Schell’s Jace Marti Goes All-In on Authentic Berliner Weisse

Jace Marti, assistant brewmaster at August Schell Brewing in New Ulm, Minnesota, is both a serious student and a brewer of authentic, mixed-fermentation, Berliner-style weissbier. Here is some context on the style and details on Schell’s methods, including lots on Brett and those big, beautiful cypress tanks. As told to Joe Stange.

For more on Berliner weisse, including a Style School article by Jeff Alworth and a recipe from August Schell, watch for our April-May 2021 issue—or subscribe now.

Which Berliner Weisse?

I think American brewers’ interpretation of Berliner weisse has a lot to do with that Winston Churchill saying, “History is written by the victors.” By the time craft beer was booming in the United States and brewers had begun to really explore sour beers, all that was left of Berliner weisse in Germany was Berliner Kindl Weisse.
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I’m not going to say anything bad about Kindl, but it is not produced in the traditional manner—their bottles don’t actually say, “Berliner Weisse,” but rather, “Kindl Weisse.” So when brewers looked to Berlin for a classic example, the only thing available was this extremely acidic, non-Brett version. Combine that with the historical element: Kettle-souring—the Francke acidification method from 1906—was well documented; it was easy to put the two together and assume that’s how they were made.

There is nothing wrong with kettle-soured beers. But I think trying to produce a classically made, mixed-fermentation version of Berliner weisse is absolutely worth attempting. I thought about this for a long time—about how to wax poetic about what makes a classic Berliner weisse so special—but I decided to leave that to late, great Michael Jackson: “If there is a Champagne of beers, it is definitely Berliner weisse, with its unusually pale color, sustained small head, intense sparkle and, especially, its fruity acidity. … It is the most quenching and refreshing of all beers, and one of the lightest. It is feminine, teasing, and complex, with no pretensions to great gravity.”

Grist for the Brett

The great thing about brewing Berliner weisse is that it can be as simple or as complex as you want. The malt bill is just wheat malt and pilsner malt. I prefer a greater percentage of wheat malt to pilsner malt because the wheat adds a subtle creaminess to the mouthfeel and better foam—but really, any combination of the two will work. Historically, some were even made with only pilsner malt.

If you can find it, you could use a little chit wheat or chit barley malt, as the lower modification will help with foam retention, but it’s not necessary. I like to use a decoction mash for our beers because it was traditional—but again, you don’t have to.

One thing I would stress is this: Mash for dryness. Often brewers think they need to leave a bunch of residual sugar for Brett to consume during secondary, but that’s not the case here. Brett is a scavenger, and it doesn’t need much. If it has too much food, it seems like it gets lazy and doesn’t really do much. It’s not until the Brett yeast cells get stressed out that they start producing the characteristic aromas we want. By mashing for dryness, you get to that point quicker. Run off a clear wort, too—no need to send a bunch of trub into your fermentor.

In the kettle, these beers are traditionally not boiled. Just bring it up to near boiling and hold for 20 to 30 minutes to sterilize the wort. Hop bitterness is extremely low: 4 or 5 IBUs. Use hop extract if you have it. It’s the easiest way get exactly the number of IBUs you want, since hops and bitterness take a back seat with this style. That’s not to say you can’t dry-hop it down the road after the beer has reached maturity. Brett does some really cool things with dry hops, so I would definitely encourage giving that a whirl at some point. And because Brett scavenges oxygen, you end up with a really stable hop aroma in the bottle as well.

Acidification

For us, acidification is a long-term goal. We do a pre-fermentation pH adjustment with aged beer—more on that below—to drop the pH into the 4.5 range, and by the end of primary fermentation, we are usually still in a standard beer pH range of 4–4.2, maybe 3.9 at most. Total acidity at this point is around 0.2 percent—very subtle.

For primary fermentation, we pitch a mixed culture of Lactobacillus brevis, Brettanomyces (bruxellensis, claussenii, or both), and our house Kölsch yeast. We chose the Kölsch yeast specifically because it doesn’t flocculate well—that’s part of the long game for the Brett, see below—and is pretty neutral. We underpitch the Kölsch yeast to give the bacteria a head start, but once we hit high kräusen by Day 2 or 3, primary acidification is pretty much done.

