Thursday, October 11, 2012

What Is 100% Brett Beer?

You'll see. Keep reading.

You may have heard of Brettanomyces. The rogue of the brewing world, Brett is a wild yeast that's known for creating funky, wild flavors unlike nothing else, and for often showing up even when it's not wanted. Maybe you've heard the term "100% Brett" beer, and thought: "does that mean there will be 100% more funk?"  Or maybe you just drank a Brett beer that didn't taste like you expected, and turned to Google to assuage your curiosity. Perhaps, right now, I can hopefully explain a few things about 100% Brett beers that you did not know.

You see, 100% Brett beers are one of the great paradoxes of the brewing world; they don't work like you'd expect them to. The term seems to imply "more," right? I mean, if you brewed a 100% rye malt beer, you'd expect it to fully embody the flavors of rye. If you brewed a 100% wheat beer, you'd expect it to be more... wheaty. If you're brewing a beer with 100% Citra hops, it's probably because you want the flavor of Citra to come through as clearly and strongly as possible. You want to isolate those flavors. It's common sense.

But Brett does not work like this. Drink an All-Brett golden strong ale and a regular Belgian golden strong ale side by side and you might not be able to tell which is which. Drink a dry, yeasty saison next to a light, tart 100% Brett ale and you might say the saison has the same amount of funk — just a different kind of funk.

This is pretty well established — no brewer of 100% Brett beer will tell you that they come out ultra funky. But I can't say it's a commonly-known quirk of the yeast. I've heard well-versed beer aficionados who are still confused about this, referring to a beer that tastes too clean as "not funky like a 100% Brett beer." Partly, I think it's because there's no established beer-language to separate these sub-styles, no genre terms to differentiate beers in which Brett is used in different ways. And, it's unfortunately not intuitive; it goes against common sense.

In most Brett beers — including sour beers, where there are a number of other microbial players at work — Brettanomyces creates its funky, barnyard flavors over many months. A non-All-Brett-beer is fermented with a 'normal' brewer's yeast (Saccharomyces) in addition to Brett — the brewer's yeast does most of the work, eats most of the sugar, and finishes quickly. Brett, though, works slower. Think of Brett as if it's invading the beer, in this case. As a wild yeast evolved to eat wood sugars, Brett is able to eat more complex sugars than regular yeast, and so it tends to dry out a beer over time — not completely, but it'll knock off a few gravity points. It takes a while to do this, because it's working in a beer that was otherwise finished fermenting, and this stresses Brett out. As you may be aware, when yeast are stressed, they fart out more flavor... but usually undesirable flavors. Stress out a Belgian yeast, and the beer will probably end up tasting like cloves and band-aids. Stress out an English yeast, and your beer could become cidery and medicinal. But when you make Brett work for it — in a controlled, deliberate environment — you will hopefully end up with a beer that tastes like the ripe summer fields of God's own pastures (...or goat farts, if you're unlucky, but hopefully God's Own Pastures.) Brett needs very little to work with, because in return, it will work very hard to deliver its beautiful rewards.

So that's one way of doing it: a mixed fermentation with multiple yeast. But in recent years, brewer's have realized you can ferment just fine with All Brett. Pitch only Brett to a beer and fermentation will proceed much as if you had pitched a regular brewer's yeast. Rather than six months, your beer will be finished in three or four weeks. Attenuation is still high — 80 to 85%, around what you'd expect for a saison or Belgian yeast — and flocculation is low, but the Brett will go to sleep after that; the beer will not change very much between two months and a year. There might be some mild funk; or maybe not. In my experience, with my own 100% Brett beers and the commercial examples I've found, an all-Brett fermentation produces flavors much closer to a fruity, tangy Belgian strain. There's little barnyard to be found unless you're searching hard for it. How does this make sense? Shouldn't more Brett produce more flavor?

It may seem paradoxical at first, but deeper contemplation may reveal why 100% Brett beers taste simpler and cleaner than a Brett-invaded beer. Think of Brettanomyces as a bear. Brett is the bear of the brewing world: wild, unpredictable, relentless, insatiable. Have I mentioned that Brett is so hungry when added as an invading yeast that it will eat nutrients from dead Saccharomyces cells? It leaves a trail when it's on the attack: eating other things and turning them into Brett byproducts. Force Brett to work for its food, to go on the attack, and it will get aggressive and crazy. But if you just give it a pile of food all to itself — no other bears to compete with, nothing to attack, nothing to invade — it will remain pretty chill. It'll eat up all its food and not do a whole lot else. Since it finishes quickly, and doesn't have to eat scraps, there's no reason for Brett to fart out its delicious aromas over the course of months. It's going to take a nap, instead. While there will always be something unmistakably feral about it, you might even begin to mistake it for a cuddly, huggable lil' Saccharomyces strain.

So what if you let a 100% Brett beer hibernate for a year, or two years? Will more funk come out? Yes, most likely, although not to the same extent as a Brett-invaded beer. In this space, I will add links for each 100% Brett beer that I brew, and a short indication of how they're aging.

100% Brett Berliner Weisse - Brewed December 2011. Drank last bottle at 13 months old. Tartness became more pronounced over time, but never developed any significant funk.

100% Brett Belgian Golden Strong Ale - Brewed May 2012. Subtle funk developed over time, as of nine month old tasting. Drinking slowly; will save some bottles to age for a few years.

100% Brett Trois White IPA - Brewed August 2012. Drank mostly fresh; saved two bottles for aging. Intense tropical fruitiness, some Belgian-y character, no funk in early tastings.

100% Brett Trois Belgian Pale Ale - Brewed September 2012. Drank most over six-month period; no funk in that time. Tart berry character and tropical fruitiness. Handful of bottles saved for aging.

100% Brett Trois Imperial IPA - Brewed March 2013. Drank over one month period. Tart berry, grapefruit, intense tropical fruitiness merged with hop character.

100% Brett Belgian Dark Strong Ale - Quad-like recipe with blend of Brett strains. Split batch to determine effects of oxygen exposure on acetic acid production while aging.

100% Brett BKYeast C1 / C2 - Test batch split between two Brett strain isolates from BKYeast.


  1. Hi! Found this a year later -- very impressive set of experiments.

    Have you posted any recaps of what you've learned with these beers?

    1. Thanks Gail!

      I don't have a general recap covering all my batches, but I have posted results from a number of different 100% Brett batches since. Probably the most relevant are the results from this experiment where I tried to see if I could get Brett to create more acetic acid by leaving half of a split batch partly exposed to oxygen for a few weeks. Here are the notes for that:

      If you click on the "Brett beer" label, it should also pull up the posts for every one of my Brett beers. There have been a bunch!

  2. Heer van Biesen. 100% Brett. Belgium. Great beer!


Related Posts-