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Author Replies
04/18/08 11:18 AM  
Sounds like people want to talk about acetobacter. I'm interested in that too, especially the question of how things we "know" get translated into actual beer with an actual acetic acid taste to it. Here are some things I think we "know":

- The flavor threshold for acetic acid is ~175 ppm, and unblended beer at Rodenbach may have ~2500 ppm.

- 1 acetic acid molecule and 1 water molecule can be created from 1 ethanol and 1 O2, by acetobacter or brett.

- if you convert that reaction into masses, it turns out *1 gram of oxygen can allow for the production of ~2 grams acetic acid*. (Of course it may be that not all the oxygen gets used to produce acetic acid, so this a maximum number.)

- Going further: 1 gallon of air has 1 gram of oxygen, which again may lead to as much as 2 grams acetic acid, which in 5 gallons of beer is only 105 ppm acetic acid. To get to the taste threshhold you'd need (at least) 2 gallons of air. To get to the 2500 ppm mark you'd need (at least) 25 gallons of air. (over time)

- Raj Apte gives numbers for oxygen permeability of various fermenters, in terms of cc/L.year. You can multiply these by 2.8 to get "ppm acetic acid per year."*

- At least with the numbers Raj gives, only the HPDE bucket would get above the taste threshold in 3 years. I don't know how accurate these numbers are, of course. Different barrels in different state of repair, or with different closures, will probably vary wildly in their permeability.

I think the value in these numbers/calculations is that they at least allow some reasonable way of approximating stuff, even if they aren't perfect. The numbers suggest you can't get appreciable acetic acid in carboys or even tight barrels unless you either vent the headspace often or close then in some non-airtight way. Anyone ever have an experience that's contrary to these predictions?

(Personally I'm kind of ambivalent about acetic, so I keep stuff tight.)

Mike T
04/18/08 01:06 PM  
Re: acetobacter
Great info!

I agree that more oxygen than the math suggests must be getting into Rodenbach and La Folie. From pictures, it looks like the top of their tuns arenít touched by the beer, so they wouldnít be swelled up and airtight like the sides.

Iím not a big fan of acetic acid either, so I generally donít worry about it much. For my next round of Flanders Reds a few people will all be brewing/aging beers for an eventual group blend. My plan is to leave some of my wort after primary fermentation in a growler with aluminum foil over the top. I figure after a year it will be very vinegary and I can blend it to taste with the rest of the lactic beer. I figure once its bottled there will be no O2 and thus a stable acetic character.

04/18/08 02:14 PM  
Re: acetobacter
Makes sense to me. I think that's roughly what Raj does, to get acetic beer for blending.
04/18/08 02:31 PM  
Re: acetobacter
We've got a lambic in plastic two months now. I plan on tasting it come fall and if it's getting too acedic transfering to glass at that time. I'll keep y'all posted. : )
04/18/08 06:15 PM  
Re: acetobacter
Well, as I stated in the other thread I have my latest red in a plastic bucket, after tasting Scott R's Red during the swap. He stated his beer was aged in plastic for a year! The acetic character was minimal, and, while his was not very sour at all, it did have the closest to classic red flavor characteristics IMO. I was very impressed by the character of his beer. If it were sour, it would have been JUST like a rodenbach GC. All of my sours have been in glass, and NONE of them have any acetic character, at least not noticeable. I actually committed to using a bucket before I tried Scott's beer, because I figured it would be fun to have a funky plastic bucket to innoculate things with, but now it will also be interesting to see if I can get that slight acetic character.
05/29/08 01:13 PM  
Re: acetobacter
Due to a woefully misguided experiment with open fermentation a couple of years ago, I have several gallons of an otherwise decent pLambic that has too much acetic character (although just barely too much, in my opinion). I have been using it as a blend component for a while now, which has worked great.

I recently read, though, that it may be possible to reduce the vinegar taste: in Farmhouse Brews, Markowski mentions that brewers would add crushed eggshell to beers in order to draw off vinegar. He does not, however, go into too much detail on this point. Since I still have over five gallons of the culprit beer, I would love to reclaim it with a simple rack onto eggshells.

Does anyone know anything about this possibility? Thanks in advance.

Al B
05/29/08 01:21 PM  
Re: acetobacter
Just my opinion, but I don't think this will help greatly. Egg shell, or calcium carbonate will be needed in big amounts. The excessive CaCO3 needed may taste chalky and require blending for that reason as well.

You may experiment with CaCO3 on a small amount of brew, but I'd save the eggshells for your tomato plants :)

05/29/08 01:34 PM  
Re: acetobacter
Too bad, but thanks for the advice. It did sound too easy! I'll probably take a small amount off for a test, maybe a gallon on the shells of a dozen eggs.

05/29/08 01:35 PM  
Re: acetobacter
This is interesting...

Eggshells are 95% calcium carbonate (an alkali). They react with, and are dissolved by, acetic acid and you can make a shell-less "naked egg" by soaking an egg in vinegar.

