Diacetyl in lager - how to clean up

I didn't do the diacetyl rest in my last two lagers. I waited until a few days after fermentation was done and then did the diacetyl rest. I have what I think is a butterscotch taste. I don't think there were enough active yeast to clean up the diacetyl.

I'd like to fix this batch of lager. The lager is kegged and carbonated. From everything I have read, it seems that I should still be able to do a diacetyl rest. This would involve raising the temperature and adding fresh yeast. I'm thinking about buying another smack-pack of the same yeast. Alternatively, I could let it continue to lager for a while but I'm not sure if that will clean up the diacetyl. I've read conflicting information on that.

Any suggestions on what to do?

I had a carbonated ale with the same problem once.

I took the keg out of the keezer, released the pressure, removed the lid and added 1/4 packet of Nottingham yeast then put the lid back on, hit it with some gas to seal the lid. Then I let it sit at room temperature (in the garage) for a week or so until it cleared up the diacetyl.

Any particular reason you chose that yeast? Is that the yeast you originally used for fermentation? I made a big starter last night with some Wyeast Pilsner yeast.

I'd use the starter. I've successfully gotten rid of diacetyl by krausening...adding actively fermenting wort to a finished batch.

How much yeast slurry did you add? I usually decant my starters and just add the slurry. I made a one gallon starter and have four 5-gallon cornies that need yeast. I'm thinking about dividing up the slurry and pitching into two of the cornies, and then do another gallon starter for the other two. Seems like a lot of yeast though.

I'd add at least a couple cups of actively fermenting wort. Kinda like not decanting your starter.

c-note said:

Any particular reason you chose that yeast? Is that the yeast you originally used for fermentation? I made a big starter last night with some Wyeast Pilsner yeast.

Click to expand...

It was the yeast I used to ferment with.

Since your fermentation is essentially complete any yeast additions will just clean up the diacetyl...

IMO, I'd just use what you have on hand. There isn't enough sugar for the yeast to change the flavor any...IMO...

I would agree that if you use a currently active yeast the clean-up will be faster since there's no (long) lag time to be concerned with. :rockin:

How will additional yeast clean up diacetyl if there's nothing left to ferment?

It's not re-fermenting as much as it's cleaning up (or eating) the diacetyl...

My understanding is that it cleans up the diacetyl through the fermentation process. Maybe I'm misunderstanding, though.