Sour Beers - Remaining Questions

[Oldsock]

So after three and a half years of research, writing, and editing, American Sour Beers is finished!... sort of. Despite my best efforts there were a few questions I was unable to answer satisfactorily. u/hirschb suggested I start a thread about them. So maybe you can help me answer my questions, and I can try to help answer any questions you might have that weren't covered in the book!

Hopefully they'll be a second edition down the line, never too early to start noting areas for improvement! I also posted an errata page, just a few typos and location errors so far (not bad for 400 pages).

My 5 lingering questions:

1. Why does Brett seem to produce more of it's funky character during bottle conditioning than in a fermentor? Is the pressure preventing volatile phenols from escaping? Does the CO2 pressure alter the biological pathways? Does the dissolved CO2 itself (carbonic acid) play a role? Someone came up to me at NHC and noted that their sours seem to have gotten less funky after moving from sea level to 10,000 ft.

2. What factors determine how much lactic acid Lactobacillus produces (in addition to adequate fermentable carbohydrates). It seems like the results with some strains are wildly different. I've never had luck with White Labs L. delbrueckii (even without competition), but it sounds like some people have used it to produce very tart beers.

3. What exactly causes poor head retention is sour beer. The low pH? Protein degradation by microbes? Low hopping rate? (I suspect the answer is a combination of these things, depending on the method).

4. Why do barrel-aged beer tend to taste more lactic than sour beer fermented in impermeable fermentors? Is it sub-threshold acetic acid boosting the overall perception of acidity? Or is there really more lactic acid produced thanks to micro-oxygenation or another factor.

5. Why do sour mashes exposed to the air often become butyric (vomit-rancid butter)? As far as I've read the butyric acid production is always anaerobic.

Citations preferred over conjecture when answering.

 

[ChefRex]

No answers for you but want to follow along, My first sour is chugging along in the cellar and I will have a copy of the book in my hands on Tuesday, looking forward to it.
Thanks for writing it!

 

[strambo]

Thanks for starting this thread, I just ordered your book and will no doubt have questions. The sours from Cascade are my inspiration for trying my own, my wife really likes them.


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[metic]

I can't find the page in the book where you discuss this, but one thing I'd like to understand better is why some people find a difference in the perceived character of the acidity produced by pediococcus and lactobacillus. I think you say in the book (annoying that I can't find the page) that the acid itself is the same, so any difference must have to do with other fermentation byproducts. I'm curious about what is going on here.

 

[hotspurdotus]

Good thread!

About #2. My experimental brewing crew started a Berliner Weisse project. We did a large batch, and split it into several fermenters where we pitched different strains of Lacto, including homemade and WLP677, at high temps. We were able to produce a tart, bready beer with both homeade lacto and WLP677 when we fermented in purged cornie kegs and pitched Brett Brux a week later. The same pitch schedule in Better Bottles produced a much less tart product.

We are on the third generation of our Lacto/Brett strains. We're fermenting in purged cornies and producing very tart Berliners in just a few days. 2 of our strains, a homemade and 677 strain, taste virtually identical.

Is it the O2 free environment? Does the Brett make the magic happen? A combo of the 2? We're still trying to discover the key, but it's been a rewarding experiment; nothing like a crisp tart Berliner to cut through this muggy weather!

 

[Oldsock]

I can't find the page in the book where you discuss this, but one thing I'd like to understand better is why some people find a difference in the perceived character of the acidity produced by pediococcus and lactobacillus. I think you say in the book (annoying that I can't find the page) that the acid itself is the same, so any difference must have to do with other fermentation byproducts. I'm curious about what is going on here.

One avenue I investigated is that there are two different "handed" lactic acid molecules D/L and R/S (mirror images - like glucose and dextrose), but my understanding is that the human tongue can't distinguish them. Couldn't find a good citation (which is why I didn't write about it), but per my PhD cancer researcher friend.

