As a distiller, the decisions you make around grain-processing equipment can have significant impact on what you choose to produce—and vice versa.
Once you’ve got a handle on the principles of mashing and cooking, it’s time to look more closely at the physical design and operations of mash tuns, cookers, and related hardware.
Let’s Get Cracking
To begin with, spirits produced with a mash tun versus spirits that rely on a cooker require the grain to come into the system in a different physical form.
If you’re using a mash tun with the intent to run off a fermentable wort—separating the grain solids from the sugars, as is classically done in brewing and malt-whiskey distilling—you’ll need a roller mill to mill your grain.
The simplest design is the two-roller mill, which features a set of parallel metal cylinders designed to crush grain or malt kernels without pulverizing the hull. Then, those hulls can aid in running off, or lautering, the liquid fermentation media (or wort). More advanced versions of the roller mill include additional sets of rollers and, potentially, screens to divert larger particles toward further milling and the smaller particles away. This design lets a distiller optimize their grind for greater consistency and yield.
On the other hand, mashes processed in a cooker to be distilled and fermented on-grain—most commonly bourbon and rye—require a finer consistency in the size of the grain particles. Distillers achieve that consistency—closer to the texture of flour or grits—by using a hammer mill.
Hammer mills generally consist of a cylindrical screen with an array of hammers attached to a central spindle. Grain feeds into the center of the screen-hammer assembly, getting pulverized as the hammers spin around the screen and strike it, driving the smallest pieces through the screen and further downstream in the grain-handling system.
Whether you’re using a roller mill and mash tun or a hammer mill and cooker, you can optionally pre-mill the grain and store it in a hopper or grist case for future use. Or, you can mill on-demand with a system in which the mill feeds the cracked grain into an active mash vessel.
Grain, on the Move
There are a couple of popular options for conveying grain to or from the mill.
A bucket elevator is useful for vertical transport, and you can pair that with an auger. Distilleries commonly use bucket elevators with grain silos to elevate bulk grain so that it can drop down into the mill.
Once the grain is milled, two common options for moving it are flex auger or a chain-and-disc conveyor.
For a facility with enough space or a need to convey grain over long distances—some infrastructure or zoning regulations require milling to be at one end of the building and mashing at the other end—flex augers are the lower-cost option. Consisting of a motor-driven metal auger screw housed in a PVC tube, a flex auger is effective in elevating grain and transporting it horizontally.
One of the biggest limitations of flex augers, however, is their footprint when moving grain diagonally. Because the auger itself is a metal coil with considerable space for excess grain to fall through the center, flex augers are best used at angles lower than 45 degrees. If you need to lift your grain above a sizeable cooker or mash tun, you might run into space constraints in setting up a flex auger long enough to move grain efficiently. Flex-auger systems also can’t make hard turns that follow walls or wrap around corners; rather, they require gently curved PVC housing that prevents loss of efficiency.
A higher-cost option that addresses the limitations of flex augers is the chain-and-disc conveyor. A chain-and-disc system includes a series of pucks linked together with enough space between them for grain. The string of pucks fits into a tube that runs in a loop, rather than in a one-way, here-to-there system. The additional length—because of the half of the circuit that serves as the return—leads to higher equipment costs when designing and installing the conveyor. However, the system can run vertically, horizontally, and anywhere in between, and it can also incorporate right angles.
Mash Tuns and Cookers
Once you get the grain to its destination for starch conversion, the optimal vessel design and operation also depend on whether you plan to mash or cook.
In a traditionally run mash tun, the grain mixes with a portion of water, becoming hydrated as it enters the tun. To stir the mixture, the distiller runs an agitator or rakes as the mash is coming in but not necessarily when running off the wash or wort. (Some mash or lauter tuns are designed to run the rakes so that they can cut only the top of the mash, leaving the filter bed that the grain forms at the bottom undisturbed.) The sugary portion of the mash separates from the grain solids via a false bottom at the bottom of the mash tun or via a separate lauter tun—a vessel designed specifically for running off.
As the sugary liquid runs through the false bottom and out via a pump, it’s typical to sprinkle additional water on top of the mash. That additional water—sparge water, in brewing terms—rinses the remaining sugars out of the grain bed. Once the wort being collected drops below a certain concentration or reaches a desired volume, collection stops.
As in a mash tun, in a mash cooker, the water mixes with the grain as both enter the vessel. However, in most operations, the distiller adds all the water at the beginning, rather than an initial addition followed by a later addition via sparging. As usual, though, this isn’t a hard-and-fast rule—some distillers use a smaller amount of hotter water to reach their initial gelatinization temperature, then they bring in the remaining water cooler, to help bring their mash temperature down to saccharification temperature.
Unlike in a mash or lauter tun, where the bottom of the grain bed is undisturbed to help prevent solids from joining the liquid on its way out, the mash cooker contains an impeller or agitator that runs for the duration of the cook, helping to homogenize the mash. Mixing the mash helps to evenly distribute any enzymes added to encourage conversion, improves the dispersion of the heating or cooling, and prevents the mash from settling, which can create clogging issues when it’s pumped out of the cooker.
Once the cook is completed and cooled, you can empty the cooker and move the entire mash over to fermentation.
The Right Kit for the Right Fit
While the choice between different styles of spirits can be a complicated one that reflects a distillery’s ethos, marketing, and other factors, those choices also impact the potential equipment solutions available to a distiller.
Choosing the right grain-handling and mash-processing hardware for your desired portfolio is essential to bringing your vision to life.