The Acid Zoo
Hinga Dinga Dergen,
The nascent craft beer industry’s first few surprises, back in the 80s and 90s, may have been hoppy chimeras that have since dominated the craft beer market, but I personally have a large soft spot for the sour beers that have sprung up in the last few years in particular. From kettle-soured Berliner Weisses (pronounced vice-uh, fun fact; no e’s are silent in German - or, at least, Hochdeutsch), to wild sours and Lambics aged over the course of years, an incredible variety of sour beers can now be purchased from any half-decent bottle shop. But whence exactly that tartness? (Whacky sentence, right? Trust your audience, they say.)
Clearly this acidity is a far cry from the combination of, say, citrus and clean lagers, and as it turns out, there’s a laundry list of organic beer acids, from the Carbonic acid produced by carbonating these beers in and of itself, to the gnarly, assertive funk of Isovaleric and Butyric acids, and all of them have a role to play in our favorite complex sours, whether we want some of them there or not!
The Good
The heart and soul of all popular sour beers that I’m aware of are twain (trust!): lactic acid, and acetic acid. These acids, when not wildly overdone, provide a bracing and refreshing acidity that buttresses (trust!) the spritzy allure of tart beers, particularly in warm weather. The vastly more important of the two, however, is lactic acid, so we’ll start with that.
Derived from the latin lac, or milk, lactic acid is probably best known to the yogurt- and sauerkraut-eating world as the acid responsible for the tang in those wonderful fermented products. In both of those products, as in beer, it’s the predictably named Lactobacillus genus of bacteria that’s to be blamed (really, thanked) for the resulting tartness, and it’s this very same (and super fast-acting) bacteria that’s utilized in sour beer brewing, in particular, and often as the exclusive source of acidity in kettle-soured beers.
(Kettle-souring, by the way, is rad - instead of boiling the wort after mashing right away [the step after the grain-soak, the “mash”], you toss in some lactobacillus while the wort’s warm and wait 24-72 hours, after which the wort is somewhere between refreshingly and mouth-puckeringly tart)
The other pseudo-main acid in sour beers is acetic acid, and as far as I’m aware, it’s virtually always meant to take a back seat to lactic acid. It’s the same acid that’s prevalent in vinegar, and in fact you can make what’s referred to as “white vinegar” by literally just combining water and acetic acid. As you might expect, acetic acid can be a bit...aggressive when left unchecked, but it can add a nice earthy, funky layer of complexity to a Lambic or a wild ale, and it’s a note that, beyond Brettanomyces funk (not sour! Not gonna talk about it!), I most often identify in non-kettle-soured beers. My esophagus doesn’t love it, but I’m a fan on a culinary level.
The Bad and Ugly
While kettle-soured beers are often refreshing and pleasantly tart, and while they’re clearly good enough for the vast majority of beer drinkers (keep an eye out for any Goses or fruited sours next time you’re at a bottle shop for vivid proof of this), they’re often dinged by purists for lacking complexity, and that’s due to a number of “missing” notes, but as far as Butyric and Isovaleric acids go, that’s not a bad thing.
The former is a very unpleasant, very pungent acid almost always classified as an off flavor and very often associated with poorly made homebrew, and is often described as smelling like “baby vomit.” Yikes. Needless to say, we don’t make wild ales, and one of many reasons is the fact that every time you brew a truly wild ale (that is, brew lightly unhopped wort and just...kinda leave it out in the open, for whatever’s in the air to go to town in), you gamble that the majority of bacteria and wild yeasts make beer that tastes, ya know, good, and there’s no guarantee you won’t make a beer that has this pronounced and universally panned acid in it.
Less egregious is isovaleric acid, which is described as smelling like “pungent cheese or foot odor.” Yikes. A very low level cheesy vibe probably wouldn’t ruin a wild ale - I find champagne to have a vague rindy cheesiness to it - but, yeah, you’d want this to be a back note. Like way, way back.
Fine Print
Naturally, there are a ton of organic acids out there, though in the beer context, a number of these other acids are relatively tame, or simply present in all beer, but hey, let’s talk about them anyway!
The two obvious acids you’ll find in all beer are Phosphoric (and Phytic) acid and Carbonic acid.
The former are Phosphorus-based acids, and both are fairly neutral-tasting acids that are big players in the mash pH game (don’t...just, just don’t worry about what that is or means). The former, Phosphoric, is used to lower the pH of the mash, while the latter, Phytic, is an enzymatically-produced acid that the grain itself uses to store Phosphorus, and which can be teased out by performing the seldom-used “acid rest,” wherein the mash is held at, oh, 95˚-115˚F (versus its usual 140˚-155˚). Oh, and this is the chief acid in popular Colas, by the way - pretty subtle stuff, right?
Carbonic acid is, amusingly, no more than the acid produced by dissolving CO2 in water - it’s the zip in Seltzer, in other words. And as you can imagine, it’s present in virtually all beer - perhaps all beers, even the flat ones, given the near-impossibility in completely removing it from beer once you’ve added it.
(There are a number of other acids produced by yeast, and hence common to all beer, but we’ll leave those for the studious among ye.)
Finally, as a bonus of sorts, we have citric acid, which is almost entirely absent from all beers that aren’t explicitly citrus-based, but which homebrewers apparently used to use to adjust mash pH - pretty nuts!
Conclusion
If I’ve learned anything from writing this insane blog, it’s that if you zoom in on literally anything, an endless font of arcana and esoterica pops up (trust!), and the acidity in beer is no exception. Let’s both count ourselves lucky that I haven’t taken Organic Chemistry yet!
Cheers,
Adrian “Tartlord” Febre