My best guess is that beers with Pedio tend to be aged longer and barrel aged, and likely have some acetic acid. Tied up with my #4.

 

[Borgstrom]

I brewed a RR consecration clone about 1.5 years ago, added oak chips about 2 months ago, and bottled about 2 weeks ago. It tasted fantastic before the oak, great but a little too oaky after the oak chips (4 weeks on oak would have been better than 6 weeks I think). Sampled a bottle last week and it was not good at all -- no carbonation, some new off-flavors that weren't there before.

Then American Sours came in the mail, and I realized that there was likely very little viable yeast after 1.5 years in secondary and that I should have re-yeasted during bottling. Doh!

How can I recover? Current thinking is to keep bottles at room temperature for another 1-2 months, inverting periodically, and hope for the best? Alternative might be to empty all bottles into vessel, re-pitch yeast, re-bottle. Sounds kind of scary, with risk of oxidation, contamination, etc. The beer was so good, and we had waited so long...I don't want to lose this batch! Any suggestions?

 

[Oldsock]

I think that is a great place to start. Likely there is viable Brett in there. If you have some, but not enough carbonation in a couple months, keep it up. If you don't have any carbonation by then, open, dose with rehydrated wine yeast (a dropper would help), and re-cap. The fact that the flavor has changed likely means Brett is getting going. Good luck!

 

[ColoHox]

So after three and a half years of research, writing, and editing, American Sour Beers is finished!... sort of. Despite my best efforts there were a few questions I was unable to answer satisfactorily. u/hirschb suggested I start a thread about them. So maybe you can help me answer my questions, and I can try to help answer any questions you might have that weren't covered in the book!

Hopefully they'll be a second edition down the line, never too early to start noting areas for improvement! I also posted an errata page, just a few typos and location errors so far (not bad for 400 pages).

My 5 lingering questions:

1. Why does Brett seem to produce more of it's funky character during bottle conditioning than in a fermentor? Is the pressure preventing volatile phenols from escaping? Does the CO2 pressure alter the biological pathways? Does the dissolved CO2 itself (carbonic acid) play a role? Someone came up to me at NHC and noted that their sours seem to have gotten less funky after moving from sea level to 10,000 ft.

2. What factors determine how much lactic acid Lactobacillus produces (in addition to adequate fermentable carbohydrates). It seems like the results with some strains are wildly different. I've never had luck with White Labs L. delbrueckii (even without competition), but it sounds like some people have used it to produce very tart beers.

3. What exactly causes poor head retention is sour beer. The low pH? Protein degradation by microbes? Low hopping rate? (I suspect the answer is a combination of these things, depending on the method).

4. Why do barrel-aged beer tend to taste more lactic than sour beer fermented in impermeable fermentors? Is it sub-threshold acetic acid boosting the overall perception of acidity? Or is there really more lactic acid produced thanks to micro-oxygenation or another factor.

5. Why do sour mashes exposed to the air often become butyric (vomit-rancid butter)? As far as I've read the butyric acid production is always anaerobic.

Citations preferred over conjecture when answering.

I'll throw in my research (with citations). I have a PhD in bacterial physiology, so most of this is from a scientific perspective, as opposed to a beer perspective.

I can't comment specifically on #1 or 4, but the answers may be mixed in as part of the answers to other questions.

