THE ACID ZOO, PT. 2
Hello and Welcome,
Two weeks ago, before I was so rudely interrupted by our anniversary, we were talking acid and beer, and while we covered the types of acids that give our favorite Cherry Goses and low-ABV Berliner Weisses their zing, we never actually discussed how that acid got there (for the most part), so this week, we’ll be doing just that.
And as last week we started our conversation with the microbial world, so too will we start this week.
Whence the Sour in Sourdough
As we touched on last week, the primary acid in most (all?) commercial, non-funked sour beers is lactic acid, the same acid found in sourdough and yogurt, and a delicious byproduct of, principally, lactobacillus. This bacteria genus is fantastically versatile when plunked into wort, equally happy ripping through sugar in order to turn mellow wort into a puckersome brew in as little as 24 hours, as in a Belgian Gueuze aged over the course of years. While it’s present in most (all?) wild-fermented beers, it’s also the sole souring agent in most (all?) kettle-soured beers (a process where, before boiling but after mashing, you add bacteria to your sugar water where they produce your beer’s acidity, after which you boil your wort, killing those hardworking microbes), which means you have it to thank, until very recently, for the most (all?) of the Goses and Berliner Weisses on American beer shelves (since the vast majority of those, for economic reasons, would have been quickly soured).
Among those, I’m honor-bound to mention, Lactobacillus Plantarum is probably the most widely used, and indeed the sole bacteria strain I turn to when kettle souring. It’s wicked fast.
The demand for, and premium placed on, sour beers in recent years has yielded a scientifically-produced alternative, however: normal ale yeast strains that have been genetically tweaked to produce lactic acid. This is a massive boon for several reasons, chiefly: your yeast is much more likely to be happy in an acidic environment if it’s the source of the acidity, whereas standard ale yeasts aren’t too happy below a pH of 3.5, which I’ve regularly undershot with kettle souring; the process of kettle souring can take multiple days, which is a long time to tie up a boil kettle, and these yeasts avoid that issue, while also speeding up the process generally; and if you were to put a non-pasteurized sour beer on tap, you’d permanently funk up those lines, whereas the word is you can run sour beers created with these new yeasts on a line and then swap back like nothing happened, which is a huge advantage to small breweries.
Beyond Lactic Acid, again, Acetic Acid plays a strong secondary role. The chief producer of this acid in beer is, you guessed it, Acetobacter, and while it’s seldom (never?) present in kettle- and quick-soured beers, it’s present in a huge number of traditional and aged sour beers. An entire post could naturally be written about this lil’ pup, but I’ll toss in but a solitary anecdote: in order to brew maximally flavorful sour beers like those soured in part by Acetobacter, brewers often produce “turbid mashes,” wherein they employ unmalted grains as a portion of their grain bills in order to leave long-haulers like Acetobacter complex sugars, dextrins, as a food source during the long winter that is sour fermentation.
As a last stop on this micro-bus, we have the zoo of bacteria and wild yeasts that comprise the fermentation team in wild-fermented beers. These dudes produce a range of acids, some of which we discussed last time, and perhaps as notably a wide range of esters, some great and some...less so. The Kveik king’s insanely cool lecture made a fascinating claim about these esters, namely that they’re compounds produced by wild yeasts whose purpose could quite possibly be the neutralization of natural organic acids found on, say, trees, as a defense to said bacteria and yeasts, and whose more flavorful subsets we’ve kept in our artificial selection of yeast over the years. What a concept.
Acidity in the Modern Era
While the use of living things was our only method of souring things for, like, the vast majority of recorded time, industrialization and science has produced a potent alternative in recent years: food-grade acids.
The first of these to be used in brewing was probably something like Star San, a no-rinse sanitizer that uses food-grade acids to nuke whatever bacteria and yeasts happen to land on or in your fermenters before you rack your (hopefully decent-tasting) wort and fresh yeast into them. Beyond this, and probably thanks to the modern candy industry, if I had to venture a guess, various acids have been used over the years in homebrewing to adjust the pH of the mash (which is important for a number of reasons, none of which is worth explaining; one of which is flavor, though), and in some cases to make “fake” sour beers without kettle souring.
Early on, this pH adjustment (which for years was far and away the more common use of commercially produced acid in beer) was done with such far afield choices as Citric Acid (the acid in, yep, citrus fruits - jokes aside, in general it’s the older and more human-experience chemicals that have the more obvious names, meaning vinegar, citrus juice, and yogurt bacteria and acids all have “normal” names), though today Lactic acid is occasionally used, and Phosphoric Acid is king - see the last post for more on that.
But now, as sour beers take off, a few companies have started producing flavorful blends of acids for use in “fake” sour beers; heck, we’re even in on the party, using one such blend for a recent staff batch (that wonderful Ambrosia beer), which we’ll be brewing full-scale ASAP. This is far and away the easiest move, since you don’t even have to change your house yeast to produce market-ready Goses, especially fruited ones (whose flavors hide the subtleties of the base acids anyway), and I suspect it may eventually oust those acidity-producing “normal” yeast strains eventually, leaving just itself and the complex-tasting-by-comparison kettle souring process.
Bonuses!
That covers the gamut of sources of acidity in modern brewing, in a nutshell, but there are two other topics worth mentioning.
The first is a somewhat radical German technique for adjusting pH without using Reinheitsgebot-violating commercial-grade Phosphoric Acid, or the time-consuming Acid Rest: Sauergut. The basic idea is to create a lactic acid, sour beer concentrate using the same wort you’d use for a Pilsner, say (minus the hops), and then to rack a small amount of this turbo-Berliner Weisse into your mash in order to lower the pH. The crazy part of this story is that, as a consequence, there should be some traditional German Lagers out there with a touch of Lactic Acid, which is insane to me.
The second, I’d be remiss to omit (trust your audience!), is a semi-domesticated “wild” yeast frequently found in traditional sours: Brettanomyces, or “British Fungus,” named for its initial discovery in British beer, if memory serves. It produces really interesting flavors, ranging from tropical fruits (particularly pineapple) to “Horse Blanket,” and can even be used as your sole yeast. I once had an insanely good Porter made this way, though when I brewed it myself, the result was...acceptable. It’s a bit of a risky play.
And the reason it’s not so big of a note in even sloppily-produced fresh beers is that, when employed alongside normal yeast, it can take months to “present,” which is part of the story behind Mild Ales, but that’s a different post. I may have even written it, who knows! Check the tapes!
Conclusion
If you’ve only ever had modern Goses and fruited sours, you’d think it’s fairly straightforward to get acidity into beers, and while that can certainly be the case, there are some beers, like Oude Bruin and Gueuze, that are so tough to make that I doubt I’ll ever even try, and it’s just such beers that are, thus, perhaps more worth grabbing and trying than almost any other beer. Oh, and we may not have anything sour on tap now that we made, but stay tuned for that rad Ambrosia Sour! Give us, like, two months!
Cheers,
Adrian “Pucker Up” Febre