Once primary fermentation is complete, we transfer into our big cypress tanks without crashing, and then not a whole lot happens for a while. It’s not until the Brett starts breaking down the longer-chain dextrins and the Kölsch yeast goes through autolysis that acidification starts to pick back up. For a regular, classic example of a Berliner weisse, I prefer them in 3.4 pH range, with around 0.5 percent total acidity. I just feel like that strikes the right balance of thirst-quenching drinkability.

Adding Aged Beer

We’ve adapted what we call the “Schultheiss” method into our production process. What the Schultheiss brewery did that was really unique is they were constantly adding aged beer to freshly brewed wort in the fermentor. This served three purposes, as far as I know or can guess:

1. It was a way to help build flavor consistency from batch to batch. Making a mixed-culture sour beer with a consistent flavor profile is really difficult. This would have been a way to create some consistency over many batches and many years.
2. This kept the cultures going. While they also pitched a mixed culture at primary fermentation, there were, no doubt, some “house” cultures that existed beyond that. This was a way to preserve that.
3. This was a natural way to adjust pH at the start of fermentation. By dropping the pH into the mid to low 4s with a portion of aged, sour beer, they brought the wort of the new beer outside the range of proteolytic activity of the many heterofermentative bacteria they were using. This was a key element in preserving the infamous foam head that was a characteristic trait of historical versions.

This method is only really possible if you already have an aged stock of Berliner weisse from which you can pull. The procedure we follow is pretty much what they did. We do a benchtop blend on brew day with fresh wort and whatever aged beer we are going to use to determine how much we need to add to reach our target pH of 4.2 to 4.5, depending on the beer.

Why Brett Matters

Brett is really what differentiates a classic example of the style from a kettle-soured version—and it’s why Berliner weisse earned the nickname “Champagne of the north.” Brett lends a distinctly complex, fruity, and floral aroma that you cannot get with regular yeast. It also makes for a drier beer, as Brett breaks down some—but not all—of the more complex sugars in the beer. With that aroma and dryness and an elevated level of carbonation (also partly as a result of Brett), it’s easy to see how it drew comparisons to champagne.

We age our beers for quite a while in our cypress tanks before we bottle them, so the changes that happen in a bottle over time are more subtle. What I notice in our beers in the tank is, of course, the early onset of Brett, which often is a not-so-pleasant musty-earthy character—but that eventually gives way to the fruity-floral character we’re seeking.

For several months, we’ll notice the mouthfeel of the beer getting thinner and thinner as the Brett breaks down residual dextrins. Then—usually at around nine months to a year—the beer goes through a really bad stage where the primary Sacch strain dies off and goes through autolysis. That’s when the magic seems to happen. We send a fair amount of the primary yeast into secondary because we don’t cold crash—and because that Kölsch yeast doesn’t flocc well—so there is a pretty thick yeast cake at the bottom of our tanks. The Brett starts to use that for a food source, and that’s when the aroma and flavor take a turn for the positive. So does the Lacto, as we’ll start to notice the pH drop and the total acidity start to tick up after being fairly stable up to that point.

I think this is my favorite part: Glycerine from those ruptured yeast cells gets released back into the beer. This is when mouthfeel starts to fill back out, and the beer takes on this distinct sweetness that plays so well with the sourness. We notice the same thing happen in our bottles, but on a longer timeline—the bottle-conditioning yeast die off around Year 2, and the beer will taste sort of lifeless, or “past,” for lack of a better term. But once the Brett consumes those off-flavors, it livens back up and becomes much more stable again.

These beers are constantly evolving, and that’s what I think is so cool about them.

About Those Big Cypress Tanks

I think the cypress tanks are pretty cool, but they also contribute quite a bit to the beers we make. Even though the tanks are 85 years old, I still pick up a very subtle wood character—especially in the longer-aged beers—that the cypress wood still contributes. They also allow a little bit of oxygen ingress, which is beneficial for the Brettanomyces. We’ve done trials of the same beer in one of the big tanks and in a wine barrel, and the Brett character is totally different. The amount of oxygen the cypress tanks let in over time is much less than a smaller barrel, and that, I think, gives our beers a more subtle, delicate Brett character.