As for #2, the results are so variable because the species of LAB are wildly different. As expected, temperature, sugar composition, pH, cell density, oxygenation all play a role in the final production of acid from the LAB, with pH and oxygenation having the most impact. Even species which are classically homofermenters produce mixed acid (formate, acetate) depending on the sugars available, or at increased temperatures and/or pH. For example, L. delbrueckii produces lactic acid more efficiently when using glucose and fructose simultaneously compared to glucose alone. Additionally, L. helveticus is more efficient using maltose compared to glucose. The impact of oxygenation during souring is seen by comparing the growth rate to acid production. Lactic acid production is associated with cell growth. During aerobic fermentation, the cell yield is higher compared to anaerobic fermentation, but the growth rate is lower. Cell growth rate and lactic acid production is ~2.3 times higher in anaerobic fermentations. Thus, the end-products of sugar metabolism and the range of sugar substrates which can be used by the LAB depends on the oxygenation of the culture. In fact, the aerobic production of acetate, rather than lactate, generates more ATP. During long incubations in the presence of oxygen, such as in a barrel, metabolically active LAB convert lactate to acetate. This process does not occur when oxygen is not available. I don't know how this would affect perceived sourness, or actual sourness for that matter. So maybe the TL;DR for this is that the end result of souring a beer is dependent on a variety of factors, most of which are easily controlled. However, if these variables are not managed the end result can be completely different between batches. Condon et al, FEMS Microb Revs. 1987. Fu et al. Biochem Eng J. 1999. Hofvendahl et al. Enz and Microb Tech. 2000. John et al. Appl Microbiol Biotechnol 2007.

#3: Lactic acid bacteria are well known for their limited ability to synthesize amino acids and depend on preformed amino acids in the growth media as a nitrogen source. While the capacity to degrade peptides differs among species of LAB (mechanisms in some species are inferred from genome sequence and not proven enzymatically), the proteolytic capacity of most LAB is well understood. Thus, the microbes involved in souring a beer are utilizing the proteins involved in head retention for continued metabolism. Kunji et al. Kluwer Acad. 1996; Savijoki et al Appl Microbiol Biotechnol. 2006.

#5: A sour mash is truly a microbial ecosystem. Within this ecosystem there are zones of aerobic and anaerobic commensal microbial activity. This feature is common in other mixed microbe populations. Temperature, pH, oxygen level, and nutrient availability determine the composition of microbes able to participate in these environments. Vissers et al. J. Dairy Sci 2007.

These are clearly very complicated processes, and it is very difficult to edit things down. I really enjoy your blog and am excited to read this book. Also, with institutional access, I can pretty much find any paper, so let me know if you want/need anything specific.

Also, HBT is not letting me upload the PDFs for these references, something about dimensions? Please PM me if you want and I can email them to you.

 

[smokinghole]

Its nice to see my suspicions pretty much confirmed above about a few things ive had hunches about.

For #3 In addition to no foam retention ive found that my mixed culture brews end up crystal clear like they were filtered even with only long term cellar storage. Other beers with pure cultures and even pure culture brett secondary stay hazy for a long time. Once I started getting more Brett diversity from say an Orval bottle (im told at least six distinct colonies can be picked out of a properly diluted sample on a plate) and especially a wild mix of lambic bottle yeasts/ bacteria my never chilled beers were pouring clears as a Prima Pils.

 

[ColoHox]

Coflocculation of mixed culture batches is a well known occurrence. A highly flocculent strain of either yeast or bacteria can pull out a less flocculent strain.
From Sosa 2008, Peng 2001 and here:
http://onlinelibrary.wiley.com/doi/10.1111/j.1567-1364.2009.00579.x/full

Graham Stewart as done a bunch of work on this phenomenon.

 

[FredTheNuke]

Hah! More proof for my SWMBO that us home brewers aren't all broke college kids... PhDs and all...


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[Qhrumphf]

Hah! More proof for my SWMBO that us home brewers aren't all broke college kids... PhDs and all...


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Fortunately y'all aren't all broke college dropouts...

Subscribed. I've always noticed and wondered about the head retention thing. I simply assumed it was wild yeast and bacteria eating various compounds that helped with foam stabilization.

Although I've noticed that commercial sours seem to have slightly better (albeit not by much) retention than mine. My sours usually have nearly zero retention, and never known why. Retention on my non-sours is just fine.

