How to remove acetaldehyde from Pilsner

[bd2xu]

Posting this in Fermentation and Yeast as well, figure it's a common topic people are interested in...

I brewed a Czech Pilsner on April 15, OG 1.050. Used 2 packs of fresh Wyeast 2278 with a proper starter (used yeast calculator) on my stir plate, oxygenated with O2 before pitching as always. Had a strong fermentation at 50 F, on 6/27 I moved it to 68 F for diacetal rest for 3 days, it was measuring 1.010 and tasted good. I then (6/30) racked to a keg and dropped to 34 F and turned CO2 to 10 PSI. Beer tasted good cold.

I need it for a party on 8/27. I tasted it this weekend to see how it's progressing and HUGE green apple smell and taste, has to be acetaldehyde. Have never experienced this in my ales (about 150 batches) or lagers (this is my 10 lager or so).

What can I do (if anything) to get rid of the green apple taste and smell by 8/27??? Am I screwed? Had HIGH hopes for this beer!

 

[TheHopfather]

Acetaldehyde should age out with time. Problem being you've already kegged the beer. From my understanding yeast will clean up the acetaldehyde provided the beer is warm enough (diacetal rest warm) and given a bit of time. Since the beer is now off the yeast I think your best course of action would be to warm the beer up and let it sit for a while. Hopefully you've got enough time before your party.

 

[ajdelange]

It's easy enough to get rid of the acetaldehyde but the problem is that you might not like the result at least that was what I found when I added acetaldehyde to beer on purpose to see of I could get rid of it by the obvious means: reduction to ethanol by metabite. Metabite does reduce acetaldehyde but it also forms adducts with lots of other things and those don't taste so good.

Acetaldehyde is very, very volatile so you could try sparging the beer with CO2 (pressurize and shake to get a couple of volumes dissolved and then let off the pressure so that the CO2 comes out of solution - do this a couple of times). No promises there so if that doesn't work then try adding minute quantities of sodium or potassium metabisulfite (crushed Campden tablet) solution to some of the beer in a glass to see if you can add just enough to get rid of the acetaldehyde without forming enough of the bad tasting adducts to be noticeable.

I'm afraid I can't be very encouraging here because if you have acetaldehyde coming up to noticeable levels after it has been taken off the yeast it is probable that an infection is responsible. Thus even if you can get rid of the acetaldehyde the beer may not be very good.

 

[LKABrewer]

Acetaldehyde can also be created by the oxidation of ethanol. If this is the case, then it will be really hard to get rid of.

 

[ajdelange]

Well that's true but it doesn't matter whether the acetaldehyde came from oxidation of ethanol or the failure of Zymomonas (which is what I expect is responsible here) to reduce the acetaldehyde which it produces by decarboxylation of pyruvate. If you are suggesting that OP got this acetaldehyde by contamination with an oxidizing agent (hydrogen peroxide, chlorine dioxide, hypochlorite...) then yes, it is going to be difficult to get rid of because the oxidizing agent has to be neutralized (reduced) first and then the acetaldehyde itself has to be taken care of. If OP exposed his beer to an oxidizing agent in such fashion it is for sure ruined - but not entirely by the acetaldehyde.

 

[BBBF]

You can try kräusening it and seeing if the new yeast clean things up.
http://byo.com/mead/item/966-kräusening-techniques

 

[dmtaylor]

Like I said...

Acetaldehyde is a chemical compound that boils at 70 F. If you warm up the keg and purge the gas a couple times a day for a few days I bet you can get rid of it.

https://www.homebrewtalk.com/showthread.php?t=588932