There’s a wide spectrum of options these days for making beers with varying levels of acidity. Let’s consider that spectrum: On the most challenging, complex (authentic?) end, you might find spontaneous fermentation; on the easier, pragmatic (cheating?) end, you might find direct additions of lactic or malic acid to control tartness. Then you can imagine all kinds of things out in the middle, such as kettle-souring or co-pitching bugs with yeast.
As a brewer, you choose your comfort zone; we all have different tolerances for complexity, difficulty, and unpredictability. (Then there’s the straight-up hedonistic view: If it tastes good in the end, who cares how you did it?)
So, what about these new yeast strains that produce lactic acid (i.e., they are not Lactobacillus)? Where do they fit? We previously wrote here about Lallemand Sourvisiae—a bioengineered strain of Saccharomyces that produces enough lactic acid to bring your wort down to a puckering 3.0 pH … at which point, some blending might be in order. (For context, Belgian oude gueuze tends to land between 3.2 and 3.4 pH.)
The newest of these strains, also from Lallemand, is their WildBrew Philly Sour. It’s similar to Sourvisiae, in that it is yeast—not bacteria—that happens to produce lactic acid. In this case, it’s neither Sacch nor bioengineered but a species of Lachancea isolated from nature by the University of the Sciences in Philadelphia.
How it works: The beer should finish in the more moderate 3.2–3.5 pH range in about 10 days; its optimal temperature range is 68–77°F (20–25°C). The appeal is in its simplicity: one yeast to pitch, just as you would any other. Then you end up with, as Lallemand says, “refreshing acidity and notes of stone fruit.” It is also said to produce high attenuation, high flocculation, and good foam stability.
I received a sample from Lallemand, and I tried it recently on a 10-gallon (38-liter) batch of wheat beer—essentially a Berliner weisse wort, going for a svelte 3.5 percent ABV. I rehydrated and pitched the Philly Sour, then gave it two weeks to ferment at about 72°F (22°C). Sampling from the spigot a few days before we go to press, the beer is clean and lemony—softly tart, not sharply so. It’s simple but delightful—a lawnmower beer in the making, akin to a gentler kettle-sour.
Now that I’ve kegged half the batch, I’m pondering what to do with the other half, to add some wrinkles—maybe pitch some Brett, or add a load of fruit, or both—because that first part was just too easy.