 

[gandelf]

1. Why does Brett seem to produce more of it's funky character during bottle conditioning than in a fermentor? Is the pressure preventing volatile phenols from escaping? Does the CO2 pressure alter the biological pathways? Does the dissolved CO2 itself (carbonic acid) play a role? Someone came up to me at NHC and noted that their sours seem to have gotten less funky after moving from sea level to 10,000 ft.

First, I don't have citations. But I do have around 11 years of Brett, all Brett and sour experience. Second, I'm not a big funk head. That being said, I have found pressure (stress) to be a very effective means to manipulate (increase) the level of funk. I brewed a 1 gallon all brett and fermented it closed for one month; it had a significant level of funk. As a result, I built a spunding valve for fermentation to experiment with. This has worked well for me. I now ferment in Speidel fermenters, this allows me to sample without opening the fermenter. My standard routine now is to sample periodically and if I feel it needs more funk? I apply some/more pressure.

I have found in life when pressure is increased; i.e. society, people, wife and etc.. The result will be increased funk.

Note: It's very important to utilize a fermenter with enough head space to ensure krausen can't foul the spunding valve.

 

[smokinghole]

Coflocculation of mixed culture batches is a well known occurrence. A highly flocculent strain of either yeast or bacteria can pull out a less flocculent strain.
From Sosa 2008, Peng 2001 and here:
http://onlinelibrary.wiley.com/doi/10.1111/j.1567-1364.2009.00579.x/full

Graham Stewart as done a bunch of work on this phenomenon.

My post was more in reference to protein induced haze. That is equally interesting though. I have a brett old ale from 2011 that is still has chill.haze for the bottles that only spent time at cellar temps. Then I have mixed culture beers from last year that pour with out any haze even though they spent no time at fridge temps except just before serving. I always suspected.the clarity and lack of foam was directly related to protein metabolism by the mixed culture.

 

[Warthaug]

Colohox and I share a similar background, and he beat me to most of the answers. None-the-less...

1. Why does Brett seem to produce more of it's funky character during bottle conditioning than in a fermentor? Is the pressure preventing volatile phenols from escaping? Does the CO2 pressure alter the biological pathways? Does the dissolved CO2 itself (carbonic acid) play a role? Someone came up to me at NHC and noted that their sours seem to have gotten less funky after moving from sea level to 10,000 ft.

Phenol (funk) production has been heavily studied in the wine industry, in both brett and sacc. The answer to your question is two-fold; firstly, the genes involved in phenol formation are upregulated during anaerobic fermentation. Meaning they don't have a significant impact until later in fermentation (once all O2 is consumed) and then into ageing and bottling.

Secondly, at least in brett, the highest rates of phenol synthesis are observed in non-dividing yeast. Again, this is something that happens late in the fermentation process, especially in the high-alcohol, low-O2, nutrient depleted environment of the bottle.

Two quick refs, but they just scratch the surface:
http://onlinelibrary.wiley.com/doi/10.1002/jsfa.2740620213/abstract
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2009.04561.x/abstract

2. What factors determine how much lactic acid Lactobacillus produces (in addition to adequate fermentable carbohydrates). It seems like the results with some strains are wildly different. I've never had luck with White Labs L. delbrueckii (even without competition), but it sounds like some people have used it to produce very tart beers.

This was excellently answered by Colohox. The genetic differences between strains of lacto are enormous; you cannot think of one species of laco as equivalent to another.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015964
http://www.biomedcentral.com/1471-2164/13/533

5. Why do sour mashes exposed to the air often become butyric (vomit-rancid butter)? As far as I've read the butyric acid production is always anaerobic.

Buteric acid is not the only compound that produces enteric flavours and aromas. Many enteric bacteria form aromatic amino compounds during amino acid degradation which produce enteric aromas & flavours.

As for buteric acid, it can be produced by anaerobic fermentation (anaerobic), but some of the producing organisms are somewhat aerotolerant. In addition to buteric fermentation, buteric acid can also be produced by some lipid catabolism pathways.

