an apple a day

[mr.jay]

My golden ale seems to have a bit of acetaldehyde in it. It is the most strait forward beer I brew, and I wonder if all of my beers suffer from this (masked by their monster hop and malt aromas).
I've been dealing with this mild green apple flavor for quite some time, but I'm always looking for was to improve my craft as a brewer. While I understand low levels of acetaldehyde are acceptable, what can I do to reduce it? Perhaps I'm doing something wrong? Perhaps you need more information? Perhaps I can post the info needed to assess the problem? If anybody can provide some insight into this, I will tell you all you need to know about my B.H. procedures.

[bbrodka]

Green Apple (Acetaldehyde) Aroma or Flavor
Cause:
Acetaldehyde is produced during fermentation. It is very common in a young beer. It is more evident in the aroma and flavor when either cane or corn sugars are used. Normally the acetaldehyde will dissipate over time as the sugar is further fermented. Sometimes it is caused by bacteria due to poor sanitation procedures.

Corrective Action:
Age the beer another week or two; if the acetaldehyde disappears, then there is no problem. Otherwise, reduce or eliminate the use of cane or corn sugar (substitute DME if necessary). Always watch your sanitation procedures throughout the process.

[ECB]

What about underpitching and too warm temps during ferment?


Tom

[beauxman]

How long is your maturation period after primary fermentation has stopped?
-Beaux

[SoCalBrewer]

Temps

I have the same problem right now and I am positive it was due to fermentation temperature. Check out the book Yeast for some data. Chris White tested 2 batches of beer fermented with 001 at 68deg and 74deg. The 74 deg batch had numbers that were orders of magnitude higher.

We are going to wait a few weeks then I will likely pump in some krausen if time doesn't do it. Stay tuned....

[monkeybrewer]

yeast strain

In beers that I've tasted that have a big green apple character there has almost always been one connecting factor...Ringwood yeast. If you're not using Ringwood then maybe you've had a bit of a mutation and the yeast isn't re-uptaking the acetaldehyde produced during fermentation. Just a thought...
Cheers

[MJMurphy]

If you are noticing it later, say in the bottle/keg or serving tank, you might be running into something we saw. We found that after some several weeks a bit of acetaldehyde was cropping up. It wasn't there during fermentation and it wasn't there early on in the life of the beer, but it was there later.
As has been mentioned, acetaldehyde is present in fermentation.

It normally declines below a notable level, however, some can become bound up with sulfur dioxide and remain in the beer. Later, oxygen can come along and free the acetaldehyde, thus giving back the green apple.

Our running theory was that over-production of SO2 was binding up the acetaldehyde and the slow ingress of some oxygen later in the beer's life was freeing its inner Granny Smith. This particular beer and yeast does go through some ups and downs with SO2, but it fades rather quickly even when it is present. Apparently there were some issues with it that persist even beyond the initial sensory troubles.

Are you able to test for micro? Some bacteria can produce acetaldehyde and may persist if you serial re-pitch for multiple generations.

I would keep an eye on wort nutrients - make sure you have enough FAN, zinc and calcium and monitor your fermentations to ensure you are getting consistent rates and cell counts, that can help with the SO2. You could also play with oxygenation rates, increased yeast mass can help clean up acetaldehyde.