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How do you ferment your sour beers?


read 2842 times • 94 replies • posted 12/10/2013 9:19:09 AM

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OldSock
Originally posted by GarethYoung
Does anyone have good information about exactly how much acetic acid production one is likely to get from various brett strains? I remember reading something from, I think, Chad Jacobsen which gave the impression that it was difficult to get much acid at all out of brett. I think he suggested one would have to aerate the shit out of the thing for hours.


It isnít about the strain, itís about how much oxygen is let into the beer as it ferments. Aerating the starter, and the wort initially wonít give you above-threshold acetic even in a 100% Brett beer in my experience. You get acetic acid from the free-flow of oxygen for an extended period of time, say a dried out airlock (or a starter on a stir-plate, but that is diluted upon pitched).
12/12/2013 5:46:55 AM

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OldSock
Just to speak briefly to my understanding of the role of hops in sour beer.

In a spontaneously fermented beer, one of the risks is that heat-loving fast-acting Lactobacillus will sour the beer too quickly, causing problems for the wild Saccharomyces. While iso-alpha-acids are one of the primary anti-microbial compound in fresh hops, there are other less soluble compounds which contribute (oxidized beta acids etc.). This is one reason a large hopping rate and extended boil are used.

Hops are not effective at inhibiting the possibly-dangerous enteric bacteria (E. coli et al.) that can grow early on in a spontaneous fermented beer. You need pH adjustment for that.

From a microbial standpoint, when you are pitching a healthy pitch of brewerís yeast along with microbes, hops are optional. However, hops add a variety of compounds which can influence the flavor of the finished beer, even if you donít smell ďhops.Ē For example there was a Japanese study that found increased fruitiness from the aged hops compared to fresh. There are also glycosides, aromatic molecules attached to sugars which certain Brett strains can release (they are also found in fruits and spices).
12/12/2013 6:35:08 AM

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GarethYoung 1109:26
Originally posted by OldSock
Originally posted by GarethYoung
Does anyone have good information about exactly how much acetic acid production one is likely to get from various brett strains? I remember reading something from, I think, Chad Jacobsen which gave the impression that it was difficult to get much acid at all out of brett. I think he suggested one would have to aerate the shit out of the thing for hours.


It isnít about the strain, itís about how much oxygen is let into the beer as it ferments. Aerating the starter, and the wort initially wonít give you above-threshold acetic even in a 100% Brett beer in my experience. You get acetic acid from the free-flow of oxygen for an extended period of time, say a dried out airlock (or a starter on a stir-plate, but that is diluted upon pitched).


Thanks. I asked about strain since I thought it possible that different strains produce different amounts of acetic acid in the presence of the same amount of oxygen.
12/12/2013 6:54:33 AM

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CLevar 375:10
Originally posted by OldSock

It isnít about the strain, itís about how much oxygen is let into the beer as it ferments. Aerating the starter, and the wort initially wonít give you above-threshold acetic even in a 100% Brett beer in my experience. You get acetic acid from the free-flow of oxygen for an extended period of time, say a dried out airlock (or a starter on a stir-plate, but that is diluted upon pitched).




Interesting. In the 100% Brett beers that I have done, a 1400ml starter (final volume, 10mlYPGM-->100ml 1.040 wort-->1400ml 1.040 wort) that was constantly on a stirplate for the 10 days of growth contributed a "twang" to the 5 gal batch of beer it was pitched into. As the starter itself tasted and smelled of acetic acid, I presumed that this is what the "twang" could be contributed to. I no longer aerate my Brett starters (aside from intermittent "swirling" to rouse the yeast and knock CO2 out), and cold crash and decant at least 50% of the total volume, and that issue has gone away.

***Please check my maths!***

From the literature, some strains of Brett. b. have been shown to produce >10g/L acetic acid when constantly aerated, albeit in a defined medium containing glucose as the sole carbon source, and with WAAAAYYYY MORE 02 than is likely in a stirred starter (Anyone have a number for that?). It would be an interesting experiment to add the equivalent amount of acetic acid into beer, and see where that ends up flavor wise. Making WORST CASE assumptions, for the 1400ml starter, this works out to something like 0.79g of acetic into 1L of beer (I think...)? And in ppm, thatís 790 (I think...)? Pretty sure thatís above the sensory threshold.

