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Oops - Skipped my diacetyl rest. Now what?

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I made a Kolsch with 2565 with an 8 day primary fermentation at 60F, then racked to a secondary for another 7 days at 60F then took it to 45F to get the yeast to floc. The next step is to slowly drop it to 32F. This schedule was recommended by another brewer more experienced with lagers than I.

Anyway, I somehow dumped my first hydro sample when I racked to secondary and didn't sample it again until now (at 45F.) The problem is, I can taste diacetyl. It's not strong, but definitely there and if it remains at this level, it will not be to my liking. I'm certainly more sensitive than some to diacetyl, so again, the levels aren't high, but detectable and I'd rather have them cleaned up a bit.

So, my question is what to do?  Is it too late to do a diacetyl rest? I brought the beer back up to 65F last night and the yeast were rousted a bit from me moving the carboy. I didn't want to roust too much because I've been told 2565 is a b**** to floc, and that was the whole point of the crash from 60F to 45F. Should I add some yeast nutrient to get them active again?  Or should I have just left it alone?

From what I understand about lager fermentations, the yeast stay active even at lager temps, so should I just drop it slowly to 32F and wait it out?  Will it clean up?  If so, what's the point of a diacetyl rest?  What level of diacetyl do you have to be at before you have to worry about it not cleaning up during lagering?


I don't have enough Kolsch experience to really say, but I think I agree w/your approach of slowly dropping to 32° and waiting longer for it.

Let the beer warm up and see what happens. If the diacetyl is not gone in a few days, rehydrate some dry yeast and add it to the beer.

Don’t cool down the beer. Even if you do it slowly the yeast may go dormant.



--- Quote from: Kaiser on February 25, 2010, 03:45:15 PM ---Don’t cool down the beer. Even if you do it slowly the yeast may go dormant.

--- End quote ---

Thanks Kai.  That's one of the things I don't understand about lagers. I thought that dropping the temperature slowly was so the yeast weren't shocked.  That implies that some of them are still active during the lagering period.  Is that dependent on the yeast strain? Do some strains finish earlier than others? If they are active, what are they doing during this phase of the ferm cycle?  Same things as ale yeasts during the conditioning phase of ferm?


I've had pretty good luck removing diacetyl by krausening....adding a qt. or so of actively fermenting wort.  Kinda like what Kai suggested, only already in action.


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