So, you could add eggshells or calcium carbonate to your beer (you may already have food grade calcium carbonate around for brewing purposes), and it will react with the acetic acid to form water, CO2, and calcium acetate. The wikipedia page claims that ethanol and a calcium acetate solution will form a "semisolid, flammable gel":


I guess the point is that you can add eggshells or CaCO3 and react out some of the acetic acid, at the expense of creating a gel whose brewing properties are not well known to most of us. On the other hand its a traditional technique, so maybe it's not that scary.

(Eggshells also have lysosyme, I believe, which inhibits some acid-producing bacteria. But, I think that's not the point in this case.)

05/29/08 01:45 PM  
Re: acetobacter
Just saw Al's post--agree with the idea of testing on a small batch if you're going to do it at all.

Several sources give lambic as having 600-1000 mg/L acetic acid. Two acetic acid molecules (60 gm/mol) react with one calcium carbonate molecule (100 gm/mol). So, to strip 500 mg/L acetic acid out of a pure acetic/water solution, you'd need about 1.5 gm/gallon of eggshells or CaCO3.

Beer isn't a pure acetic acid solution and there's lots of crap in there that can mess things up, but that's the type of level you might need.

Al B
05/29/08 02:02 PM  
Re: acetobacter
<<ethanol and a calcium acetate solution will form a "semisolid, flammable gel": >>

- Flaming Homer?

Love that Simpson's episode: "I don't know the science of it, but fire made it gooooood".

05/29/08 02:20 PM  
Re: acetobacter
Thanks for the CaCO3 quantity recommendations, Baums, I will give it a try today.

I don't really have much to lose other than a few gallons of beer that no one would want to drink as is. If I can't drink it, maybe I can start campfires with it.

09/30/08 02:12 AM  
Re: acetobacter
So I just dug into the formerly acetic eggshell beer:

It is no longer acetic, even in the slightest. The eggshells no longer exist in their original form. This stuff actually tasted pretty good on its own, still mildly acidic but only in the most gentlemanly fashion, so I racked it onto several pounds of freshly picked cabernet sauv. grapes. Have not yet tried to ignite the remaining napalm, but that will happen in time.

Oddly enough, there is nothing that I would describe as chalky in the taste -- I did use a fairly light load of eggshells/gallon (12 eggshells/4 gallons). In fact, the flavor is far less acidic than I would have expected for a beer fermented for 3-years in direct contact with the local air, and probably far less so than it was when I added the CaCO3 -- I found the flavor and aroma objectionable then, but don't now.

Magic devinegarizer?

09/30/08 11:24 AM  
Re: acetobacter
Wow, that's very cool. And good to know it works. I'll have to try this someday
09/30/08 03:44 PM  
Re: acetobacter
10/03/08 12:21 PM  
Re: acetobacter
Just got back from Belgium, where I happened to pick up Jean-Louis Dits's book about Brasserie Vapeur. It also mentions the historical use of eggshells (or even whole eggs) that cafes would add to casks of saison after they recieved them. I love it that Mark actually did this.

BTW Jean-Louis also said that with time, a lactic-infected beer will get less sour even without eggshells. He said there were old-time brewers who would brew saison in winter not to be consumed that summer, but rather the summer of the year after (~18 months between brewing and consumption). The extra year of aging reduced the sourness.

10/04/08 09:28 AM  
Re: acetobacter
Mark did you clean the shells off first or just chuck 'em in?

Baums -

I can say from experience that what Jean-Luis speaks of, about acidity dying down over time, is true. My first sour saison from last summer was very lactic when first bottled...it was described as mouth-puckeringly acidic by the judges from the competition I entered it in (although I like that kinda sour myself). Now it's about a year and quarter old, and the last time I tried one (a month or two ago) the acidity has definitly mellowed significantly, much more balanced than when it was first bottled. I've also noticed a mellowing of acidity in my kriek that was bottled in January.

I've often read, in a homebrewing context, that things will sour more over time, but I've also read about the aging of gueze in order to tame it's sometimes overly sour profile.... I'm leaning towards the latter as opposed to the former these days.... perhaps it has something to do with the amount of CO2 dissolved in the beer from preventing it to vent off? It seems as though aging in carboys or barrels tends to increase acidity while once it is bottled the acidity eventually mellows... any thoughts?

10/06/08 10:40 AM  
Re: acetobacter
The acidity has to go up before it can go down... and that's about all I am certain of. I'm not even sure what the pathways are for brett to metabolize these acids.
10/06/08 04:26 PM  
Re: acetobacter
It sounds like acidity can diminish in barrels also. Dirty Horse from De Struise was aged 5 years and according to Urbain it was too sour earlier in it's aging. Of course 5 years is more time than most would want to wait.
11/14/08 01:35 AM  
Re: acetobacter
D'oh, missed your question, Mr. BPotts:

I boiled those puppies, then peeled the shells off, and threw them in. Disappointed in apparent lack of napalm, but pleased with de-acetification (Which, of course, could have just been from those extra 6 months in the closed fermenter).

