How did they get Surly 5 sour? (interview with some clues)

I'm sure it's been posted on here before, but a couple months ago I read this interview with the brewers at Surly, where they talk about their process for Surly 5, the brewery's 100% Brett creation. Unfortunately, I've never had the beer myself, but I recall various posters (including the Mad Ferrmentationist) relating that it was surprisingly sour. Maybe the only sour 100% Brett beer they'd encountered.

Now, having gained more experience with brewing 100% Brett beers myself, this is really bugging me lately. How the hell did they get it sour? I mean, the consensus on here, in my own experience, and with any other commercial 100% Brett beer, is that even getting the beer to come out funky is rare. Much less sour. Are we missing something?

Here's part of their description: "Oxygenation is a huge thing too. The tricky thing is that when using Brett, leaving it in the tank is the safest thing to do. Rack your beer off it and then just put fresh wort in there. Every time you oxygenate it there’s more acetic acid, so it gets more sour every time. They don’t recommend trying to quicken the fermentation by oxygenation because you’re going to have a lot of weird stuff happen with a lot of acetic acid produced. We tried not to do that."

Again... has anyone else experienced that? I can't recall ever seeing another homebrewer report results like that.

In the interview, they also describe how they aged it in barrels, and the sourness only appeared after a few months of aging. Is it possible the beer was actually inoculated with bacteria in those barrels, thus allowing it to follow a typical souring path? Did the brewer's just not mention this part (or maybe not realize that it was happening, somehow?) I do remember Chad Yakobson (who would probably have some great insight on this.... cough cough) mentioning on a podcast that Brett can produce some kind of acid under certain conditions, so if this is possible, what exactly did the Surly guys do that most of us are missing?

Would love to hear some theories, or better yet explanations, if you've got 'em!

Dont kno how Surly does it but i sour by pitching lactobacillus into unhopped unoxygenated wort at 90 to 100F for 4 to 7days then cold crash and rack into kettle. Reboil adding hops as required per style and then pitching Brett

I cannot provide tips on how to get the sour, but I did drink 6 bottles of Surly 5. What a great beer that was. Much better than Syx in my opinion. It was aged in red wine barrels and to me that was the dominant flavor. It was not the sourest beer I've ever had, but it did taste a lot like a dry red wine.

othellomcbane said:

Is it possible the beer was actually inoculated with bacteria in those barrels

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This. No matter how much you clean the barrel, you will never have a 100% clean environment. Bugs can get pretty deep into the wood and survive.

I just read the interview. "As soon as it was done fermenting [in stainless] we’d rack it into the wine barrels." It sounds like they did primary in stainless, racked into barrels, but short filled the barrels. Then added highly oxygenated wort to the barrels. This likely encouraged the acetobacter in the wood to kick off acetic acid. They let it sour over a few months to the level they wanted and then bottled.

I didn't read that they add fresh wort in the barrels but it did seem like something else goes on in the barrels other than brett, whether they added bacteria or just relied on whatever was in the barrel and/or acetobacter to reach that level of sourness.

levifunk said:

This. No matter how much you clean the barrel, you will never have a 100% clean environment. Bugs can get pretty deep into the wood and survive.

I just read the interview. "As soon as it was done fermenting [in stainless] we’d rack it into the wine barrels." It sounds like they did primary in stainless, racked into barrels, but short filled the barrels. Then added highly oxygenated wort to the barrels. This likely encouraged the acetobacter in the wood to kick off acetic acid. They let it sour over a few months to the level they wanted and then bottled.

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Yeah, I'm leaning toward this. It would be very interesting if there was some magic method of making Brett produce tons of acetic acid, but I'm pretty skeptical. The simple explanation would be that that there were just bugs in the barrels. I don't want to sound like I'm knocking the Surly brewers, but it almost sounds like they didn't entirely know what happened themselves. Their description of the aeration / acetic acid relationship is what really throws me.

I'm on my phone right now, but I can link you all to an article in a scientific/oenological journal that measured brett's response to oxygen. They found that as O2 went up, so did Brett's production of acetic acid, reaching rather spectacular amounts.

So, yeah, oxygenation. Probably during fermentation, too.

Interesting, I would definitely be interested in reading that. I wonder how you could oxygenate it that much without... oxidizing it. I guess aging in a barrel for a couple months could get you there. Or maybe plugging up your carboy with one of those sanitized sponge things they make for starter flasks, so oxygen could get in the whole time but contaminates couldn't.

Included are two of the many papers dealing with ascetic acid production w/r/t brettanomyces. If any of you have access to a university's library, you can get a lot of these online through relevant searches. Most deal with wine, though, as brett and beer has suffered a rather dark age lo this past century.

They avoid oxidation because the brett, unlike sacch, will continue to consume any additional O2 after it's growth phase. It just uses it to produce acetic acid rather than ethanol.

View attachment Brett Oxygen + Acetic.pdf

View attachment Brett_Ciani_Maurizio.pdf

It doesn't necessarily have to be the barrels. I've done several barrel-aged beers that had absolutely no indication of tartness from bacteria even after aging for many months.

Perhaps it could be a high percentage of acidulated malt? Brett excels in conditions of low pH, so using a grist with a healthy dose of acidulated malt is good for the brett and could also provide a perception of sourness.

moti_mo said:

It doesn't necessarily have to be the barrels. I've done several barrel-aged beers that had absolutely no indication of tartness from bacteria even after aging for many months.

Perhaps it could be a high percentage of acidulated malt? Brett excels in conditions of low pH, so using a grist with a healthy dose of acidulated malt is good for the brett and could also provide a perception of sourness.

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Yeah, I had the same thought about the acidulated malt. In May I brewed a 100% Brett (B+L) Belgian golden strong ale with around 13% acid malt to get some base sourness in there. I brewed it to be super dry too, 1.006, to really highlight the tartness. Despite all that, there's hardly a hint of Brett-funky (even after 5 months) and definitely no sourness.

My 100% brett Belgian blonde started out really clean with not much hint of brett funkiness, but now after 8 months of aging in the bottle, it has huge brett aroma and flavor - tons of pineapple brett c. I haven't brewed one with a lot of acidulated, so I don't have any data to back up my theory.