Which Type of Corn Makes the Best Whiskey?
Look out over several acres of corn grown on John Sawyer’s farm and you probably wouldn't notice anything out of the ordinary—vibrant green stalks growing in tidy rows set against a backdrop of the Central Texas sky.
But something different is going on deep inside these plants, on a genetic level. Something that, when turned into whiskey, creates a distinctive flavor.
“It looks the same as commercial corn but, genetically, it’s very different,” said Rob Arnold, the 32-year-old head distiller at Firestone & Robertson, the Fort Worth craft distillery that uses Sawyer’s corn and other grains to make whiskey. “The stuff we care about is locked inside.”
Whiskey is primarily made with yellow dent field corn (typically yellow dent No. 1 or No. 2, the U.S. Department of Agriculture’s quality grade), grown commercially in huge quantities to feed cattle and make ethanol and plastic products. But distillers like Arnold are starting to ask the question: wouldn’t it be better to use corn grown specifically for whiskey?
Arnold is in a unique position to find out. In addition to making whiskey full-time, he’s also studying plant breeding and genetics as a doctoral student at Texas A&M University.
Working alongside university researchers, Arnold is studying hybrid corn varieties to understand how their genetic makeup, when coupled with environmental factors, can affect the taste of whiskey.
“I realized there was this massive dichotomy between how winemakers pursue grape selection and how whiskey-makers pursue grain selection,” Arnold said. “If you were to go ask any distiller, ‘What kind of grain do you work with?’ a bourbon distiller is going to say, ‘Well, we use yellow dent corn.’ That’s about as shallow or surface-level as a winemaker saying, ‘Well, I use red grapes to make wine.’”
It’s not that commercially grown, yellow dent corn is bad, per se. But it’s not being grown with flavor—or whiskey—in mind.
“Because distillers primarily buy grain from the commodity market, we’re working with varieties bred and selected to feed chickens and cows or to make ethanol and, primarily, what they were selected for was yield—how many bushels per acre can we grow?” Arnold said. “That’s not a bad thing. But a lot of the science has shown that when you breed for yield, you inadvertently dilute flavor. We lose some of the nuances when we’re trying to grow for yield.”
Arnold is quick to note that commodity grains can, and do, make amazing spirits. But distillers may be missing out on more diverse flavors by only using grains grown for other, less appetizing purposes.
Grains are one of the many elements that go into making great whiskey. But unlike the weather or barrel-to-barrel variation, grains are one factor distillers can control, if they’re willing to spend a little time and money.
“How you pursue flavor in whiskey is a quilt that’s stitched together, and anytime you pull one of those threads, the entire design shifts,” Arnold said. “Every one has a chance to shift the quilt a little bit. It doesn’t mean you’re going to create an entirely new whiskey. It constantly allows us to shift and evolve our flavor to dial in quality, to dial in diversity. It’s one part of the flavor puzzle.”
Firestone & Robertson isn’t the only distillery focusing on grains. A similar project is underway in Washington, where distillers at Westland Distillery and researchers at Washington State University are studying and developing barley varietals. Researchers at Oregon State University are also taking a closer look at barley for beer, spirits and other food products.
And in South Carolina, High Wire Distilling Co. is using a dark red, historic moonshine corn varietal called Jimmy Red that researchers and farmers brought back from the brink of extinction.
“You’ll rarely, rarely hear any bourbon distiller talk about their raw materials—the whole thing starts at the barrel,” said Ann Marshall, who co-founded High Wire with her husband Scott Blackwell. “We just felt like there was a huge piece of the puzzle missing and that was that raw ingredient of corn.”
At Firestone & Robertson, the quest to find a corn better suited to whiskey started with yeast.
Arnold, who grew up in Louisville, Kentucky, initially came to Texas to earn a PhD in biochemistry at the University of Texas Southwestern Medical Center in Dallas (he was studying marine natural products, compounds that can be used as antibiotics or other drugs).
But bourbon is in his blood—his uncle, grandfather, great-grandfather and great-uncles all worked in the industry—and Arnold soon began talking to local developers about opening a distillery.
