Diacetyl

[coffeeman]

You could try warming up the keg to encourage diacetyl uptake, or krausen it with a fresh active pitch to clean it up.
If it's bacterial you are screwed.

[ajdelange]

If it's bacterial it won't be subtle. This used to be called Sarcina Sickness. And yes, if it's Sarcina Sickness, you are screwed.

I used to pitch cold and then warm up to 48 - 50 for lager fermentation but now I just pitch at whatever temp the wort comes out of the heat exchanger (usually around 50 - 52) with the controller set at about 48°F. I do this not because I don't like the cold pitch scheme but because I pitch inline now. I do not do diacetyl rests and do not, AFAIK, have diacetyl problems. At least no one has reported them to me. I stopped checking for it because it is a PITA determination and I always got results right around the minimum level of detection for the test. It, of course, strain dependent to some extent.

It is also, perhaps unfortunately, a fact of life that as beer ages its diacetyl level increases (after having decreased during lagering). I have not experienced this either but my beer is stored, for the long term, over yeast so they may keep re-processing it even after as much as a year. I am noticing that a Pils done with the Budvar strain is now, after more than a year, beginning to taste very much (more than it did) like Budvar and part of the Budvar profile depends on diacetyl right around the threshold level (makes the beer taste caramelly) so perhaps in this case (extra long storage) I may be seeing diacetyl upswing. Perhaps the yeast have finally given up the ghost but I haven't detected autolysis (yet). Unfortunately, the next mug of that beer could very well be the last - it's got to be about finished by now.

[Millhaus]

Sounds like you have good fermentation technique to nail 8 lagers previously. Did you pick any oxygen on transfer? I had a lager once, no diacetyl after fermentation but I think I got some O2 when I transfered to the keg. Nothing more disappointing than tasting the beer after fermentation and knowing it is great and then to taste it out of the keg and realize you picked up something during transfer.

[ResQ]

This is actually a great topic. Thanks BNB. I am currently going to transfer my Mexican Coffee lager (inspired by the new Zymurgy "montezumas revenge") today to crash down to lower 30*s, and was wondering if I should do a D-rest before doing so. I fermented around 55-58* with the whitelabs san fran lager yeast. but the temps were in the mid-upper 50's?

[philbrasil]

On my previous 2 corny´s I had the same thing going: first 3 or 4 pints and I can taste diacetyl. After that, and it´s pretty clean. Do you think it could be that I this diacetyl I am noticing is on the yeast that comes with the first few glasses? Then after my beer has cleared a bit, the yeast is no longer there? I don´t know, that´s my theory...

[Mylo]

Any ideas for troubleshooting based on the info given?

You bought your yeast at Chuck's.... didn't you....?

My work here is done.



Mylo

[944play]

I've had similar experience with 830 (and W-34/70) going all buttery in the keg. I'm told this may have something to do with oxidation during racking. I'm not so sure about that, but it's as good an explanation as anything. The one time I got zero diacetyl with 34/70 was when I kraeusened the keg with a liter of beer at high kraeusen.

Now I use 2308 and never taste diacetyl.

[ajdelange]

I've had similar experience with 830 (and W-34/70) going all buttery in the keg. I'm told this may have something to do with oxidation during racking. I'm not so sure about that, but it's as good an explanation as anything. The one time I got zero diacetyl with 34/70 was when I kraeusened the keg with a liter of beer at high kraeusen.

Remember that yeast don't produce diacetyl. They produce acetolactic acid which then gets (nonenzymatically) oxidized in the beer. If yeast cells are still present they will take up the diacetyl and reduce it (enzymatically) to acetoin and then to 2,3 butane diol. So there are basically three things you can do. 1) Prevent acetolactic acid formation (tough to do but some yeast strains produce more than others and cold pitching seems to work to some extent). 2) Protect the beer from oxygen to the maxium extent possible. 3) Make yeast available and/or establish conditions that make it easy for them to reduce any diacetyl which does get formed. Item 2 is, of course, something you should strive for diacetyl or no. Kreusening, diacetyl rests and long lagering over yeast are all variations on the theme of 3). As more people are moving to cylindroconicals it becomes easier for them to realize 2) by counterpressure transfer from fermenter to keg. Just be sure to do it before all the yeast have dropped out. After all the diacetyl has been formed and reduced you can rack off the yeast to another keg but there is really no reason to do this unless you want to move the beer or must remove it from refrigeration before it is consumed.