This is Your Beer on Wood

Some call it winter, others call it thicc boi season. The air cools, night lengthens, and every fiber of your beer drinking being clamors for the sweet, roasty goodness of a Barrel Aged Stout. While we’ve played around with barrels since our earliest days of operation, our Barrel Aging program is more active than ever this year, with some fancy new packaging, a slew of first-time bottle releases, and a partnership with the cross-river whiskey wizards at New Riff. With that in mind, we wanted to take some time to dive into the world of beer and wood, looking at everything from the biochemical processes behind our favorite oak-assisted flavors to the trial-and-error ethos that’s birthed some of our most cherished beers. Be warned, this one’s for the nerds.

4 bottles of Rhinegeist Barrel Aged Ink variants sitting atop a barrel

Peeling Back the Wooden Curtain

For all the advancements in fermentation science, brewing technology, and knowledge transfer between brewers, brewing still holds an alchemic air of mystery. Fermentation can be equal parts art and science (they call it craft beer for a reason), and nowhere is this intersection of education, history, and magic better displayed than barrel aging. From wild culture and mixed fermentation ales to the most toothsome, adjunct-heavy Imperial Stout, beer and wood boast a well-spring of liquid potential. 

It’s important to note that wood and beer go way back. Keeping beer in steel tanks is a relatively new phenomenon, a practice made possible within the last century. Prior to that, all beer was kept in wood. Many of today’s methods, informed by both scientific advancements and careful study of brewing technique, have been practiced for centuries, with two key differences. First, while beer makers traditionally aimed to minimize the influence of wood on the final flavor of the liquid, today’s brewers work in the opposite direction, leaning in to the influence of oak on the finished product. Second, brewers of centuries past lacked the biochemical explanations behind why their methods worked so well.

One such explanation, yeast, was completely unknown to a brewer in, say, the mid sixteenth century. Brewers would stir wort with a wooden paddle, passing their paddles down from generation to generation. Unbeknownst to them, yeast lived in the pores of the wood, and each time they stirred they were inoculating the wort. Scientific understanding or not, those brewers knew how to get the product they wanted. 

A similar example is seen in their selection of barrels for souring. Old brewers didn’t know why certain barrels made better sour beer, because they didn’t know that microbes were living in them. But they would, without knowing it, select the barrels that had the right cultures in them. This was the main reason brewers started using foeders, because they could get the vessel to have what they wanted in it and keep putting liquid in it without altering the container at all. The bugs lived in the wood and would sour the beer without the brewers needing to do anything else. 

Rhinegeist Oak Foeder

An oak foeder, where beer is inoculated with our house cultures

An old German drawing showing brewers from the seventeenth century

Stamp issued in 1983 celebrating the 450th anniversary of the Reinheitsgebot, the German Beer Purity Law

So, What Do We Know Now?

To start, barrels have an ideal surface for yeast. Wood is porous with varied texture, and the barrel shape allows a small amount of liquid to interact with a large surface area. The interactions between beer and wood occur slowly over a relatively large distance, letting the liquid carefully mature over the course of months or years. Leaving adjuncts aside (e.g. coffee and cacao beans infused in a Stout), the nuanced interactions between just beer and wood impart inumerable complexities to a brew. 

One such interaction is the lignin to vanillin transformation. Lignin is an organic polymer that exists in a host of plants, including oak trees. Coincidentally, lignin is just vanillin with an extra end of a molecule attached (vanillin is the compound responsible for the flavor of vanilla). Yeast will rip off that end piece of lignin and turn the protein directly into vanillin. In Barrel Aged Stouts, for example, this is where most of the marshmallowy sweetness comes from. This is why so many wood mellowed Stouts will reference vanilla in their tasting notes, even when there are no additions of vanilla bean.

Lactones also play a key role, lending an oily, coconutty sweetness. Naturally occuring in oak, these lactones will be absorbed into the liquid, lending added sweetness beyond the vanilla-marshmallow profile. American Oak actually has twice as many lactones as French Oak, and each type of wood will be selected to achieve different flavor profiles. French Oak is used to accentuate vanilla without dialing up the overall sweetness too much, whereas American Oak, used for Bourbon, ramps up that extreme sweetness.

Last but not least, tannins act as a critical antioxidant and flavor component. Tannins are found in many foods and beverages, notably coffee and tea, lending astringency. (Next time you steep English breakfast tea, let the bag sit in for several minutes more than recommended to get a feel for this.) In barrels, tannins are leached out quickly and are then destroyed by oxygen. Once oxidized, these tannins will then protect the rest of the sugars in the malt from oxidizing (hence their title of “antioxidant”).

This process is a balancing act, because you want some oxygenation without full oxidation of the liquid. Thankfully, barrels have tiny pores, allowing in only small amounts of oxygen. Left in the barrel for the right amount of time, beer can pick up delicious touches of Sherry, licorice and red fruit. Keeping the beer in for too long, though, will result in gross, papery off flavors. 

Wine is a helpful analogue for this phenomenon. Wine, especially Red Wine, which is more tannic, is typically aired out before consumption (“letting it breathe”). After an hour or so, the wine will open up, expressing a fuller range of flavor. If you were to wait for a few days, however, the wine would fully oxidize, leaving stale flavors ranging from nuts to burnt fruit to wet paper. 

Brewer purging barrel at rhinegeist brewery

Body and Soul (and Amino Acids)

Today’s barrel aged offerings run the gamut from beefy Imperial Stouts to delicate Smoked Pilsners, but there are some general characteristics amongst barrel-ready beers. 

