100% Brett beers offer an interesting opportunity to test out Brett strains without the extended aging period that Sacch-fermented, Brett-invaded beers generally require. The flavor profiles of these beers can be quite similar to your standard Belgian beers, but can also quickly spin off into something very unique, and generally unexplored. One common misconception is that Brett will make all beers funky, or even sour. This isn't necessarily true. It's actually rather difficult to bring out a lot of funk from a 100% Brett beer, but given that, where does the idea that Brett creates actual sourness come from? My guess is that a lot of people get confused due to Brett's important role in sour ales and spontaneous fermentation. However, most brewers making 100% Brett beers will get tartness at most, but never anything so bracingly acidic as even a mild sour ale. (It's why strains like Trois can be so good in hoppy beers).
However, there are may be a caveat to this — something of a loophole. Part of the information lacking in my understanding of Brett is its relationships to oxygen exposure. Brett seems to behave strangely around that little molecule, eating it up and preventing oxidation, and perhaps even taking O2 and using it as fuel to spit out acetic acid. But to what extent, and under what conditions, does this happen?
I have long wondered why/how 100% Brett fermented beers like Surly Five and Deschutes' The Dissident are said to be sour, despite what those breweries reveal about their fermentation process (there's no mention of any bacteria at work despite the barrel aging process). Either the brewers are leaving some information out, or they somehow created quite strong 100% Brett beers that are described by many drinkers as sour, acidic, as well as tart. And consider this: historic styles such as Adambier and English old ale were known to sour considerably over time, despite both high ABV and IBUs that should have inhibited souring bacteria. Being that Brettanomyces is known to create acetic acid given the right oxygen exposure, is it possible the barrel aging gives Brett the extra kick it needs to produce acetic compounds — which wouldn't happen in a homebrewer's carboy — resulting in their perceived sourness?
Since I have never actually tried Surly Five or Deschutes' The Dissident myself, I had no interest in attempting a clone of any particular beer with this one; my recipe was designed as a "Belgian dark strong ale" under the belief that a darker, maltier, stronger beer would simply go better with the slight vinegary character I may or may not achieve. One year ago, I brewed a 100% Brett fermented Belgian golden strong ale, and it had always been my intention to brew a complimentary dark cousin to that beer; two halves of the same coin, showcasing two sides of what Brett is capable of with different grain bills.
Since I do not have a barrel, my experiment involves splitting this batch in two. One half (two gallons) goes into a carboy with an airlock, where it will ferment and age like any other batch. The other half (also two gallons) goes into a second carboy which, instead of an airlock, received a foam stopper covered with tinfoil. The foam stopper and tinfoil will keep out any unwanted nasties, but will also allow the beer to receive a steady amount of oxygen. How much? Too much? It's hard to say. That's why this is an experiment, and why I split the batch in two. I imagine that, despite the foam stopper, the beer will be covered in a blanket of CO2 for some time, and will hopefully not become oxidized as if I had shaken it aggressively post-fermentation. I can already note that, about two weeks from brew day, the O2-Exposure portion has formed a pellicle, while the airlock portion has not... which isn't surprising. I'm expecting that Brett's ability to form a pellicle will help regulate oxidation in a way that no Sacch strain could do; also consider that in a barrel, O2 exposure leaks in from all sides, so a pellicle would do less to limit oxygen exposure during the barrel-aging process.
I will taste both portions frequently to check their progress, but my hope is to find a moderate sourness developing in the O2-exposure half after a few weeks, at which point I will probably pop an airlock on the sucker, or just bottle it.
One other variable going into this batch: I found a couple of jars of mulberry molasses at an Indian grocery store in Manhattan, and decided they would make for an interesting, complimentary pairing to this beer. So those are going in to keep the beer from getting too heavy — basically the same philosophy as candi sugar in a standard Belgian beer. I'm hoping for a nice subtle fruitiness and tart berry character that will compliment a dry, acidic, yet also malty and fruity-tasting beer. With this batch, I am also experimenting with a mix of Brett strains: Trois, L and C. Trois is a bit too fruity / not enough funky for my goals here, so I'm hoping L and C provide some more classic funk character, as well as add some complexity and variation to the acetic acid formation — if that little part of the experiment works at all.
Update: Tasting notes for this batch have been posted here.
4 Gal., All Grain
Mashed at 147 F degrees for 75 minutes
Fermented at 72 F, ambient room temp
(due to weird sugar additions, I'm giving the grain bill in pounds instead of %)
5 lb. 2-row malt
2.5 lb. Munich
8 oz. aromatic malt
8 oz. Special B
2.4 oz. chocolate wheat
1 oz Northern Brewer @60 min
2 oz Belma @1 min (+20 min hop stand)
White Labs Brett Trois
White Labs Brett L
White Labs Brett C
White Labs Brett Trois
White Labs Brett L
White Labs Brett C
4.21.13 - Split batch between two 3 gal. carboys. Pitched Brett L + C + Trois
Visible fermentation by next day
4.23.13 - To each carboy, added 0.5 quart water with 8 oz pasteurized mulberry molasses. Mixture at 13.9 Brix. Also added .3 oz medium toast American oak cubes mixed with light toast oak chips to each carboy.
5.3.13 - Each carboy at 1.010 SG. Noticeable flavor variation.
5.9.13 - To each carboy, added 0.25 quart water with additional 8 oz pasteurized mulberry molasses, plus 2 oz dextrose sugar. Added additional .2 ounces light toast American oak chips.
5.13.13 - Put airlock on "02" version to limit continued exposure. Received approximately 3 weeks "open" carboy O2 exposure.
6.15.13 - 02 version at 1.008; Airlock version at 1.009. Both extremely dry, tannic, like dried fruit skins. O2 version exhibits mild acetic character. Airlock version noticeably fuller, sweeter. Mild earthy / fruity funk from both.
10.17.13 - Tasting notes here.