How to Homebrew Barrel-Aged Sour Beer, According to Master Blenders

We’re entering the dead of winter. It’s too cold to be outside, let alone sipping a homebrewed hefeweizen out on the porch or gathering with friends at a biergarten. What better time for a funky experiment?

Barrel aging can be intimidating for homebrewers, not just because of the space required (where can you store a 60-gallon barrel anyway?), or the amount of base beer required (again 60 gallons is at least 10 standard homebrew batches), but because of the time required. A barrel aging experiment started now won’t be ready to sip on by the time the summer sun is out; it probably won’t even be quite right next winter; likely you’re looking at a 16-to-18-month aging period.

So, if you’re up for the challenge, we phoned two experts with advice to make that 18 months worth your time. Jim Crooks, the master blender at Firestone Walker’s Barrelworks, and Lauren Woods Limbach, the wood cellar director and blender at New Belgium, have all the info you need to get started on your first barrel-aged beer.

Choosing a Base Beer

The beginning of your path to barrel-aged sour looks like any other brew day. You’ll need to brew enough base beer to fill a barrel. For a homebrew club, each member can pitch in five to 10 gallons of the same style. For brewers going at it alone, it’s a good idea to look into sourcing a smaller barrel that will still require multiple batches to fill.

As far as what style to brew, both Crooks and Limbach agree a neutral base style is an ideal starter option.

“Always use lagers. Lagers have sulfites so they have natural antioxidants,” says Limbach. “It’s such an easy cheat to help control oxidation. I think they make better sours; the ester profile going in is so low.”

Starting out with low ester levels will prevent unexpected reactions during secondary fermentation and will help the brettanomyces or bacteria fermentation characteristics be more defined and specific. Many of Limbach’s sours at New Belgium start with a simple lager made from pilsner malt, limited hops, and a clean lager yeast.

“Start with something that’s mild, just neutral. Put that in the barrel with a highly expressive brett strain and see what happens, see if you like that,” says Crooks.

After confirming the brett strain is creating flavors you’re interested in, then you can try a farmhouse or Belgian base style and see how that changes the brett character.

Make sure to monitor the fermentation of your base beer closely because you’ll want to fill the barrel with beer that is between 60 and 70 percent attenuated, according to Crooks. “It’s a good intuitive way to make sure that your brett or lactobacillus fermentation is going to start up and go right away,” he says.

Both Limbach and Crooks remove primary fermentation yeast before adding beer to the barrels. This yeast can break down and cause off flavors during aging.

Inoculating

Once your base is ready to be transferred into the barrel, do everything possible to avoid contact with oxygen. Since the barrel- aging process takes a long time, even minor oxygen pick-up will cause major oxidation flavors in six to 18 months.

“You have to get the air out of your barrel. You have to. Get a carbon dioxide (CO2) canister and purge [the barrel],” Limbach says.

With the barrel filled, it’s time to add a culture of bacteria, brettanomyces (“brett”), or a mixture of the two (mixed fermentation). According to Crooks, “[The culture] should represent 10 percent of your beer. So, if you’re filling a five-gallon barrel, then half a gallon of that should be your brett or lacto culture.”

A common practice homebrewers use for sourcing bacteria and brett is collecting the dregs (the yeast and sediment at the bottom of the bottle) from their favorite commercial sour beers. These brewers are likely not getting the pure culture they’re hoping for because of interference from bottle-conditioning yeast or filtering of the commercial beer. In the case of Firestone Walker Barrelworks beers, most of the dregs are Champagne yeast.

Get a fresh and lively culture from yeast companies like WhiteLabs, Wyeast, or Omega online or at your local homebrew shop for best results.

Monitoring Aging

When the secondary fermentation is starting to slow, it’s important to observe the activity closely. The moment that brett is no longer active, all the oxygen-scavenging benefits of the fermentation are gone.

