I remember my earliest days of homebrewing, when—although I had only a handful of all-grain batches under my belt—I really wanted to make a sour beer. At first, it looked like a daunting process that would require years of time to invest in an unknown outcome. Then I found a recipe in a magazine for a quick version of a sour red ale that called for food-grade lactic acid and cherries. While I was excited to taste the finished beer, the results were nothing like the Rodenbach I wanted to emulate.
Plainly, our understanding of acids and quick-souring techniques has evolved considerably since then. Today, we have many ways to employ acidity to craft great beers.
Although my first experience with adding lactic acid to a beer was rather one-dimensional, innovative brewers are successfully using acid additions to tweak the flavor profiles of their beers. The key here is restraint. It also helps to use a blend of different acids, so that the additions aren’t identifiable but blend into the overall flavor profile. Also, you can tailor the blend to any added fruit to further boost its flavor impact. (Here’s a chart of acids naturally found in various fruits, to help inform possible blends.)
Brant Butler, head brewer at Shred Monk in Bozeman, Montana, shares a process he used at a previous employer to improve their fruit beers. Unhappy with his kettle-soured beers because of poor head retention and off-flavors—such as the dreaded Cheerio-like THP aroma—Butler devised a method to blend acids that would mimic the acid content of a fruit addition, blending it into the flavor profile without calling attention to itself.
For a 15-barrel batch, they would add a variable blend of citric, malic, and lactic acids to the whirlpool—that would drop their pH to about 4.2. They’d pitch a Chico-type yeast strain (SafAle US-05), which would ferment it to about 3.8 pH. Then the fruit addition would typically drop the pH to 3.3 or 3.4. “Sometimes, we’d adjust with the addition of one of the acids, if it wasn’t quite where we wanted when we transferred to the brite tank,” Butler says. ‘This technique resulted in a sour beer [that had] no THP aroma, didn’t tie up a brewhouse vessel for extended periods, and still had head retention in the finished product, which we found was difficult to maintain with traditional kettle souring.”
At Deschutes in Bend, Oregon, the brewers have experimented in-house with various acids to better understand their flavor profiles and how they interact with beer. “This started with some explorations into pH adjustments and how they affect hop perception using citric, malic, and tartaric acids,” says head pilot brewer Jeffrey Johnson. “From there, we started to experiment with how these acid blends can be used in a wine-inspired IPA that features grape-like hops, such as Hallertau Blanc and Nelson Sauvin.”
The result of this work was a one-off taproom release, Winemaker’s IPA. According to Johnson, they added acid to the tune of about 6.8 grams per gallon (3.8 liters). The blend was a fairly even mix of citric, malic, and tartaric acids. “This dropped our pH to 4.1,” he says. “We found this blend gave the most depth of flavor—definitely gave it that wine-like character.”
The no-boil souring method starts like kettle-souring, but then the brewer skips the boil altogether and pitches yeast into the souring wort.
Necessity was the mother of invention for us at Jessup Farm Barrel House in Fort Collins. Post-sour boiling wasn’t an option. Cofounder Jeff Albarella explains: “We don’t ever go back to the kettle,” he says. “Our quick-sour goes through the hot lactic fermentation, and then we barrel age it.”
Albarella sours the wort in a fermentor with a pure culture of Lactobacillus casei. Over about 72 hours, the temperature drops to about 80°F (27°C), then he pitches saison yeast—the Brewing Science Institute’s S-26 Farmhouse Ale strain, which he likes because “it has a nice tropical-fruit ester profile in that environment.” Once primary fermentation begins to slow, he matures the beer for an additional three months in barrels on our house Brett strain before eventually adding fruit.
At Georgetown Brewing in Seattle, Barbara Beaver takes a similar no-boil approach—but she turns it on its head. “Any time I make a fruited sour, I throw a pitch of straight Lactobacillus in with the fruit and let it sit for at least a couple of days in the fermentor,” she says. That lactic fermentation is happening on only single-strength fruit—not concentrate. “I’ll then knock out wort and pitch yeast. I can taste how tart it is immediately at knockout. I also like this method because the hops control the Lactobacillus and essentially stop acid production.” She says she likes heterofermentative Lacto strains, especially brevis, because they tend to be hardier and quicker to acidify. She also says that this works best with low- to medium-acid fruits, since low pH (i.e., higher acids) also will inhibit the lactic fermentation.
