Correction: An earlier version of this column misspelled the first name of Harlen Wheatley, the master distiller at Buffalo Trace Distillery. This version has been corrected.

Here’s something you’ve probably never considered: Does bourbon taste better when it’s aged in barrels made of wood from the top of a white oak tree, or does it taste better in barrels made from the bottom of the tree?

That’s the sort of issue you start pondering when you spend a couple of days hanging out with whiskey geeks. Which is precisely what I did last week in Frankfort, Ky., where Buffalo Trace Distillery unveiled a batch of bourbons that were the result of its super-secret, two-decade-long Project Holy Grail, which I wrote about in March.

Like a boozy Lancelot, I must first report that I returned home from my pre-Derby trip to Kentucky bourbon country without exactly having tasted the Holy Grail. As Mark Brown, president of Sazerac Co., which owns Buffalo Trace, told the assembled journalists and critics: “Have we found the Holy Grail? No. Have we found clues? Maybe.”

Those clues were revealed in the form of the limited-edition Single Oak Project , a collection of 90-proof bourbons that will sell for $46 per 375-ml bottle. Fewer than 400 bottles of each will be released, and 12 new bottlings will be released every quarter for the next four years. (To find some near you, call the distributor, Republic National, at 202-388-8400.)

Now, plenty of distilleries release expensive, limited-edition bottlings. But the Single Oak Project is unique and more noteworthy, for several reasons.

More than a decade ago, Buffalo Trace went into the Missouri Ozarks to hand-select 96 trees. Those trees were split in half, then made into staves for 192 barrels, each tweaked according to numerous variables. Half of the barrels were air-dried for six months and half for 12 months. Some of the barrels were charred very dark, and some were charred lighter. Some barrels were filled with wheat-recipe bourbon, others were filled with rye-recipe bourbon; some of the contents was 105-proof, some was 125-proof.

We can now see the resulting products, each aged eight years and labeled by barrel number. If the first batch is any clue, they are exquisite, with at least two of them, Barrel 131 and Barrel 68, among the finest bourbons I’ve ever tasted. As for whether the top or bottom of the tree makes a better bourbon: Barrel 131 was made from a top half and 68 from a bottom, so other factors, such as recipe and wood-grain size, are also in play.

“We’re very serious about this,” said Harlen Wheatley, Buffalo Trace’s master distiller. “We want to know whether a barrel is made from the top half or the bottom half of the tree. It makes a big difference.”

Go ahead and roll your eyes if you must. But let me say here very clearly: It’s totally true. There are a lot of romantic, and exaggerated, tales in the spirits business. This is not one of them.

After tasting the first dozen bourbons in the Single Oak Project, I was amazed by how much difference a single variable, such as wood-grain size or tree portion, makes. I tasted two bourbons, side by side, that had been distilled with the same recipe, put in the same proof and at the same time, and stored in similar warehouse locations. The bourbon that was stored in the barrel made from the top half of the tree had significantly different characteristics (fruitier, crisper, lighter) from the one from the bottom half of the tree (richer, more caramel notes, deeper color). In fact, once you’ve bought the whiskey and tasted it, you can log on to and, after registering and rating, find out exactly which variables your barrel number possesses.

Still, comprehensive as it is, the Single Oak Project doesn’t bring us to a Holy Grail. “You would need five quadrillion barrels to fully investigate all the variables,” said Sazerac’s Brown. For instance, Buffalo Trace has thus far isolated only 125 of the 300 possible chemical compounds in bourbon.

“We looked at and dissected the ratings of top whiskey writers,” Brown told us. Then, in the tasting lab, the distillers investigated which chemical compounds caused certain flavors and aromas to occur. For instance, when a critic described a bourbon as “fruity” or “banana,” Buffalo Trace could tell that what he’d detected was most likely the presence of the chemical compound amyl acetate in whiskey.

“So have you used that knowledge to fact-check your critics?” I asked. “Have you determined that certain aromas they describe can’t possibly be in a certain bourbon because the chemical compound doesn’t exist in it?”

“No, no,” said Brown, looking around at the writers in the room and chuckling nervously. “We trust the critics implicitly.” There were other chuckles in the room as well that might or might not have been nervous.

Not all the compounds result in positive flavors and aromas. Brown shared with us a list of descriptors that Buffalo Trace tries to avoid in its whiskeymaking. “In no highly rated bourbon did the words ‘puke,’ ‘tar,’ ‘jasmine’ or ‘balsamic’ turn up in the review,” he said. Other descriptors they seek to avoid: blue cheese, popcorn, pumpkin, peanuts, celery and roses.

I found the last of those — “roses” — interesting and a little confounding. Earlier in the day, I’d visited the nearby Four Roses distillery in Lawrenceburg. While there, I tasted the company’s delicious new limited-edition single-barrel bourbon. Everyone in the Four Roses tasting room, including me, was excited about the unique floral aroma that this bourbon exhibits — and that some people would describe as having a hint of . . . freshly cut roses.

Which might prove that no matter how much science you throw at a project like this, a whiskey assessment will always come down to a subjective preference in the nose and mouth of the drinker.

“This project actually raises more questions than it answers,” said Drew Mayville, Buffalo Trace’s master blender. “This is why we embarked on this project: to dispel myths, to learn new things.

“Who knows if we’ll ever reach the Holy Grail? Or who knows; we just might get lucky one of these days.”

Wilson is the author of “Boozehound: On the Trail of the Rare, the Obscure, and the Overrated in Spirits” (Ten Speed Press, 2010). He can be reached at Follow him at