Plus, as most people conduct them, sour mashes are relatively anareobic; I'd suspect that rather than "becoming" buteric, air exposure wither provides colonization with buterate-producing organisms, or simply volatilizes beuteric acid already present in the mash.

Bryan

 

[Oldsock]

Thanks for all the responses so far!

The impact of oxygenation during souring is seen by comparing the growth rate to acid production. Lactic acid production is associated with cell growth. During aerobic fermentation, the cell yield is higher compared to anaerobic fermentation, but the growth rate is lower. Cell growth rate and lactic acid production is ~2.3 times higher in anaerobic fermentations. Thus, the end-products of sugar metabolism and the range of sugar substrates which can be used by the LAB depends on the oxygenation of the culture. In fact, the aerobic production of acetate, rather than lactate, generates more ATP.

So could pitching yeast in addition to Lacto be beneficial for lactic acid production (as the yeast would quickly use any available oxygen), or would the Lacto run through the O2 quickly on its own and switch to lactic acid production as long as no additional air was allowed to contact the wort/beer?

#3: Lactic acid bacteria are well known for their limited ability to synthesize amino acids and depend on preformed amino acids in the growth media as a nitrogen source. While the capacity to degrade peptides differs among species of LAB (mechanisms in some species are inferred from genome sequence and not proven enzymatically), the proteolytic capacity of most LAB is well understood. Thus, the microbes involved in souring a beer are utilizing the proteins involved in head retention for continued metabolism. Kunji et al. Kluwer Acad. 1996; Savijoki et al Appl Microbiol Biotechnol. 2006.

I included a bit about this in the book as well. Seems like a good reason to add high protein adjuncts and/or chit malt. I’d also read that lowering the pH in advance to ~4.4 can help to inhibit proteolytic enzymes produced by Lacto.

pressure (stress).

While I agree that pressure increases Brett character, I’m not convinced that “stress” is the mechanism behind it.

Again, this is something that happens late in the fermentation process, especially in the high-alcohol, low-O2, nutrient depleted environment of the bottle.

Very interesting, and certainly helps to explain the differences between 100% Brett fermentations and mixed-fermentations. However, none of the conditions you describe are specific to the bottle. If anything bottling would introduce a small amount of oxygen compared to sitting in a secondary fermentor. It seems like something in addition to low oxygen/nutrient is going on in my experience. Anecdotally, bottling a young beer with Brett pitched at bottling seems to produce “Brett” character more rapidly than taking the same beer and pitching Brett into a secondary fermentor with an airlock.

The genetic differences between strains of lacto are enormous; you cannot think of one species of laco as equivalent to another.

That is certainly a well explored area. What I was asking was why two brewers using the same species/strain of Lacto sourced from the same supplier seem to get such different results. My understanding is that White Lab’s Lactobacillus delbrueckii (for example) is heterofermentative. That means for ever sugar it ferments it should produce one molecule each ethanol, CO2, and lactic acid (along with a smattering of other byproducts). What I don’t get is how I can pitch a starter of L. delbrueckii and nothing else, see plenty of CO2 production and a large gravity reduction, yet taste essentially no lactic acidity. Conversely, other brewers have told me that they have made satisfactorily sour beers with the same culture and no additional souring microbes.

 

[ColoHox]

So could pitching yeast in addition to Lacto be beneficial for lactic acid production (as the yeast would quickly use any available oxygen), or would the Lacto run through the O2 quickly on its own and switch to lactic acid production as long as no additional air was allowed to contact the wort/beer?

I think the competition between the two organisms would not be beneficial, or it might contain subtle contributions from both organisms. If the sour character is intended to be more apparent, the preferred route would be to first pitch LAB in a very still (degassed or as little aeration as possible) wort for lactic acid production, then pitch a yeast for ethanol production.

