Sweet Mash Bourbon: Going Against the Grain

April 1, 2021

Sour mash bourbon; it’s the way it’s always been done in Kentucky, and the way it shall forever be. Except, there’s now a cadre of Kentucky bourbon producers who are opting to make sweet mash bourbon. These producers are forgoing fermentation tradition in favor of a method they feel better suits their specific goals.

It’s worthwhile to think about why sour mash was first used and how it became standard protocol in bourbon production. The use of a sour mash has been widely credited to Dr. James C. Crow in the early 19th century — though that’s now seen as somewhat apocryphal. Indeed, it’s more likely that Crow fine-tuned and popularized the process with his scientific approach. In short, sour mashing is the process of adding a portion of a prior fermentation batch into the next run. It was done as a means to stave off bacterial growth while improving both the whiskey’s quality and consistency.

Sweet Mash Bourbon Advocates

With today’s greater technological capabilities and scientific understanding though, sour mash is no longer necessary to achieve those results. “Our sweet mash process lets us highlight many things, though it leaves you open to more contamination issues and losing batch to batch continuity so that forces us into higher standards with our cleaning and fermentations,” says Jerod Smith, project manager at Wilderness Trail Distillery. “Having to pay more attention is a good thing for us as it lets us always be doing our best possible job.”

Wilderness Trail is at the vanguard of Kentucky’s sweet mash bourbon revival and that’s thanks to how the distillery came to be founded. It’s actually an offshoot of Ferm Solutions, a company which designs and provides yeast strains and consults on all aspects of fermentation to a huge swath of the beverage alcohol industry. “These experiences on large scales led us to believe that the best way to get the flavor that we wanted from our own product was with sweet mash,” Smith says.

Cleanliness is Key

“Sweet mash requires us to pay extremely close attention to our cleanliness,” says Caleb Kilburn, master distiller at Kentucky Peerless Distilling. “While the soured effect in sour mashing intrinsically makes it resilient against contamination, a sweet mash is vulnerable in its early stages. This requires a lot of time and dedication to properly clean and sanitize our equipment. Through this level of attention to detail, we are able to safeguard the batches, ensuring our desired result.”

Along with Castle & Key Distillery, Peerless is one of two other mid-major, column still distillation Kentucky producers currently using sweet mash fermentation. It shouldn’t come as a surprise that both worked with Ferm Solutions in the development of their own protocols.

“The vast majority of distilleries produce great whiskey using a sour mash technique,” Kilburn says, noting that the ongoing use of sour mash is due to a variety of factors. This includes its historical success and maintaining existing flavor profiles. Furthermore, the specialized equipment and processes in many distilleries are designed to work within a sour mash environment. “By not being tethered to an existing flavor profile, newer distilleries are typically the ones charting the new territory that sweet mash represents.”

sweet mash bourbon


Easier for Multiple Mash Bills

Castle & Key opts to make sweet mash bourbon in part because of the breadth of the products the distillery produces, for itself as well as contract clients, with approximately 25 mash bills running per year. “These various mash bills also use one of six different yeast strains and can have variations in the mashing process, as well as the fermentation conditions, depending on the desired outcome,” says Jon Brown, Castle & Key quality manager.

“Since sour mash involves using the backset from a previous fermentation to adjust pH and provide nutrients for healthy yeast fermentation, it makes it challenging to keep consistency in the general make-up of our backset with constant product shift,” Brown continues. “For us, we are able to control batch variation and yeast management by using a sweet mash much more efficiently.” Though it should be noted that with multiple column stills to play with, Castle & Key is also planning on producing sour mash whiskey in the future.

Sour Mash Bourbon vs. Sweet Mash Bourbon

Is sour mash actually sour? Is sweet mash actually sweet? Yes and no.

Consider what fermentation does – yeast converts sugar into alcohol. And in the absence of those sugars, there’s a higher level of acids. At the same time, there’s a corresponding drop in pH. “Not using acidic backset allows for the distillate to be more neutral in pH and thus taste sweeter right off of the still and out of the barrels after aging,” Smith says. “It’s not actually sweeter with sugars, just less acidic so the natural grain flavors show.” He also notes that cleaner fermentations reduce unwanted fusel oils. This shaves time off maturation, or what he calls “barrel remediation” time.

Further, consider that there’s a growing number of distilleries that advocate for lower distillation and barrel entry proof. For Peerless, the capability to do so effectively starts with sweet mash. “Sweet mashing results in a cleaner, sweeter distiller’s beer,” Kilburn says. “The lack of the traditional ‘soured’ note allows us to be more aggressive in the distilling process, distilling at a much lower proof, [and] maximizing the fruit and floral characteristics of the distillate.” Sweet mash fermentation then should be seen as an intrinsic partner towards unlocking the benefits of low barrel entry proof.

Kentucky sweet mash bourbon is unusual, and that stands apart as a sellable point of contrast for consumers. But that only works if it’s done well and the whiskey hits the right notes.

“Making sweet mash whiskies is a differentiation for us as we believe it lets us reach our highest potential and make the best whiskey that Wilderness Trail can,” Smith says. “That is our competitive advantage because we make really dang good juice. It does set us apart in the marketplace but that wouldn’t matter if it wasn’t good whiskey.”

Ready to try some sweet mash bourbon?

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