He eventually connected with Leonard Firestone and Troy Robertson, who were in the early stages of launching their own distillery.
Arnold earned a master’s degree, but ultimately left the biochemistry program to pursue distilling full-time. He became Firestone & Robertson’s first employee: head distiller.
But Arnold is really a scientist in distiller’s clothing. His first task at the burgeoning company was to find and isolate a strain of yeast native to Texas. Without any prior yeast experience, Arnold simply used his scientific background and training to figure it out, performing DNA analyses and microbial isolations on more than 100 wild yeast samples found throughout North Texas. (Fittingly, the proprietary strain the distillery now uses came from a pecan nut on a ranch southwest of Fort Worth—pecan is the Texas state tree.)
That yeast process got Arnold thinking about all the other ingredients that go into whiskey. At the time, the distillery was using grains grown only in Texas, but was sourcing them from a large grain elevator, which meant they didn’t know where the grains were grown or what varieties they were using.
Around the same time, Firestone & Robertson began partnering with farmer John Sawyer, who now grows all of the grain that goes into the company’s spirits. With that relationship in place, Arnold began a doctoral program at Texas A&M under Seth Murray, a professor in the soil and crop sciences department specializing in plant breeding and genetics.
Murray had also separately wondered why distillers didn’t care more about grains. Several years earlier, he’d approached local distillers about using corn varieties he developed, but ultimately couldn’t find anyone who was interested.
Then, Arnold came along. An email went around Murray’s department.
“‘There’s this weird distiller guy who wants to do a PhD,’” Murray said. “All the rest of the plant breeders were like, ‘Well, that’s not what plant breeding is for,’ and I was like, ‘Yes, please.’”
Arnold began by studying 10 to 15 hybrid corn varieties that Murray was most excited about—they had high yields, but were also genetically distinct from one another, which could lead to different flavor profiles. These tropical hybrids had a genetic makeup closer to heirlooms grown in Mexico, Central America and South America than to the modern yellow dent corn bred for the Corn Belt.
After distilling and tasting those varieties, Arnold narrowed the pool down to three. After conducting some initial trials at A&M, the distillery planted five acres of the corn varieties on Sawyer’s farm last summer.
Whiskey made from those crops is currently aging, but even the white dog had a distinct flavor.
“Our A&M corn made a sweet and fruity type of whiskey, whereas the commercial corn was more cardboardy and bready and leathery,” said Murray.
This summer, they plan to grow 25 to 30 acres of the three corn varieties on Sawyer’s farm and hope to increase production to thousands of acres in the years to come. The distillery may eventually narrow it down to one proprietary corn strain, though using just one variety carries some risk — the entire crop could be taken down by a pest or disease, Arnold said.
So, why hasn’t anyone developed corn for whiskey before now? The commodity grain system is reliable, efficient, cheap and easy: it’s a proven system that works. Public plant breeders, those who work independently from massive, for-profit corporations, are becoming exceedingly rare. Plus, not all distillers are convinced that grain matters that much, or that terroir exists in whiskey at all.
“Distillers had it in their minds that the still matters, the water source matters, the oak barrel matters, the aging process matters, but that the corn is just—who cares? Corn doesn’t impart any flavors,” said Murray. “It was just a starch you could ferment and then distill.”
Arnold, for one, is a firm believer in terroir, which he characterizes as the interaction between a plant’s genes and its environment. He and fellow Texas A&M graduate student Ale Ochoa (who is now Firestone & Robertson’s whiskey scientist and blender) found measurable chemical differences in different varieties of corn grown in four parts of Texas, each with unique climate and soil conditions. The results of that study were published in the peer-reviewed scientific journal Plos One last August.
Arnold, who’s now working on a book about the terroir of whiskey, also points out that selecting grains for flavor is not a new concept. Before Prohibition, distillers sourced grains from nearby farmers, who grew crops primarily to feed their families. They cared about flavor then — and maybe we should, too.
“Back then, grain was for food. Flavor was always part of the story,” Arnold said.