That is certainly a well explored area. What I was asking was why two brewers using the same species/strain of Lacto sourced from the same supplier seem to get such different results. My understanding is that White Lab’s Lactobacillus delbrueckii (for example) is heterofermentative. That means for ever sugar it ferments it should produce one molecule each ethanol, CO2, and lactic acid (along with a smattering of other byproducts). What I don’t get is how I can pitch a starter of L. delbrueckii and nothing else, see plenty of CO2 production and a large gravity reduction, yet taste essentially no lactic acidity. Conversely, other brewers have told me that they have made satisfactorily sour beers with the same culture and no additional souring microbes.

L. delbrueckii is a homofermenter. However, as I pointed out earlier, the culture (wort) conditions must be suited to this species for it to perform correctly. The homofermenters will use alternate physiological processes depending on the conditions, eg. glucose limitation, increased pH, decreased temperature, oxygen, specifically. While the L. delbrueckii is still using the homofermentative pathway during growth in these conditions, pathway intermediates are shuttled differently. When oxygen is present, a critical enzyme in the lactate pathway is deactivated, instead resulting in the production of CO2, acetyl-CoA, and electron carriers...and probably explaining why you get little, if any, sourness from these batches.

 

[Warthaug]

That is certainly a well explored area. What I was asking was why two brewers using the same species/strain of Lacto sourced from the same supplier seem to get such different results. My understanding is that White Lab’s Lactobacillus delbrueckii (for example) is heterofermentative. That means for ever sugar it ferments it should produce one molecule each ethanol, CO2, and lactic acid (along with a smattering of other byproducts).

That isn't exactly correct. Heterofermentative lacto have the biochemical machinery for both ethanol and lactic acid production, but it doesn't mean they'll produce the two in a 1:1 ratio (indeed, under food-fermenting conditions, the ratio is generally 2:1 lactate:ethanol). Rather, the two pathways exist independently of each other, each "competing" for the pool of pyruvate being produced by glycolysis. The rates of production of ethanol vs. lactate depends on a number of different things:

1. Relative expression levels of the alcohol vs. lactate producing proteins. More of one pathways protein generally results in higher rates of production of that pathways products
2. Reaction rate. Even assuming equal amounts of lactic vs ethanolic fementating enzymes, they will not function at the same speed. Moreover, reaction rates don't scale linearly with temperature, so alterations in fermentation temperature can alter the ratio of lactate versus ethanol without changes in protein expression levels. In addition, pH can have a big impact on reaction rates
3. Concentration of products. Increasing concentration of products will slow the biosynthesis of that product, which can lead to more biosynthesis being "shunted" through other pathways. This isn't always intuitive - for example, high CO2 levels produced by other organisms in the mash can reduce the rate of ethanol production.

Sorry, no references for that. Enzymatic rates and how they're impacted by reactant and product concentrations, temperature, etc can be found in most intro biochemistry texts.

EDIT: the 2:1 ratio of lactate:EtOH comes from an undergrad lab I run when we ferment cabbage. It may not hold true for all lactobacilli

What I don’t get is how I can pitch a starter of L. delbrueckii and nothing else, see plenty of CO2 production and a large gravity reduction, yet taste essentially no lactic acidity. Conversely, other brewers have told me that they have made satisfactorily sour beers with the same culture and no additional souring microbes.

Without some pretty intensive (and expensive) experimentation it would be hard to say with certainty, but I'd guess that differences in pitch rate, temperatures, nutrient availability, etc, are leading to expression changes in the lactate dehydrogenase versus pyruvate decarboxylase + alcohol dehydrogenase enzymes, leading to differences in production of lactate versus ethanol.

That said, and as I'm sure you're aware, much of taste is relative. It may not be that total lactate is different, but rather that the perception of it is different due to differences in recipe formulation and whatnot.

