I just got some score sheets back from a competition and the judges picked up a diacetyl aroma. The beer is an 11.5% RIS that is fairly new in the keg (brewed in July). I have kept it cold as well.
What I am wondering is, will the diacetyl age out since this is a big beer that is so young? As always, thanks for the feedback.
On another note, I will be kegging my first Brew Tan B beer- a brown ale. Can’t wait to see.
The yeast cleans up Diacetyl, so if you have some yeast it may clean up in the keg. One way to see is to get the yeast off the bottom and resuspended by turning the keg upside down. The viability of the yeast in a big beer may be an issue.
Hope that helps.
You could also krausen it…add about a qt. of actively fermenting wort.
Just what I was thinking.
In case its not clear, the yeast will work on diacetyl if they are active. That means the beer must be warm enough for the yeast to actively work on the diacetyl.
Might be tough for the tired yeast on a strong ABV% RIS though. At least for any residual yeast still in the keg.
Steve,
Can acetaldehyde be cleaned up in the same way - time, warmth, yeast present?
I agree it might be tough on the yeast for a big RIS, but even if you Krausen or repitch, warm temps would favor diacetyl reduction. And, yes, I think it would work on acetaldehyde too.
How much diacetyl are we talking about here? If the OP didn’t notice it himself, why not just leave it. RIS might be enhanced by a little butter.
I agree with this. I like a little diacetyl in this style, so much that I brew mine with Ringwood yeast. 
This is one of my gripes about the BJCP/Craft/homebrew judging.
Diacetyl isn’t evil, and should be found in some styles. I don’t have any data on it, but I’d imagine that some oldschool RIS beers had diacetyl, being brewed in England after all. I know the BJCP says “no diacetyl” for RIS, but I don’t know that I agree. I feel they too often lean towards describing American interpretations of styles, rather than the actual beers themselves.
Case in point: Northern English Brown Ale. “Very low to no diacetyl”.
Ever had a Samuel Smith’s Nut Brown Ale? This beer is often used to show folks what diacetyl tastes/feels like. There’s nothing low about the diacetyl in that beer, and in fact it’s an important part of the beer’s flavor. Even the BJCP listed this beer as the “second best” example of the style in their old guidelines, but yet “low to no diacetyl” is appropriate for this style?
Granted, all this is just my personal opinion, but this is why I have zero interest in the BJCP or competitions.
I tasted a sample the other night and thought I picked up diacetyl but I need some serious work on recognizing and understanding these off flavors. I am not sure if I noticed it because of confirmation bias or if it really is in there now.
Another interesting note is that the same beer was judged in a comp about three weeks prior and diacetyl was not mentioned. I think I will have some others try it and see what they think before making any changes.
[quote]I think I will have some others try it and see what they think before making any changes.
[/quote]
^this++