Bourbon vs. Rye: Science Says Everything You Know Is Wrong

Can you really taste the difference between bourbon and rye, or just think you can?

Dr. Jacob Lahne (pronounced “lahn”) is a whiskey drinker and flavor scientist. Last January, he and three co-authors published a paper claiming even well-trained tasters can’t reliably distinguish between bourbon and rye whiskey. It was very much a shot across the bow of American whiskey’s conventional wisdom that sprouted some debate in professional distillers’ online groups. Lahne liked that because, as a professor, he says he’s always looking for things that are “attention grabbing”.

In previous research on American and Scotch whiskey, Lahne and his collaborators had noted that the chemical lines between rye and bourbon were indistinct. They designed a new study to determine whether rye and bourbon could be distinguished by taste. They trained 11 “judges”, most of whom came out of the exceptional wine program at University of California at Davis. The judges had no idea what it was they were testing. In guided, blind tastings, they identified 23 flavor elements in American whiskey and developed a uniform vocabulary to describe them.

Then, the judges tasted 24 whiskeys, always blind and in different orders and combinations, assembling thousands of tasting notes using the agreed-upon descriptors. And what those impressions added up to was, basically, nothing. Lahne published the results in the Journal of Food Science with a title only an academic could love: “Bourbon and Rye Whiskies are Legally Distinct but Are Not Discriminated by Sensory Descriptive Analysis”.

“As someone who buys and drinks a lot of whiskey,” says Lahne from his office at Virginia Tech University, “I personally thought the difference [between rye and bourbon] wasn’t large. It was nice to see my suspicion confirmed.”

Dr. Jacob Lahne, courtesy Virginia Tech University

What the experts say

Lew Bryson, the author of Whiskey Master Class and Tasting Whiskey, is quoted in the study as an example of the conventional wisdom that bourbon and rye are discernibly different. Bryson lives in Pennsylvania and has, it’s fair to say, a fondness for the state’s native spirit. He had no idea his writing had been quoted in the study and received the news with good-natured disbelief.

“I was going to say that’s nonsense,” he says, “but I won’t go that strong. There are a lot of different factors and I don’t think it could be simply evaluated.”

Other whiskey partisans had similar reactions.

“I would obviously dispute that,” says Herman Mihalich, founder and distiller of Dad’s Hat Rye. “When people taste our whiskey, they do see a very stark difference from bourbon.”

And, finally, Colin Blake, who teaches distilling at the Distilled Spirits Epicenter in Louisville, rejected the premise with a barrel-strength sound bite aimed at one of Lahne’s collaborators, whose name is—no kidding—Tom Collins: “I don’t trust whiskey information from a guy named after a gin drink.” Never mind a gin drink that is said to be born out of an elaborate practical joke.

Understandable, certainly. But even if you reject Dr. Lahne’s contention that bourbon and rye are indistinguishable, there is a lesson hidden in the study.

the judges at Virginia Tech

The science behind the flavor

Lahne’s selection of what he calls “commercial” whiskies used in the study contain just one with no corn (Bulleit Rye) and one with no rye (Maker’s Mark). The rest were blends of both corn and rye, inevitably exhibiting attributes of both. As noted by Dr. Lahne, “it is possible for a 2% difference in mashbill to tip a whiskey from one category into the other”, and it is not possible for even the most discerning tasters to consistently recognize such a small difference.

“You can’t tell the difference,” says Bryson, “because there’s a hell of a lot of rye in your bourbon.”

“The chemistry of rye is different from the chemistry of corn or wheat or malt,” says Nicole Austin, General Manager and Distiller at George Dickel. “What doesn’t follow is that is going to be expressed in the final product in a way that is strong enough that you’re going to pick it up. Mashbill is only one of 10 or 20 decisions that relate to the final flavor.”

Novelty sells

The major whiskey brands’ expressions of rye often have more to do with marketing than aesthetics. “Marketers in spirits talk a lot about the Millennial consumer,” says Marianne Eaves, the former master distiller at Castle & Key who now runs a thriving consulting practice. “Millennials like trying new things, tasting new things, want to feel special and unique and thoughtful. You want to have the versatility in products for them to explore and discover.”

“When Woodford came out with their rye whiskey,” says Mihalich, “they on-purpose didn’t make it much different from their bourbon, because they were trying to attract bourbon drinkers to rye.”

Because… science?

Adding to the confusion is the chemistry of rye, which contains many of the same cellulose compounds as the oak used to age whiskey.

“There’s no hard demarcation between the rye contribution and the barrel contribution,” says Connor O’Driscoll, master distiller at Heaven Hill. “Complex cellulosic compounds (in both rye and oak) break down and produce the flavor compounds that make up spice notes, cinnamon, pepper, clove…”

Clay Smith, the distiller at Moonshine University in Louisville, read Lahne’s study and suggested it might be more illuminating if it had controlled for the impact of the barrel.

“If you’re going to make the statement that rye and bourbon aren’t different,” he says, “you would have to eliminate that variable and just use a clean distillate.”

Dr. Lahne leads the tasting at Virginia Tech

Which is something that occurred to Lahne and his collaborators, too. When they got done with their study proving that bourbon and rye are no different, they put together another study (“Mashbill and Barrel Aging Effects on the Sensory and Chemometric Profiles of American Whiskey”) that seemed designed to disprove what they’d just asserted. They custom-distilled whiskey to specific, graded mashbills ranging from all-the-way-rye to all-the-way-corn, and then went through the whole cycle of vocabulary development and repetitive blind tastings again.

“At extreme mashbills,” he says, sounding remarkably cheerful about undermining his own research, “we did find a difference.”

(In the conclusion to the new report, Lahne and his co-authors seem to have picked their next fight, saying they’d proved “that storage conditions throughout the study did not alter whiskey characteristics.” Which will, of course, come as news to the hundreds of people who are employed moving barrels around rickhouses to maintain the consistency of aging whiskey.)

Colleen Thomas, Director of Member and Public Affairs at the Kentucky Distillers’ Association, kind of shrugs off the whole discussion. Tasting whiskey is an individual, subjective experience, she says. How something tastes is in large measure based on the experience of the taster.

“There are only so many variables (distillers) can control,” she says, “and we keep drilling down to a tight little window. But at the end of the day there is a type of magic to it. That’s the appeal of whiskey, whether people can articulate it that way or not.”