Bryan

 

[Warthaug]

Arrg, that's embarrassing! I totally mixed up the pathway leading to ethanol in lacto! It splits off way before pyruvate, so all the enzyme names I gave you on the ethanol side are wrong. . None-the-less the concept is the same. Both ethanol & lactate share a substrate, & the various factors I mentioned all impact on how much"flow" there is through the two pathways.

Bryan (with pie on my face)

 

[Weezy]

Just another novice offering his opinion:



1. Brett more funk from bottles than fermenters?

Oxygen availability? Brett ferments faster in the presence of oxygen but is funkier w/o.
Time? Brett only or Sacc & Brett or Sacc, Brett, & Bugs? The question seems to unspecific with regards to the other important factors? How much time did the Brett have to work prior to tasting? Depending on conditions, there may not be much Brett character for 6-8 months? Based on other info, there appears to be synergy between Brett and bugs, where either may be producing acids and/or esters depending on oxygen availability, pH, temperature at any given time during a long term secondary fermentation.

2. Lacto performance?

Very pH dependent and acid sensitive aren’t they? They seem to prefer of 5 pH, churn out a lot of lactic acid and ethanol, quickly dropping the pH to below 4 and killing a lot of themselves in the process?

When pitched? Lacto may prefer simple sugars. If pitched in the primary, when pH is ideal and acid density is low, it should be happier and work harder for longer. Pedio and Brett seem to have a better synergy and Pedio is more survivable, for better long term performance.

3. Poor head?

Viscosity...Lactic acid is known to reduce viscosity. I am looking forward to reading Mr. Bamforth’s Foam book.

4. Barrel vs. stainless and the former being more lactic?

Frank Boon said his best Lambic comes from his large Foudres…not barrels, not SS or plastic tanks. This isn’t to mean the most lactic beer, but certainly the most complex and pleasing. This is a very big grey area that attracts my novice attention quite a bit as I try to choose ferm vessels. One factor absolutely has to be additional carbohydrates available. Oxygen is something I don’t fully understand with regards to the fine line between beneficial levels for the Brett and bacteria vs. oxidation; similarly how glass carboys with various semi-porous caps permit some oxygen infusion…through the pellicle? I’m planning to build a mach-Foudres for small batch, long term Lambic fermentation, using a combination of stainless and oak (i.e. white oak exposed to air and beer) to mimick Foudres level of oak exposure.

Perhaps other various, rogue bacteria (Pedio as well?) in the oak, even at low concentrations, contribute…more than we might think?

5. Enterobacter?

I think this is inevitable and sees a diminished significance in professional brewing due to the shear volume of un-tainted wort vs. the near surface wort that is impacted.

 

[Warthaug]

Sorry, missed this when replying.

Very interesting, and certainly helps to explain the differences between 100% Brett fermentations and mixed-fermentations. However, none of the conditions you describe are specific to the bottle.

But neither is phenol production. The genes for phenol production will get upregulated as the wort become anoxic, and will be further unrelated as the Brett becomes non-dividing. Meaning phenol production should begin in the fermenter, and get every stronger as conditions get more and more phenol "friendly".

If anything bottling would introduce a small amount of oxygen compared to sitting in a secondary fermentor

But (depending on the closure) O2 entry into the bottle is a 1-time event, while even a glass carboy will have a slow o2 influx around the bung.

Anecdotally, bottling a young beer with Brett pitched at bottling seems to produce “Brett” character more rapidly than taking the same beer and pitching Brett into a secondary fermentor with an airlock.

Which would be in-line with O2 flux rates of Carboys related to bottles.

Bryan

 

[Arrheinous]

For #1: Saccharomyces can make esters but can't break them. Brett can both make esters and break them apart again; the more building blocks you have in there (pitching post-primary), the more flavor contributions Brett can make over time. If you pitch early the Brett will ferment rather clean.

