[CB-Illinois]

Hi all,

I have noticed in my extract beers something that I would describe as slightly acidic after cask conditioning.  Is that along the same lines as the extract beer "twang"?  I kind of dought it because bannana and caramal seem to be the descripters people in this forum are using. 

Has anyone heard of acid being produced by yeast during bottle/keg conditioning?  The man running the homebrew supply shop said that happens and I should no longer bottle/keg condition.

As always, thanks for the feedback!

[saintpierre]

My first thought that it is a sanitation issue...
Can you describe acidic a little more.  Aroma, flavor, etc. is generic terms such as vinegar-y...

[CB-Illinois]

The beer smells great, but tastes a little vinagar-y...

[Jimmy K]

Vinegar-y smell/flavor probably comes from acetobacter (contaminating bacteria), which creates acetic acid. Yeast really don't produce acetic acid, even when they are abused. Bottle/keg conditioning definately has nothing to do with it.

[nateo]

The man running the homebrew supply shop said that happens and I should no longer bottle/keg condition.

Are you sure you heard him correctly? That might be (some of) the worst homebrew store advice I've ever heard.

Acetobacter is really common. It's on probably everything you touch. If it gets into your beer it will make vinegar. I agree with the others that it's likely a contamination issue.

[morticaixavier]

The man running the homebrew supply shop said that happens and I should no longer bottle/keg condition.

Are you sure you heard him correctly? That might be (some of) the worst homebrew store advice I've ever heard.

Acetobacter is really common. It's on probably everything you touch. If it gets into your beer it will make vinegar. I agree with the others that it's likely a contamination issue.

yeah it sounds like infection. I like that advice though. so if you are not supposed to keg or bottle condition are you supposed to just drink the flat beer out of the fermenter?

By the By, keg/bottle and cask conditioning are different animals. cask is very specific to the equipment.

[CB-Illinois]

Hi all,

Thank you for the advice on what this is, and that the homebrew store gu was wrong.  I kind of thought so...he recommended not bottle/keg conditioning and buying CO2 tanks and a regulator from him.  That sounded like he was just trying to make a sale...

Thanks for the advice!

[Jimmy K]

Acetobacter is aerobic - it often isn't much of a problem if you're kegging/bottle conditioning because there is no oxygen. But if you're cask conditioning and using ambient air to fill the headspace in the cask, then there will be plenty of oxygen in there (and you're probably innoculating with acetobacter too).

[morticaixavier]

Hi all,

Thank you for the advice on what this is, and that the homebrew store gu was wrong.  I kind of thought so...he recommended not bottle/keg conditioning and buying CO2 tanks and a regulator from him.  That sounded like he was just trying to make a sale...

Thanks for the advice!

ahh okay, that makes a little more sense. If you are kegging don't you already have a regulator co2 bottle? youc an naturally carbonate with priming sugar in the keg but you do still need co2 to push the beer out. If you are pushing using air/gravity like a cask conditioned ale then it will eventually spoil on you. some acetobacter is unavoidable if you are continuously pulling ambient air into the keg. and the presence of the air speeds up the aceto action. so he may actually be right. bottling on the other hand... well if your sanitation is good there should not be a problem there. if you are repeatedly getting this off flavour in your bottled brew you might want to think about replacing all the plastic, rubber, and other non-glass, non-metal items all the rubber gaskets and o-rings are potential vectors in the kegging system and all the plastic tubing, fermenters, and beer lines are vectors everywhere else.

[anje]

Acetobacter is aerobic - it often isn't much of a problem if you're kegging/bottle conditioning because there is no oxygen. But if you're cask conditioning and using ambient air to fill the headspace in the cask, then there will be plenty of oxygen in there (and you're probably innoculating with acetobacter too).

Lactobacilli might be a problem, though, if they get in. 

[tschmidlin]

Yeast really don't produce acetic acid, even when they are abused. Bottle/keg conditioning definately has nothing to do with it.

Yeast produce acetic acid, it is just that it is usually not detectable in the flavor as such.  The presence of acetic acid is the primary cause of chronological aging and cell death in long term yeast storage.

I agree though, that this is some strange advice.  Plenty of places bottle/keg condition without getting off flavors, so clearly that's not it.  I think you need to be extra diligent about your cleaning/sanitizing regimen for a while and see if that makes a difference.

[thomasbarnes]

Yeast produce acetic acid, it is just that it is usually not detectable in the flavor as such.  The presence of acetic acid is the primary cause of chronological aging and cell death in long term yeast storage.

To clarify, even unhealthy yeast don't produce acetic acid at noticeable levels, in the same way that an acetobacter infection would produce.

Unless you've got a lot of air contact with your beer and you're leaving your beer for long periods of time, I'm not sure that you've actually got an acetobacter infection.

"Cidery" notes can be produced by yeast. Ethyl acetate is one of the most common esters in beer and it smells like ripe apples, while acetaldehyde smells like unripe/green apples. Both are byproducts of fermentation. At low levels, "cidery" notes can be confused with apple cider "vinegary" notes.

The way to determine if you're got acetobacter infection (true "vinegary" notes) vs. just "cidery" notes is to bottle some of your beer and let it age. If the "vinegar" notes get stronger with aging, the beer's body goes down and the carbonation level goes up, you've actually got an infection. If the "vinegar" notes dissipate with age, it's probably just normal fermentation byproducts.

If you actually have an acetobacter infection, other folks have given you good advice on sanitation and excluding O2.

If you have acetaldehyde and/or estery notes, that's more likely to be a problem with "yeast management." Quick fixes are to pitch more yeast and to aerate your wort just after pitching your yeast (vigorously stirring or rocking your wort for about 10 minutes is the low-tech version of how to solve this problem).

[Jimmy K]

The way to determine if you're got acetobacter infection (true "vinegary" notes) vs. just "cidery" notes is to bottle some of your beer and let it age. If the "vinegar" notes get stronger with aging, the beer's body goes down and the carbonation level goes up, you've actually got an infection. If the "vinegar" notes dissipate with age, it's probably just normal fermentation byproducts.

I've got a question about this - wouldn't acetobacter likely cease activity after bottling since O2 is now excluded?

[tschmidlin]

The way to determine if you're got acetobacter infection (true "vinegary" notes) vs. just "cidery" notes is to bottle some of your beer and let it age. If the "vinegar" notes get stronger with aging, the beer's body goes down and the carbonation level goes up, you've actually got an infection. If the "vinegar" notes dissipate with age, it's probably just normal fermentation byproducts.

I've got a question about this - wouldn't acetobacter likely cease activity after bottling since O2 is now excluded?

Yes - I think it is more likely lactic acid, or possibly even carbonic acid from the CO2.  If it is acetic acid then it is probably coming from a brett or other wild yeast contamination.  That generally requires oxygen too, but if the right co-substrates are available it is possible.

I've judged my share of unintentionally lactic homebrew, I don't remember any that were acetic.

[bbump22]

Acetobacter is aerobic - it often isn't much of a problem if you're kegging/bottle conditioning because there is no oxygen. But if you're cask conditioning and using ambient air to fill the headspace in the cask, then there will be plenty of oxygen in there (and you're probably innoculating with acetobacter too).

+1  - its an issue of oxygen and bacteria, try purging your cask with CO2 unless if you are doing real cask, then there should be very minimal headspace in there.  When pro-brewers barrel age beers, this is one of the biggest issues they face. Too much oxygen along with oxygen can result in A vinegar like liquid...next time, dont dump it and maybe try it out in some bbq sauce...just saying.