Diacetyl still in Pilsner

I brewed an Imperial Pilsner back in January, did a d-rest for 3 days and let it lager for about 7 weeks. I racked to a keg about a week ago and just sampled it today and there is still some noticeable diacetyl in the.

I have searched and there seems to be different opinions if the lager process will clean up the remaining diacetyl or not. I plan on bottling with my beer gun, but don't know if I should do it now or not.

Will the remaining diacetyl clear over time in the bottles? Or should I repitch with a yeast starter to clear it up?

The OG was about 1.070 and I used WLP802.

I'm not a lager expert, but if you still have the diacetyl after 7 weeks it might be time to pitch with a clean fermenting yeast. I would do that, and give it time to work, before bottling. You're better off doing this on a bulk basis, as you are any corrections.

climateboy said:

I'm not a lager expert, but if you still have the diacetyl after 7 weeks it might be time to pitch with a clean fermenting yeast. I would do that, and give it time to work, before bottling. You're better off doing this on a bulk basis, as you are any corrections.

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I agree. Diacetyl, probably won't go away and if it does it will take a LONG time.

Ok I will prob repitch a starter to finish it up. I'm thinking a clean ale yeast would work, or should I go with the same lager yeast? I think maybe WLP001 would work fine and be a little quicker.

You should go with the same yeast strain used in the beginning, its ok if you leave it slightly warm to promote cleaning up activity.

An ale yeast may put some flavors you did not intend in there.

I agree with pitching more of the same yeast before bottling. Here's an anecdote: I recently made a bock rauchbier, kegged it, lagered at 38F, and it had huge diacetyl after 4 weeks. Totally undrinkable. I simply shook it up (to rouse the remaining yeast) and set it on its side (in a bathtub in case of leaks) at 64F for 2 weeks with an occasional shake. Worked beautifully! Turned into a great beer. I'd say if there's still yeast in there, you probably don't need to pitch more.

This was WLP 833, German Bock.

Applying a krausening technique may help reduce what you're picking up as VDK's. It won't go away with age.

Next time, pitch cold (mid 40's), use the correct amount of healthy yeast (550B cells, or a 4L starter), use pure O2 to oxygenate and you won't have any diacetyl to worry about.

SpeedYellow, thanks for your post - now I'm a little more confident. I kegged a light american/german lager last week - it developed diacetyl at the last moment in the carboy, I was dry hopping it too so I had to get it off of the hops. So after kegging, I simply left it sitting in my kitchen, at room temp, and periodically I pull the pressure valve a bit to release excess CO2 for the yeast's comfort. It's been a week, and the diacetyl is still present but noticeably less. Just a bit more time...

DoctorDuvel said:

SpeedYellow, thanks for your post - now I'm a little more confident. I kegged a light american/german lager last week - it developed diacetyl at the last moment in the carboy, I was dry hopping it too so I had to get it off of the hops. So after kegging, I simply left it sitting in my kitchen, at room temp, and periodically I pull the pressure valve a bit to release excess CO2 for the yeast's comfort. It's been a week, and the diacetyl is still present but noticeably less. Just a bit more time...

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Glad to help! Seems that folks here report mixed results with this method, but it worked for me in that case. Don't know what the driving factors are there, maybe it's the yeast strain. Probably unrelated to yeast amount, since I had very little yeast in the keg. Maximizing yeast surface area by tilting on its side can't hurt, but who knows if it really helps. Extra time here probably can't hurt either.

I would bring up the temp first, see if the yeast still in the beer will reduce the diacetyl.

Only if that doesn't work, pitch yeast at high kraeusen.

You didn't say what kind of Imperial Pilsner you brewed, (German,Bohemian,Classic American), and you didn't state much about your yeast and other ingredients, which would help determine if your beer would have had some diacetyl character at "normal" gravities.
I think you can surmise that if your style (when brewed at classic gravities) would have diacetyl notes, (which is acceptable in Bohemian Pilsner) that an "Imperial" version is likely to have a more noticeable diacetyl presence.