 

[dantheman13]

The impact of oxygenation during souring is seen by comparing the growth rate to acid production. Lactic acid production is associated with cell growth. During aerobic fermentation, the cell yield is higher compared to anaerobic fermentation, but the growth rate is lower. Cell growth rate and lactic acid production is ~2.3 times higher in anaerobic fermentations. Thus, the end-products of sugar metabolism and the range of sugar substrates which can be used by the LAB depends on the oxygenation of the culture.

This bit of information caught my eye, and I was wondering if it could account for Mike T.'s experience with not getting a lot of lactic acid production from Wyeast/WL Lactobacillus? I believe that he tends to make a big starter with his Lacto, where as I have had great success getting a lot of lactic acid in a Berliner by just pitching a vial of WLP677 L. delbrueckii into non-aerated wort for 7 days at 85-95F before pitching Saccharomyces. Just a thought!

 

[trentm]

1. Why does Brett seem to produce more of it's funky character during bottle conditioning than in a fermentor? Is the pressure preventing volatile phenols from escaping? Does the CO2 pressure alter the biological pathways? Does the dissolved CO2 itself (carbonic acid) play a role? Someone came up to me at NHC and noted that their sours seem to have gotten less funky after moving from sea level to 10,000 ft.

Thanks for the book! It's a wealth of information on a complex and little understood subject. While I can't answer the question above, I have made an observation that may stimulate some more qualified people to look into the possibilities of reasons for the apparent differences in Brett fermentations.

Recently, I successfully isolated a pure culture of the Brettanomyces found in Orval. Two methods were used to confirm the isolation and purity of the isolate, microscopic and trial fermentation. Since I had little knowledge of the physical characteristics of the genus, I used an isolate of WLP650 (Brett b) and a Sacc isolate from my library for comparison. The first microscopic observation of the putative Brett isolate was from a wort agar plate and lead me to believe the attempt was unsuccessful because I could see two distinct cell morphologies. Comparing these to the Sacc isolate, one cell type was very similar, i.e. almost round and nearly twice the size of the other cell type which was not only smaller but oval (football shaped). The ratio was about 1:3 large to small. However, the WLP650 isolate (grown in the same conditions) had similar cell morphologies with both cell types present. Could my WLP650 isolate be contaminated with Sacc? I decided to proceed with a trial fermentation. To my pleasure, the putative Brett culture took 3 days before visible fermentation began while the Sacc culture was in full growth stage after 12 hours. The WLP650 culture was faster than the Orval Brett culture but slower than the Sacc culture. Microscopic observation of the putative Orval Brett culture relieved the presence of both the original cell morphologies and a third! However, the large, oval cells were at a much lower ratio compared to the agar plate produced cells at about 1:10. Interestingly the third cell type did not appear yeast like at all but more like fat fungal hypha. However, these were rare compared to small football shaped cells at about 1:100. The culture was stepped up to 250ml and allowed to complete the fermentation, taking three weeks. The aroma and taste of the culture is typical of Brettanomyces. I have conclude the isolation was successful and the cellular physical phenotype of this isolate of Brettanomyces is influenced by its environment.

So my hypothesis is: If the culture environment can influence cellar morphology, the physical phenotype may also influence it's biochemical properties.

 

[MileHighBrewer]

This bit of information caught my eye, and I was wondering if it could account for Mike T.'s experience with not getting a lot of lactic acid production from Wyeast/WL Lactobacillus? I believe that he tends to make a big starter with his Lacto, where as I have had great success getting a lot of lactic acid in a Berliner by just pitching a vial of WLP677 L. delbrueckii into non-aerated wort for 7 days at 85-95F before pitching Saccharomyces. Just a thought!

Dan, I had the same result by massively under pitching a brett culture at the same time as fresh lacto (tyb with 1.068 so around 200k/ml) the lacto got one helluva head start and made a very tart, tangy, sour beer very young. The brett and sacch went to work in about 3-4'days finally making a krausen. I'm going to do this again soon by pitching like you describe. It's these little findings by homebrewer accident that can change how the game is played!