Krausening for diacetyl reduction

[DaveSeattle]

I have a lager (Helles) with excess diacetyl after fermentation and a couple weeks of conditioning. I performed a diacetyl rest at 68 degrees for 3 days but due to travel the beer was already at its final FG when I raised the temperature. I know you can add some yeast at high krausen to speed up conditioning, and as I have an empty spot in my keezer for this beer, I'd like to try this technique.

My question is: does it matter whether this yeast is ale or lager yeast? Also, I assume krausening for this purpose is done at D-rest temperature (65-68 F) rather than at 50 F or 32 F? It seems to me like the fastest way to clean the beer up would be to add some ale yeast at 68 degrees, rather than lager yeast or a lower temperature. Obviously this is not traditional, but I'm a homebrewer. From what I understand, ale yeast should do just as good a job at cleaning up diacetyl. But what say you?

 

[Queequeg]

Sounds like an interesting plan However if memory serves me correctly the first fraction of krausen contains nasty matter that would normally end up left behind on the sides of fermenter.

I also wonder if simply priming the beer as when you naturally carb could achieve the same thing? Perhaps with some more yeast.

The other thing that has just occurred to me is that under pitching can cause significant diacetyl.

Also I'm not certain that the yeast wouldn't still re-metabolise the diacetyl even though fermentation had finished. After all the would still be billions of yeast in suspension.

 

[DaveSeattle]

So you think just warming the beer all by itself would be enough?

You're right about the crud but I think it won't be enough to matter. The beer may have been slightly underpitched but not by much, I used a bunch of repitched yeast from a recent fermentation. I think it just needs more time - time I don't want to wait.

I pitched a 1L starter of alt yeast collected from an active fermentation, so hopefully that does the trick. Pro tip, if you add wort to carbonated beer, do it gently. I didn't and got a volcano.