“A complex malt bill is important,” says Travis, our in-house Sensory Specialist. “That will give some interesting sugars and proteins to interact with the wood.”

In general, dark malts fare better. As Travis explains, “lighter malts don’t micro-oxidize well because they don’t have as many of those interesting proteins and bigger sugars. In general, the bigger, thicker and darker a beer is, the better it will age in a barrel. And it’s similar with wine. You don’t want to overage a Chardonnay, for example. Those wines don’t sit in wood nearly as long as their darker counterparts.”

Speaking on the importance of a full body for wood-mellowed liquid, Travis adds that the majority of heavy proteins will break down in the barrel, leaving you with a much thinner beer. 

“Proteins are large, shape dependant molecules, and when it leaves its proper environment the shape will morph and the protein will denature. Eventually it will fall apart into amino acids, leaving the liquid without those big, thick molecules that impart a full body.”

Even when aging big beers (like our Imperial Stout Ink, for example), we keep some non-wood aged beer on hand to blend when the rest of the liquid leaves the barrel. This prevents an overly thin profile. 

Samples of Ink sitting atop barrels, showing how Rhinegeist tests liquid

Samples of Barrel Aged Ink pulled from their barrels

Bottle and glass of Rhinegeist barrel aged Mushhushshu atop barrels

Mushhushshu, our Dark Ale Blend with Coffee, Chocolate & Vanilla, aged for 10 months in New Riff Bourbon barrels

Fresh Wood

Sourcing used spirit barrels to house a beer can be a finicky process, often demanding brewers drive hours away to a third-party supplier to take home weeks-old barrels with waning glimpses of the liquid it once housed. We’re fortunate to brew in Cincinnati, a historical nexus of beer and bourbon production. Better still, our recent partnership with New Riff has given us access to barrels that were dumped mere hours ago. 

Fresh, wet barrels are an invaluable asset to any barrel aging program. First, if the barrel is still wet with liquor, it’s guaranteed to be clean; nothing can live in that environment. Equally important, a wet barrel means it won’t leak. The proteins and tannins haven’t been fully stripped either, allowing much more of the barrel character to shine through in the finished beer. This stripping is actually the reason Scotch is aged in used barrels, whereas Bourbon is aged in fresh barrels. In Scotch, they don’t want the liquid to pick up nearly as much flavor from the wood, they want the peat to shine through without the vanilla sweetness of Bourbon. 

Barrels at New Riff's rickhouse

Barrels at New Riff’s rickhouse in Newport, KY

Fail Again. Fail Better. 

Earlier, we referenced the dual nature of brewing as both an art and a science. In our own barrel aging program, much of what we’ve learned has simply come from experimentation. Failing, iterating, trying and retrying has taught us what flavors we like and how we can best achieve those profiles. 

“That’s the biggest thing,” says Travis. “Just trial and error––figuring out how long each beer should live in the barrel and taking the beer out of the barrel at the right time is, I think, what we’ve gotten way better at recently.”

The beer needs to have gained enough flavor but not have gone beyond the point of actually starting to oxidize, as we discussed earlier. 

This trial and error approach has developed some of our most exciting and hard-to-produce beers, from Sherry Barrel Aged Ink, our first beer to ever medal at Great American Beer Festival, to Double Oaked Mastodon. A Belgian Dark Ale aged for a year in bourbon barrels, then for six more months in red wine barrels, Double Oaked Mastodon is one of our strongest (and most awarded) beers. 

As Travis explains, “the aging process we landed on wasn’t the ‘smartest’ way to make that beer. But the way our team makes it is the only way to get that flavor, because if we just aged half the beer in bourbon barrels and the other half in red wine barrels and blended them, the beer would not benefit from the progression of all the compounds breaking down before picking up the wine character at the end. The final beer would not be nearly as complex.”

Rhinegeist Barrel Master Luke holding Double Oaked Mastodon bottles

Barrel Master Luke with some Double Oaked Mastodon

Showing the process of filling barrels with beer at Rhinegeist brewery

Wood is Good.

Barrel aging beer can be expensive and time consuming, but we hope that we have driven home how worthwhile it can also be. While it may not be the right choice for every style, there really isn’t anything like a beer that has seen some time on wood in terms of subtle nuance and depth of character. Next time you’re slowly sipping your favorite barrel aged brew and contemplating the mysteries of maturity and mortality, take a minute to think about how the beer in your glass may have undergone a life-cycle of birth and maturation similar to your own, and remember these life-affirming lyrics from “The Beer Barrel Polka” as popularized by the Andrews Sisters:

There’s a garden, what a garden

Only happy faces bloom there

And there’s never any room there

For a worry or a gloom there

Oh there’s music and there’s dancing

And a lot of sweet romancing

When they play the polka

They all get in the swing

Every time they hear that oom-pa-pa

Everybody feels so tra-la-la

They want to throw their cares away

They all go lah-de-ah-de-ay

Then they hear a rumble on the floor, the floor

It’s the big surprise they’re waiting for

And all the couples form a ring

For miles around you’ll hear them sing…

Roll out the barrel, we’ll have a barrel of fun

Roll out the barrel, we’ve got the blues on the run

Zing boom tararrel, sing out a song of good cheer

Now’s the time to roll the barrel, for the gang’s all here

Da-da-da-da, da-da-da-da,…