill with a 0.2-millimeter setting, which is closer to a meal consistency, or even flour. The fine-grind value is often used in distilleries with hammer mills, such as many American whiskey operations. You’ll need to make the call on which method more closely resembles your own distillery procedures. (If you’re unsure, I suggest erring on the conservative side—first try the coarse-grind value.)
Another word on extract: Most grain spec sheets list extract on a dry-weight basis, or dwb, which is, in my humble opinion, incredibly annoying. Whether it be the 12 percent moisture often found in field corn or the 4 to 6 percent moisture in most distiller’s malts, the dry-weight values lack real-world accuracy for the distillery—the moisture inside the grain throws that number off. That means that if you took the dry-weight extract value and used it in the upcoming recipe calculations, your results would be frustratingly different from what your actual mash would tell you.
Fortunately, there’s an easy solution. We can convert the dry-weight extract to as-is extract, which accounts for the moisture and offers a much more accurate prediction of how a grain will behave in your distillery.
To convert dry weight extract values to as-is values, simply use the following formula:
Figure 1
For example, let’s say we have a grain with an extract value of 81 percent, dry-weight basis, and it has a moisture content of 6 percent. The equation would look like this:
Figure 2
Regardless which value you use, understand that the extract number listed is the theoretical maximum amount of fermentable extract you can hope to obtain from proper mashing procedures. The truth is that distilleries rarely hit those theoretical values. Because of variances in technique, equipment, employee hangover severity level (EHSL), Saturn’s alignment with Venus, and so on, most distilleries hit anywhere from 85 to 95 percent of those listed extract values.
Whatever the decrease from the theoretical extract may be, that is your mash efficiency (ME) value, an important number to remember—and to constantly aspire to beat. In general, on-grain fermentations—as commonly done for bourbon, rye, and other American-style whiskeys—have mash efficiencies between 90 and 98 percent. Single-malt producers who practice off-grain fermentations by lautering and separating the grain from the sweet liquid wort after mashing tend to have lower efficiencies—from 85 to 95 percent. (There are bits of equipment that will dramatically increase mash efficiency in single-malt distilleries, such as wet mills and mash filters, but they are beyond the scope of this article.)
Of course, if you’re reading this and asking, “Hey, I’ve got a new distillery and haven’t gone through startup yet. How do I know what my mash efficiency is?” Once again, I suggest erring on the conservative side. Choose a lower number to start. After a few weeks of production tweaks and some back-calculations, you should get a decent idea of what the true value is for your system.
Building the Recipe
Now, back to the question at hand: How much grain will you need for your recipe? To figure that out, let’s begin with an imaginary distillery and mash bill.
Let’s say we want to produce a bourbon that’s 70 percent corn, 20 percent rye, and 10 percent malted barley. We’re going to make 1,000 gallons of mash for an on-grain fermentation/distillation, and we normally get a mash efficiency of 95 percent with our system. Finally, let’s say we have a target starting gravity for our mash of 1.072 (17.5° Brix).
Now that we’ve set the scene, we can begin digging into our COAs to figure out the extract potential we can expect from our corn, rye, and malt. Let’s say our grain suppliers have given us the following specs for our grains:
Figure 3
First, we need to convert all our extract data from dry-weight basis readings to their more accurate (for our purposes) as-is values. Using the formula in Figure 1, we get the following extract values:
Figure 4
We now have all the data we need to find the required weights in our recipe. The only missing component is a formula into which we plug all that data. Well, here you go:
Figure 5
Here, gravity points simply refers to the difference in specific gravity between our recipe and water. In this case, we stipulated that our recipe should have a starting specific gravity of 1.072, which is 72 points over water’s specific gravity of 1.000. Therefore, we have 72 gravity points.
The recipe volume is simply your desired volume of finished wort—in this case, 1,000 gallons.
You’ll also note that there is a constant in the denominator. Distillers have arrived at the value of 46.31 (or 386.5 for metric users) over years of fine tuning. The origins of these constants fall outside our scope here—maybe we cover that in a future article, but for now you just need to memorize it (or write it down somewhere handy).
The next piece of the puzzle is the actual extract (AE) contributed by each individual grain. Remember, our mash system isn’t 100 percent perfect, so we won’t recover every last bit of extract from our grain. We do need take our system’s mash efficiency into account for all our grains.
If we were working with a single grain, the actual extract is fairly simple to calculate: We multiply our grain’s as-is extract value by our mash efficiency, and that will give us a relatively accurate idea of the total extract we should obtain from our grain in the mash.
In this scenario, however, we’re working with three grains—so, what do we do? Don’t worry, it’s not that hard—all we do is multiply each of our individual grain extract values by our mash efficiency. Let’s see how that looks:
Figure 6
Now we just calculate the value for the total extract our grain contributes to the system. This, too, is incredibly simple: We just multiply each grain’s own actual extract value by its recipe percentage. Then, we add all three values together to get the total extract for our mash:
Figure 7
From here, the solution to our question of how much grain we need is a basic “plug and play” operation. Our final equation looks like this:
Figure 8
So, our recipe requires a total grain weight of 2,429.3 pounds. From here, just multiply the total grain weight by the recipe percentages to get the individual grain weights required:
Figure 9
Why We Do the Math
Okay, I know what you’re thinking: “That’s a lot of math to figure out something I can probably find an online calculator to do for me.”
Sure, there are brewing recipe calculators online—no need to sully your hands with a pencil’s graphite. The problem is, in my experience, they’re not especially accurate for distillers. More importantly, I find this method helpful because it forces us as distillers to look more deeply under the hood of our individual recipes—it helps us to better understand how it all works. Plus, once you understand a recipe’s fundamentals, it becomes immensely easier to make adjustments as needed.
These calculations also allow you to back-calculate your mash efficiency (among other things). When it comes to your distillery’s bottom line in the production space, mash efficiency is an important number. Let’s say you continue to twist the proverbial dials in your distiller’s toolkit, and after a few weeks you begin to see your starting gravity rise from 1.060 to 1.070. You can easily calculate your new mash efficiency. Once you know that, you should have a good understanding of whether you’ve hit the ceiling of possible efficiency or whether there’s more extract that you’re potentially missing.
Learning how to calculate recipes by hand can be a game-changer. Understanding the math can lead to a much deeper understanding of your grain and how your equipment works. You won’t be flying blind, and you can start planning a road map to improve how you manage your mashes and recipes.
Putting in the effort on a small amount of math will be well worth it in the end—for your whiskey, and for your distilling business.