***Please check my maths!***
12/12/2013 7:30:43 AM

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OldSock
With most things (alcoholic fermentation, lactic acid production etc.) the formulas are the same regardless of the organism. Brett makes the same number of ethanol/CO2 molecules from each sugar molecule as brewerís yeast for example. There are exceptions, for example there are two different paths for lactic acid (one which produces a molecule of ethanol and CO2 too, while the other makes an additional lactic acid molecule instead). It could be that some strains are more acetic/pH tolerant though, which could result in the eventual concentration being higher.



In terms of acetic acid flavor, saying it wasnít above threshold may have been too strong. It is certainly possible that you could get a hint of acetic under the right conditions from the starter. I know Chad has mentioned this. Iím saying in my experience it has never been enough to make a beer taste distinctly vinegary.

12/12/2013 7:46:53 AM

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BMan1113VR 7813:378
Originally posted by HornyDevil
Originally posted by BMan1113VR
Originally posted by HornyDevil
On a sort of related subject, Iím planning on doing a big sour project that involves using spent wine and spirit barrels as primary fermenters. Anybody have experience with something like this?
only at work, not at home yet.


Any advice?

Leave some head space for primary, and at home (we do not do this at work) Iíd top up after fermentation slows. Donít worry about it staying on the lees. Also use a stainless steel nail on the head to pull samples (donít take the bung off or disturb the pellicle)
12/12/2013 8:22:49 AM

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CLevar 375:10
Originally posted by OldSock
With most things (alcoholic fermentation, lactic acid production etc.) the formulas are the same regardless of the organism. Brett makes the same number of ethanol/CO2 molecules from each sugar molecule as brewerís yeast for example.



Iím pretty sure Iíve asked you this before, but have you even encountered Brett that DOESNíT make as much CO2 as expected? I ask because a brewer in the area stated that he doesnít worry about over-carbonation with Brett bottle conditioning, because in his experience, it doesnít produce much CO2.

I could see a situation in which Brett isnít JUST producing EtOH and CO2, so that some of the carbon flux goes to other products, but I didnít/donít understand how his statement could be true.
12/12/2013 8:32:12 AM

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OldSock
If Brett is producing ethanol and lowering the gravity, it is producing CO2. I have run into a couple Brett strains that are terribly un-attenuative (The Cantillon strains from Brew Science, and the De Dolle strains Iím playing with now from Yeast Bay) Ė like 10-25% AA in a standard starter wort. The fun things about them is that because they arenít munching through even maltose (it appears) let alone dextrins, they arenít super-attenuating or over-carbonating the beer. These must be strains that are prominent late in the fermentation when the malt-based fermentables are gone, and the only things left are sugars which require an enzyme other than a-glycosidase.
12/12/2013 8:44:20 AM

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HornyDevil
Originally posted by BMan1113VR
Originally posted by HornyDevil
Originally posted by BMan1113VR
Originally posted by HornyDevil
On a sort of related subject, Iím planning on doing a big sour project that involves using spent wine and spirit barrels as primary fermenters. Anybody have experience with something like this?
only at work, not at home yet.


Any advice?

Leave some head space for primary, and at home (we do not do this at work) Iíd top up after fermentation slows. Donít worry about it staying on the lees. Also use a stainless steel nail on the head to pull samples (donít take the bung off or disturb the pellicle)


Thanks for the confirmation, man. Those were all things that I had planned on doing.
12/12/2013 8:45:32 AM

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SamGamgee 2452:182
Originally posted by HornyDevil
Originally posted by BMan1113VR
Originally posted by HornyDevil
Originally posted by BMan1113VR
Originally posted by HornyDevil
On a sort of related subject, Iím planning on doing a big sour project that involves using spent wine and spirit barrels as primary fermenters. Anybody have experience with something like this?
only at work, not at home yet.


Any advice?

Leave some head space for primary, and at home (we do not do this at work) Iíd top up after fermentation slows. Donít worry about it staying on the lees. Also use a stainless steel nail on the head to pull samples (donít take the bung off or disturb the pellicle)


Thanks for the confirmation, man. Those were all things that I had planned on doing.


While Iíve never done sour barrel fermentation, only clean ale, I would add that you will probably want a blowoff for primary, which can be a 1/2in tube into a bung with the same sized hole, then just put the end in a bucket next to the barrel. We do barrel fermentation with a moderate top-cropper and see large amounts of krausen out of the blowoffs in most cases. If you just put an airlock on top, youíd get a world of mess.
12/12/2013 10:29:11 AM

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