When it comes to processing and mashing grains for whiskey, the distiller has a menu of options that can help add flavorful spins and touches to the final spirit’s character.
Whether it’s a mash of pure malted barley or a mixed grain bill of corn, wheat, rye, and the kitchen sink, adjusting that mashing process allows you to coax out different characters from the grains—plus, getting it right will set you up for success for all the processes that follow.
Here, we deal primarily with mashes composed of 100 percent malted barley—but much of this applies to mixed-grain mashes as well. First, however, we should sketch out how the process works, so that we can better identify where we can make meaningful adjustments.
When it comes to processing and mashing grains for whiskey, the distiller has a menu of options that can help add flavorful spins and touches to the final spirit’s character.
Whether it’s a mash of pure malted barley or a mixed grain bill of corn, wheat, rye, and the kitchen sink, adjusting that mashing process allows you to coax out different characters from the grains—plus, getting it right will set you up for success for all the processes that follow.
Here, we deal primarily with mashes composed of 100 percent malted barley—but much of this applies to mixed-grain mashes as well. First, however, we should sketch out how the process works, so that we can better identify where we can make meaningful adjustments.
[PAYWALL]
Calling Time & Temp
To get the most from our mashing process, we should first understand exactly what’s happening in there. The primary goal of mashing is to convert the cereal starches into fermentable sugars so that yeast can turn them into alcohol. Secondary goals include developing flavor and extracting nutrients that help the yeast complete fermentation.
To accomplish all this, a few things must happen. First, we need to make the starch in the grain accessible—we typically do this by milling the grain through roller mills of various sizes. The aim is to make the starch accessible and to increase surface area exposure for water and enzymes alike. Having the starch exposed to an aqueous mash system allows for the second necessary process to take place: gelatinization.
Gelatinization occurs once we’ve introduced our milled or broken-down grain to our mashing vessel and mixed it with water. Water penetrates the starch granules, forcing them to swell. Eventually, the various amylopectin and amylose components of the granules begin to unravel, leaching into the surrounding water and forming a gel. (This is a gross oversimplification of the process—I could go into much more detail, but it’s not exactly riveting reading unless you’re a cereal chemist.)
Once that gelatinization occurs, enzymes can convert the starch into fermentable sugars. This saccharification temperature is often around 147°F (64°C); depending on the thickness of the mash and total enzyme load, this might take less than 20 minutes. However, many distillers (including me) tend to go longer—30 to 45 minutes—to be on the safe side.
Without a doubt, this saccharification rest is the most important temperature when it comes to our ability to produce alcohol. But it’s not the only one.
During mash-in, when you’re adding grain to the brewing water, some distillers prefer to keep initial water temperatures low and heat everything as a whole, rather than mixing the grains with preheated water. The subsequent heating of the water and grain mix often takes a little more time, but these lower-temperature grain infusions have their merits. At 122°F (50°C), grain peptidases are quite active, and those help break down the protein matrices that surround the starch granules. It’s a nice benefit when you’re working with high amounts of poorly modified grain. Bonus: The protein breakdown releases amino acids into the wort, and those serve as yeast nutrients.
Another mash rest that some distillers have been exploring recently is the ferulic-acid rest. The aim of this rest is to increase levels of ferulic acid, which can then convert to 4-vinyl-guaiacol (4VG) during fermentation. An aromatic compound, 4VG is known for its spicy clove character. Generally, distillers who use a ferulic-acid rest to encourage 4VG tend to be working with malted wheat and/or malted rye. If you’re interested, a 15-minute rest at 113°F (45°C) should do the trick.
The Levers of Wort Separation
After the mashing process converts the starches to fermentable sugars, the next step in single-malt mashes is generally to separate the grains from the sweet liquid, or wort.
In a traditional mash or lauter vessel, the grain sits atop a perforated deck above a false-bottom cavity. Liquid sinks through the grain and perforated plates into the false bottom, and from there we can send it through a heat exchanger and into the fermentor. Meanwhile, we add more water atop the grain to further rinse out any lingering fermentable sugars.
If you brew beer, this all sounds par for the course. However, when you’re producing spirits, it’s within this seemingly simple operation of wort separation that we can have some of the biggest impacts on character. To understand how, we first need to understand the usual separation methods.
In the world of single-malt whiskey, there are two commonly employed ways to separate wort using traditional vessels. The first is what I call continuous sparging, or what some folks refer to as “fly sparging.” You continuously spray (or sparge) water onto the grain bed at a flow rate that roughly equals that of the wort draining out of the mash/lauter tun below. Once the emerging wort drops below a predefined specific gravity, or the pH begins to rise, wort collection stops. That’s how most craft brewers approach the process, and it works well—when properly managed, it produces a clear wort with little in the way of residual grain solids going into the fermentor.
The second method is more commonly used in making Scotch, and it roughly equates to what many homebrewers refer to as “batch sparging.” In this process, once the saccharification rest is complete, you drain the sweet wort from the lauter tun completely and, often, rather quickly. Then you add a “second water”—at roughly a quart per pound of grain, or two liters per kilo—at 176 to 194°F (80 to 90°C), allowing it to briefly settle before draining and mixing with the initial strong wort, now in the fermentor. You then add a third water, twice as much as the second, and again let it settle and drain—but this time, the weaker wort goes to a separate buffer vessel, where it sits until it’s ready to be used as the mash water for the next mash.
Both methods have their adherents and opponents. I’ve always been partial to the continuous method because it allows me to more easily get a clear wort. Others prefer the expediency of the Scottish method. However, it’s important to understand where the flavor drivers are for each method.
The temperature of the sparge water is important. Generally, the hotter the temperature, the more efficient your extraction—but that may come at the cost of extracting higher amounts of phenolics and fatty acids. That’s not necessarily a bad thing if that’s your aim, but you should be aware. The fatty acids may esterify over time, but it could take years before the chemical dust settles.
The other thing to watch is wort clarity. Many single-malt distillers these days play a bit with cloudy worts. These worts have higher amounts of grain solids and particulates in them. Once fermented and distilled, the resulting new-make spirit fittingly has more cereal and malt notes. It may also contain higher amounts of esters and fusel oils. Contrast that with the production of distillate from clear wort, and you’ll find them to be very different beasts indeed. Clear worts tend to produce distillates with far less cereal character and lower ester levels.
Neither point of view is better than the other, but they produce different results. Often, distillates from cloudy worts require more time in the cask before the new-make spirit character settles down to an acceptable level. Conversely, pristinely clear worts may be ready for prime time a bit sooner, but they also may lack some complexity in the final spirit (making cask selection for these spirits a lot more important).
Mashing as an Opportunity
If you work in a whiskey distillery, you might take the mashing process somewhat for granted. After all, when it comes to developing flavor in the final spirit, most distillers are agonizing over grain selection, yeast strains, distillation techniques, and barrel choice. Hell, even bottle proof gets more attention than mash technique. I think this is because, as distillers, we tend to think of mashing as a mere means to an end: fermentable sugars, and nothing else.
Honestly, it’s a shame that we give mashing so little thought. It has more impact on our flavor profile than we often give it credit for. And the potential for experimentation with different rest temperatures and wort clarities makes for another interesting process point where you can place your mark as a distiller. Perhaps the effects will be subtle and nuanced, but sometimes a little nuance is all it takes to lift a spirit from good to great.