Yeast Strains That Produce Lactic Acid
One of the newer methods of making a tart beer is using a yeast strain—Lachancea thermotolerans—that produces lactic acid as a by-product of fermentation. This option became more widely available commercially in 2019 when Lallemand released a strain found west of Philadelphia as WildBrew Philly Sour. This is fast becoming a viable alternative to kettle-souring, although it has a reputation for stalling out during fermentation. It has its own fermentation kinetics that need to be considered to get full attenuation in a reasonable amount of time. Since it produces most of its acidity in the first 24 to 48 hours, some brewers are pitching a second strain about midway into fermentation to speed things up. (See “Lachancea Best Practices,” below, for more tips on getting the best performance from WildBrew Philly Sour.)
Guggman Haus Brewing in Indianapolis is one brewery that has used the Philly Sour strain in their goses and fruited sours. Derek Guggenberger, cofounder and operations director, says they have had to work around the dreaded stall. “We … tried under-pitching, over-pitching, starters, etcetera,” he says. “And no matter what, at roughly Day 3 or 4, it basically [stopped]. So what we do now is we under-pitch it quite a bit, and by Day 2 it has already produced enough acid to drop the pH to 3.2 to 3.5. At that point, I’ll usually add a large pitch of rehydrated SafAle US-05 to help carry the beer to a quicker and more consistent finish. There doesn’t end up being a difference in flavor that we can tell.”
For those who want to avoid the stall, there is another option: Lallemand Sourvisiae. This is a genetically modified Saccharomyces strain that has a lactate dehydrogenase gene. It produces high levels of lactic acid.
“It was incredibly quick to drop pH in the fermentor,” says Hutch Kugeman of the Brewery at the Culinary Institute of America in New York City. “The pH was down from 5.3 to 3.96 the next morning, down to 3.2 by the morning of Day 2, and 3.15 by the morning of Day 3. Flavor profile is very clean and very acidic.” While the strain is easy to use and won’t tie up a kettle for long, the beer can get quite sour quickly.
With both strains, brewers may notice a lower apparent attenuation when measured with a hydrometer. According to Lallemand, this is due to lactic acid increasing the final gravity numbers and not necessarily to truly low attenuation.
Further Adventures to Come
If necessity is the mother of invention, then curiosity might be father. Sometimes, brewers need to go outside the box to solve a problem. At other times, they’re attracted to that famous question: “What if …?”
Either approach can open new doors of knowledge and, ultimately, lead to new and interesting beers. After all, they’ve taken us this far. No doubt brewers will develop more ways to nail that perfect amount of refreshing tartness in their beers or to make those fruit flavors really pop. Cheers to that.
Common Types of Acid in Fruit
Titratable acidity (TA) is a way to measure how intensely an acid is likely to be perceived, as compared to acetic acid.
Equivalent TA: 1.0
Acetic acid is generally produced in small quantities in traditional sour beers by Acetobacter or sometimes Brettanomyces and Lactobacillus, depending on the strain and conditions. Although acceptable at low levels, it is harsher and more distinctive than lactic acid.
Equivalent TA: 0.94
Citric acid is the most common acid in citrus fruits. Sourness is perceived as a bright, sharp acidity of a short duration.
Equivalent TA: 0.67
Lactic acid is the most common acid in both “quick” and traditional sour beers. Produced by Lactobacillus and Pediococcus, it is also found in many foods. Lactic acid is considered a weak organic acid, with a softer flavor that is more persistent in duration.
Equivalent TA: 0.90
Malic acid is the most common acid among all fruits. Malic acid has a more prolonged sour sensation, which increases its apparent sourness. In winemaking, excessive acidity can be reduced through malolactic fermentation, which converts malic to lactic acid.
Equivalent TA: 0.80
Although typically associated with grapes and cherries, tartaric acid is found in higher concentrations in tamarind. The perception is strongly acidic followed by an astringency absent from most other acids.
Lachancea Best Practices
Courtesy of Lallemand Brewing, here are some tips for getting the best performance out of the WildBrew Philly Sour strain (and avoiding a fermentation stall).
- Ferment it warm: For best results, ferment at 72–86°F (22–30°C).
- Pitch enough yeast: At those warmer temperaturess, pitch 10–20 grams per 5 gallons (19 liters). At cooler temperatures, increase the pitch rate to 20–30 grams. (Note: Philly Sour is available in 11-gram packets.)
- Give it time: Lachancea ferments more slowly than Saccharomyces. Given time, it will fully attenuate.
- Don’t co-pitch with Saccharomyces: The Sacch will outcompete it. If you are adding a second strain, wait until midway through fermentation.
- For more acidity, give it some sugar: The yeast first consumes glucose to produce lactic acid, so higher glucose levels will result in higher acidity. Add glucose early; late sugar additions may not be completely fermented because of high flocculation.
- One-shot deal: Lallemand doesn’t recommend re-pitching or bottle-conditioning with Philly Sour.
For much more from Gordon Schuck on ways to acidify your beers, check out his video course on Quick Souring Methods, available to All Access subscribers.