Thursday, May 9, 2013

100% Brett Dark Strong Ale (O2/Acetic Acid Experiment) - Recipe & Brew Day

100% Brett Belgian Dark Strong Ale

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?
Surly Five

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
OG: 1.083
FG: 1.007
ABV: 10%

(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

Hop Schedule-
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

Brew Log-
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.


  1. That's a pretty interesting grain bill what with the melanoidin, caramunich and aromatic malts. I think you did a good thing by making the color adjustment with Carafa III. It is a "Dark" Strong Ale after all. I'd probably keep some extra sugar/DME around on brew day just in case I didn't make it to the desired OG; you seem to be quite a bit better at maximizing efficiency than I am though.

    What sort of sour bugs are you thinking about adding to the 2.5 gallon portion?

    1. Yeah, I wanted to avoid it becoming too roasty, but I figured those malts would help get the "oud bruin" ish character that I'm aiming for. I almost always wait to add sugar additions during or after primary fermentation — that way the yeast is less stressed from the onset (with a lower initial FG) and they can tackle the extra sugar addition while they're already chugging away. It also means I can nail my target OG by just upping or lowering the sugar addition slightly.

      Both portions got the same Brett strains. No bugs are going in either. I want to see if I can get some acetic character out of Brett just from O2 exposure. Based on the samples I've taken so far, it does seem to be working!

  2. Good experiment. That seems like a ton of oak that you are adding to each carboy. Did they not taste like too much oak the last time you tried them?

    1. Crap, no, I'm just stupid. I forgot a decimal point! Haha.. ha.

      It's actually .3 and .2 ounces, plus some of the chips missed the carboy opening and fell on the floor (which is why I added the second addition). So each ~2 gallon split has, I'd estimate, a little under half an ounce in it total.

    2. Ahhh, that makes more sense and sounds about right. I think the oak was a good idea as it should give some perception of sweetness in this beer that will be so dry.

    3. Yeah, as of my last tasting, this was even drier than I expected. I hope it's not TOO dry, but it's how I prefer my 100% Brett beers. Many of the commercial 100% Brett beers that I've had were too sweet, with a cloying character that I think the yeast enhanced. So I hope you're right about the oak... they haven't tasted all that oaky so far, so I think both will probably get a few more weeks at the least.

    4. I actually have an issue of getting mine too dry because my 100% Brett batches were an experiment from a main batch. I did find that some wood sugar from the oak really helped. This was also confirmed by Chad at Crooked Stave. I was surprised at how balanced his beers were and he said they finish dry, but with the amount of oak aging the pick up wood sugars that change that perception.

    5. Interesting. I'm hoping I can strike that balance of sweet-vanilla oaky-ness without over-doing it. So far I haven't been fully satisfied with the oak character in my brews; you can tell they weren't aged in a barrel, and the flavor is just more "woody." This time I used a mix of chips and cubes, which I may have forgotten to mention, so I'm hoping that provides more depth.

      Chad just sent a shipment of CS beers to NYC, quite unexpectedly, and I was able to have a friend pick up four of them for me. So excited to try them.

  3. Just an FYI, Dissident does utilize bacteria for its sourness/tartness. I received this answer from the brewery when inquiring as to the Brett/bacteria contents of the bottle:

    "Glad you enjoy The Dissident. As far as Brett goes we use an equal amount Brux and Lambicus in our aging process of two years. A portion is in oak Pinot casks and a portion is in stainless. With the stainless we use staves in the tanks that are not getting cherries. We don’t want anything from the orchard to infect our staves because we get three uses out of them. The portion that is not getting cherries will have staves for the Brett to live on and added oak character. We grow a strain of Lacto Bacillus here at the brewery which we use in the mash and in the kettle. This becomes inactive in the kettle obviously, so other than the pH and the bio flavor it is not really used for conditioning.

    The Brett should still be active and possibly pitchable. So you will have a blend of Brux and Lambicus. I would recommend that you try to propagate the yeast back up. Add the yeast to 15 Plato wort, store near 75-80 degrees F and see if grows, if you have activity in 2 or 3 days, you can let it finish out and then pitch with that. If you don’t have a microscope to check viability just keep a good eye on it and if it really takes off you should be fine."

    I just made a 500ml starter from a small dreg sarter dregs that I'm going to step up to 1000ml and use in a Brett stout. I tasted the wort in the initial 200 or so ml fully fermented sample and it tasted great. Definitely tart and a great deal of cherry. Looking forward to using it in a beer.

    1. Thanks for the comment, great info! So basically it sounds like they do a very short sour mash and then let the Brett do its thing on its own. I've seen a few others use that strategy, and it's cool to see proof that it works so well.

      Good luck with the brew! Are you going to use a similar mash strategy?

  4. No problem. I was amazed when he sent me so much specific information. I'm more than happy to pass it along.

    I think I'm going to skip the sour mash. I'm not going for much tartness outside of what the Brett may or may not provide. The cherry from the L and some funk from the B sounds like it will go great with a stout. I have a Tart of Darkness-esque sour stout going with Roselaire right now too, so I'll have a ton of non-traditional stout to drink before too long.

    I'll let you know how the Dissident dregs do in the fermentation department. If I'm happy with how the stouts go, I might throw a barleywine on the cake or part of the cake.

    1. Yeah, it'll be interesting to see how healthy they might be yet. The Dissident is a pretty hefty beer, and from the sounds of it, they've got to hang around for a long time too. Since they use commercially available strains, I suppose you could always resort to buying the Brett to emulate the process.


  5. Very nice posts! I enjoyed reading them.

    I heard that the Bretts are really notorious for infecting equipment. I mainly use glass but for bottling I use a plastic bottle, I can have a second one. What are the rules of thumb when dealing with brett to make sure don't infect other batches.


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