Bourbon or rye? You can’t tell the difference, says study

By Scott Weybright, College of Agricultural, Human & Natural Resource Sciences
and Lauren Ingeno, Drexel University

RICHLAND, Wash. – Whiskey aficionados may claim that Manhattans must be made with fiery, grassy rye while an Old Fashioned requires the sweetness of bourbon.

But a new study from a Washington State University aroma and flavor chemist and colleagues shows the average consumer cannot distinguish between the two flavors.

Tom Collins, a WSU assistant professor in viticulture and enology, found that when asked to blindly sort American ryes and bourbons, participants were more likely to group together products by brand rather than type of whiskey.

The results were published in the Journal of Food Science with co-authors Jacob Lahne at Drexel University and Hildegarde Heymann at the University of California, Davis.

More flexibility for mixability

“There are differences between rye and bourbon,” Collins said. “But they aren’t nearly as different as we think they are. In a blind test, it’s really hard to tell a difference.”

Drexel’s Lahne, the lead author, agreed, saying people who work with bourbon may be able to experiment a little more.

“There is definitely a tendency for bartenders to talk about how some drinks should absolutely be made with bourbon or rye, and I think it’s clear now that there is more flexibility,” Lahne said. “In a way it’s fun and exciting – it gives you a bigger universe to play with.”

The only legal difference between bourbon and rye products is their mash bill, or grain content: Bourbon must be fermented from a mash that is a majority of corn, and rye from a majority of rye. Otherwise, the legal and stylistic requirements for the two products are identical.

So it’s possible for a 2 percent difference in mash bill to tip a whiskey from one category into the other.

Putting supposed difference to the test

Yet in both pop culture and whiskey educator circles, the two kinds are held to be distinct – bourbon is often described like smooth caramel while rye is called dry and brash.

Despite the quickly growing demand for whiskey in the United States (with revenues over $2.6 billion in 2014), there had been no rigorous examination of the assumed difference between bourbon and rye.

Collins and his colleagues wanted to know, how can straight rye and bourbon be so dramatically different if their basic recipe is so similar?

They presented 21 study participants with trays of 10 anonymized whiskeys – five bourbons and five ryes – in random order. The participants were instructed to smell but not taste the alcohol. This method is in accordance with published guidelines for Scotch whisky evaluation.

The participants were then asked to organize the whiskeys into no fewer than two and no more than nine groups, by any criteria they wished.

In a second session, when the participants came back days later, the same whiskeys were presented in an identical fashion with new, randomized labels. Participants were asked to sort the whiskeys into groups again.

The researchers next used a statistical analysis (called DISTATIS) to interpret the responses.

Whiskey age, brand more telling than type

Collins and the team found that the subjects did not separate the whiskeys based on mash bill (bourbon vs. rye), but instead were more influenced by properties like alcohol content, age at bottling and brand. For instance, participants were very likely to group together Jim Beam whiskeys.

Collins said this is likely because individual distillers make their bourbons and ryes in similar ways and use similar barrels.

“So much of the characteristics of any whiskey come from the barrels,” he said. “And when you use the same barrels for each style, there will naturally be strong flavor similarities.”

The perceived differences between bourbon and rye may stem from a time in history when mash bill differences were greater, he said. However, modern American whiskeys that are most popular today are more closely related.

In future studies, Collins and his colleagues plan to further explore how specific sensory attributes match up with chemical analyses of each whiskey.

Contact:
Tom Collins, WSU viticulture and enology, 509-372-7515, tom.collins@wsu.edu