I’ve been all grain brewing for 9 months now and have noticed a consistent problem with my beer having Diacetyl. Actually, I extract brewed for many years before moving to all grain, but I never noticed a problem before with Diacetyl. I must admit though, that at the same time I started all grain, I also started to learn more about off flavors in beer and started paying more attention to things like Diacetyl and Acetaldehyde, so they may very well have been there before, but I wasn’t skilled enough to notice them. Anyhow, back to my question. What could be causing my consistent problems with Diacetyl? Another thing I’ve noticed is that I don’t always notice Diacetyl in the beer initially, but often times as a keg ages on me, the flavor comes out. Any ideas or suggestions on what I can do to eliminate this from my beer? Other than this problem, my beers have been pretty good.
What are your practives for pitching yeast and fermentation?
What temp do you pitch at? What do you use to steady the fermentation temperature?
The only time I’ve noticed a problem with it is a while back when I pitched the yeast before the wort was cooled down to the fermentation temp.
First off, thanks for the reply.
In all cases, I can’t say for certain what temp I pitch at other than it’s generally below my fermentation temp and at the very least below 68F. I’m talking all Ales here, no Lagers. I have a fermentation Fridge, Ferm-wrap and 2-stage Ranco controller to control my fermentation. At the moment I just use electrical tape and tape the Ranco probe to the outside of my glass carboy, but I’m going to be switching to a thermo-well based on recent discussions with other brewers.
Like I said, the funny thing to me is I don’t pick up the buttery flavor in the beer in most cases until it has aged in the keg a bit. Then it seems to come out. Perhaps I just need to drink my beer faster 
How long do you generally ferment for? Diacetyl is something that the yeast usually clean up after themselves but that cleanup usually happens well after the main part of fermentation is done. If you’re shortchanging your fermentation time, maybe they’re not getting the chance to clean it up.
My ferments last usually a minimum of 3 weeks or 7 - 10 days after fermentation appears to have subsided.
If the diacetyl comes on later, it could be caused by a lactic infection.
Sound like an infection to me, I agree with Denny
Diacetyl
This compound is responsible for an artificial butter, butterscotch or toffee-like aroma and taste. At low levels, it may also produce a slickness on the palate. A significant number of tasters cannot perceive diacetyl at any concentration, so every judge should be aware of his or her limitations. Diacetyl is a fermentation by-product which is normally absorbed by the yeast and reduced to more innocuous diols. High levels can result from prematurely separating the beer from the yeast or by exposure to oxygen during the fermentation. Low FAN levels or mutation may also inhibit the ability of yeast to reduce diacetyl. Note that high fermentation temperatures promote both the formation and elimination of diacetyl, but the latter is more effective. For that reason, lager breweries often employ a diacetyl rest, which involves holding the beer in the 50-55 F range for a few days after racking to the conditioning tank. Diacetyl is also produced by some strains of lactic acid bacteria, notably Pediococcus damnosus. Low levels of diacetyl are permissible in nearly all ales, particularly those brewed in the United Kingdom, and even some lagers, notably Czech pilseners.
I, too, had a similar issue with some kegged beers getting buttery over time. I also chalked it up to bacteria in the kegging system. So, I cleaned the dip tubes, then filled the kegs with boiling water left for about an hour (make sure to release the air out of the dip tube so that water gets inside). Then an iodophor bath for another hour.
Symptons gone.
Thanks guys. These are good thoughts. I like to think I’m a pretty clean brewer, but perhaps there is something in my sanitation processes that needs to be tightened up a bit. I’ll follow your advice on cleaning my kegs and see if that has a positive effect. Thanks again. Cheers!
I went through a persistent low level infection for almost a year before I knocked it out. I switched to StarSan and I think that’s what got rid of it. Of course, if you already use StarSan, disregard that advice!
But the real nugget of advice here is to switch sanitizers. If you use StarSan switch to Iodophor for a bit, etc.
On a suspected infection, sanitize with several methods
Chlorine bleach, old school but effective, rinse well
Starsan
then Idophor
consider a boil if that is possible for much of your plastic.
Don’t overlook the obvious, he could be hypersensitive to diacetyl and once he learned what that flavor was it became even more pronounced. I’m in with the rest of the crew, sounds like a sanitation issue, but if you switch sanitizers and it doesn’t change, it’s probably your palate.
Having worked in a brewery lab, I think the only way to know for sure if the diacetyl is a result of bacterial contamination (Lactobacillus or Pediococcus) is to put some onto a plate of SDA or into HLP (I think you can buy these from White Labs). With proper sanitizing, the most likely cause is that the yeast did not uptake the diacetyl–can be removed with bottle conditioning (or also keg conditioning), or doing something like a diacetyl rest–even in an ale.
What type of yeast do you use? Some English yeasts produce a lot of diacetyl.
+1 - very common with many English strains. If you are getting diacetyl from WLP002 - well, yeah, the yeast is the problem. WLP001 - 'nother story.
Another thing that was not mentioned is that aeration during transferring can cause diacetyl to re-form. I can’t remember exactly why this is but it can be an oxidation problem post fermentation. Or so I’ve been told.