Eric Burnley
01/18/10 02:25 PM  
Re: acetobacter
I've got a small 2-gallon bonus wort batch I played with by just adding Orval and Avery 15 (which was an all Brett beer) dregs to for fermentation. Tasted it last night and it was an abrasive vinegar to say the least. Since I'd already got the equipment out and bottles prepared, I went ahead and bottled it. Now when working with Brett from the ground up, I know to pitch in a smaller vessel, purge with CO2, and make sure to use a good airlock. It was a learning experience.

MarkO's test is so interesting to me that in the interest of SCIENCE I will go back and add a little eggshell to half the bottles to see what happens. Think it's a waste of time? That's fine. My wife and daughter like their hardboiled eggs, so shells are plentiful, and I just want to see what happens. Will report back if there is interest.

02/16/10 09:08 PM  
Re: acetobacter
I'd have to say at this point, after just having opened one of these bottles, that this experiment was a qualified success, with one down-side: there is definitely a slight boiled egg quality to this beer -- just a hint of sulfur.

Although, considering I was near to dumping it for all the vinegar, I suppose it had some degree of success. It's just not a beer for company, that's all.

02/20/10 12:46 AM  
Re: acetobacter
Doesn't Apte also say most of the acetic acid is formed in the first 1-2 weeks from enterobacter. I notice acetic/acetone aromas from the early stages of sourdough starters and sourmashes. I attribute this aroma to enterobacter or clostridium or heterfermentative lactobacillus. Enterobacter die for pH<4.2 and clostridium die for pH<4.6. Also I can't imagine a 2 week enterobacter party going on in young lambic wort without lactobacillus dropping the pH enough with lactic acid to kill off those buggers. I would also think the hopped wort would kill off enterobacter and clostridium just as effectively as it holds off lactobacillus. In any case, in my next sour mash I'm going to use a little acid malt or pure lactic acid to drop the pH to 4.1 before adding a handful of grains so I can avoid any off acetone/acetic acid aromas.
03/03/10 03:30 PM  
Re: acetobacter
Found this interesting tidbit in an old wine book. Do you think it has any merit?









page 144

Machard's Treatment. Machard says that the most successful

treatment for sour wine employed by him, is that founded

upon the affinity of vegetable substances for acids, and that he

has succeeded beyond his hopes in completely removing the acid

from a wine which was so sour that it could not be drank without

seriously disagreeing with the person drinking it. This is

his method of proceeding.

He formed a long chaplet, six feet or so in length, by cutting

carrots into short, thin pieces, and stringing them on a cord.

This he suspended in the wine through the bung for six weeks,

and at the end of the time he did not find the least trace of acetic

acid, thereby accomplishing what he had for a long time in vain

attempted. He says that this is the only treatment that succeeded

with him, and he confidently recommends it to others. But he

advises that the carrots be left in the wine at least a month and

a-half , protecting the wine from the air. And he says that there

is no danger of injuring the wine by long contact with the carrots,

or by using a large quantity of them.

03/03/10 03:31 PM  
Re: acetobacter
Oops, sorry about the formatting
03/25/10 01:24 AM  
Re: acetobacter
I just recieved my solera hungarian oak 50 liter cask.

It had red wine for a short amount of time and is

recently dumped. When I got it, I smelled the interior,

I had my wife smell it as well. Both opinions were that

it smelled like vinegar. I spoke with the source person

and was told that he thought his employee had burned a

sulfur strip inside before shipping. My question is this,

can a barrel that held red wine and then had a sulfur strip

burned inside, give the mistaken aroma of something resembling vinegar?

Of note was the irritation of the olfactory resulting

in sneezing and sniffling....sulfur di-oxide remnants?

03/25/10 10:56 AM  
Re: acetobacter
"My question is this, can a barrel that held red wine and then had a sulfur strip burned inside, give the mistaken aroma of something resembling vinegar?"

YES. I have also experienced this.

03/25/10 01:16 PM  
Re: acetobacter
"YES. I have also experienced this."

Thanks Baums I needed to hear that. but tell me, did

you use that barrel and if so, was it acetobacter?

How did the result of using that barrel flavor your end product?

03/26/10 10:09 AM  
Re: acetobacter
I used the barrel(s) to make beer, and it is good (no significant acetic acid character).

I do not know if my barrel(s) have acetobacter in them (I have not done microbial analyses) but I always assume they do. I also assume that their activity is minimized because I do not allow large amounts of oxygen into the beer.

Al B
03/26/10 09:10 PM  
Re: acetobacter
Its great seeing old posts revived.
Mike T
05/25/13 12:31 PM  
Re: acetobacter
When I do out the math I get 2.7 instead of 2.8 for the constant in the original post. Am I missing anything (haven't had chemistry since high school), or did Baums round the molar mass ratio to 2 from 1.875.

O2 = 32 g/mol

Acetic acid = 60 g/mol

It takes one molecule of O2 to produce 1 molecule of acetic acid.

60/32 = 1.875 g of acetic acid for each gram of oxygen.

1 cc of O2 weighs .00143 mg

.00143*1.875 = 2.68 mg of acetic acid

2.68 mg/l = 2.68 ppm

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