“If there is the presence of oxygen, you move into an aerobic fermentation. So acetobacter is happy,” Limbach says. “If you don’t get [the beer] out of the barrel you will start getting acetic acid (vinegar) pretty fast. Once you taste vinegar it’s just over. People try to blend it out but the problem is, it’s in there and it (active acetobacter) will take over again. So you can blend the vinegar flavor all the way out to where you don’t taste it, but that is just ruining more beer.”

Smelling Rotten Eggs? That’s O.K.

Vinegar might be a sign it’s time to dump a barrel but sulfur flavors and aromas like egg or burnt rubber are not a sign of trouble. “Sulfur itself is, to me, a note of a healthy brett fermentation in the early stages,” says Crook. “Like six months into a brett fermentation, I’ll walk by a barrel and it just smells like rotten eggs. I used to think, ‘Oh, no!’ But now, I go, ‘Oh, good.’ That’s a great sign that things are going well and will clean up into beautiful, beautiful aromatics.”

If sulfur aromas are coming from your barrel, just wait it out. If you do anything, top up the barrel with a fresh brett or bacteria culture to keep things moving. Even if there isn’t a sign of off flavors, the barrel should be topped up every six to nine months with fresh beer that’s actively fermenting with the culture in your barrel. This will help control oxidation in the barrel’s headspace and keep the fermentation active.

Between 1.5 and 2 degrees Plato (1.006 to 1.008 specific gravity) is considered terminal gravity for mixed-fermentation beer, meaning your brew is (finally!) ready for bottles.

Finishing it Off

When it’s time to rack the beer, be careful not to oxygenate it, Limbach warns. “Usually what happens is, everything with the fermentation was great,” she says. “Then, you go to rack the beer and you get all that oxygen back in it. When you’re packaging, be careful with that headspace. You have to purge [bottles] with CO2. Bottle conditioning doesn’t matter; the spontaneous oxidation from headspace happens so fast.”

At Firestone Walker Barrelworks, Crooks says, beers are dosed with about half a degree Plato of dextrose and are then bottle conditioned with DV10 wine yeast. The bottle conditioning process takes about six weeks. “There is a degree of bottle shock with the referementation,” he says. If bottles have a whiff of diacetyl when they are opened, the bottle conditioning process isn’t complete yet.

At every step of the racking and bottling process, move slowly, use CO2 to purge, and avoid splashing at all costs. Doing this will keep all the flavors of the beer bright and will avoid papery oxidative flavors.

The most important step in preserving a barrel is ensuring it is never dry. Luckily, what keeps it wet doesn’t matter too much. “You can always fill a barrel with de-aerated water, or water with some potassium metabisulfite and some citric acid to lower the pH,” says Limbach. “You can just refresh that solution every three months or so and you have an awesome storage solution.”

No Barrel? No Problem!

After documenting this process, it’s clear having a barrel at home just won’t be practical for many homebrewers. Both Crooks and Limbach agree that it’s possible to make excellent beer with wood chips and spirals.

“You’ll get better [wood] flavor from those things than you probably will a barrel; it’s surface area insanity,” says Limbach. If big marshmallow and vanillin flavors are the goal, she “absolutely loves” using oak spirals to achieve that profile.

Because of that surface area, Crooks suggests conducting a small test before adding the barrel alternatives to a carboy or fermenter. “The biggest pitfall is that you end up adding too much [wood] because it looks like such a little amount,” he says, “and all of a sudden you have this over-oaked beer that you’ll have to blend off.”

Measure a specific amount of beer or wort, add a standard amount of wood chips or spirals, and let it stand at the same temperature the larger batch is stored at for a few days. Taste the results and if the outcome is positive, add the same proportion of wood to the batch.

If the flavor is too strong or too weak, do another trial. There’s no reason to rush these wood-aged brews!

Although Crooks doesn’t use these alternatives at the brewery, he says brewers are “are making amazing products using oak spirals in glass or in carboys,” and that brett successfully ferments in all kinds of vessels, from massive stainless-steel fermenters to corny kegs.

While the dream of a home barrel program may still be out of reach, these barrel alternatives give homebrewers a realistic way of replicating flavors.