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Posted: Tue May 24, 2016 10:49 pm
The beer is already carbonated (I transferred and spunded before final gravity was reached). I wasn't going for carbonation but the other benefits. To quote the Edelstoff blog "Kräusening is used to assist the fermentation to break down compounds such as Diacetyl (amongst other products) and produce a more rounded, polished beer." His summary followup "Don’t forget to Kräusen, it’s perfectly ok to do this even after secondary fermentation is complete." leads me to believe there may still be some benefit.
One impetus for the idea is that I'm starting to taste a noticeable amount of diacytel in samples pulled.
I'm thinking ideally though it sounds like a good idea to add to the receiving keg during a transfer as, presumably, the fresh active yeast will scavenge any o2 picked up in the transfer even faster and aid in the final push.
Posted: Wed May 25, 2016 12:12 am
More followup after some evening Kunze:
Kunze (184.108.40.206 - Cold Fermentation Cold Maturation) states: Many breweries deliberately add krausen at transfer to improve the foam and flavor. For this purpose the beer is almost completely fermented in a vigorous primary fermentation and this beer, without the now sufficiently sedimented primary fermentation yeast, is transferred with about 10 to 12% krausen at about 5c (which is 41f).
Krausening produces high quality beer but the primary fermentation yeast should be removed as completely as possible, otherwise it spoils the beer.
So, in my situation, I transferred at 72% EVG and the beer cleared quick (before I could even drop to the 30s) so I imagine I transferred less yeast. It's strangely much clearer than the Helles next to it that is 2 weeks older - initially I had a tough time picking them out blind but now that the older one is cleaning up the diacytel is coming through in the younger (tho bright) beer. Seeing as Kunze recommends the Krausen added at 41f my current temperature should be solid. But, again, it sounds like ideally this process would have been performed on transfer.
My goal is to clean up the beer (diacytel particularly, I enjoy a touch of sulfur) and if the purported benefits of better foam and flavor (Kunze) are true as well all the better.
Posted: Wed May 25, 2016 7:46 am
Ok, Diacetyl.. I get it now!
Posted: Wed May 25, 2016 8:32 am
You can add krausen any time you transfer between vessels. The yeast will clean it up if you just give it some time. I'm not sure it's worth opening up the vessel at this point. For cleanup duties, you'll be fine with 10-25 ml of yeast slurry pitched into 100-200ml of wort. Make sure it's really active, as your beer is already has alcohol and is carbonated. I wouldn't waste a brand new vial on it, though.
Posted: Wed May 25, 2016 9:17 am
Posted: Wed May 25, 2016 9:27 am
I don't have the headspace to add more liquid to my kegs, so I add the krausen during the transfer to spunden. It sounds like you are set up well to do it though. If I had your setup, I would fill my boil kettle with 2L of extra runnings (may require tweaks to the calcs) and after the wort has boiled 30-45 minutes, I would transfer the extra volume to sterile canning jars. That way I'd have wort from the actual batch to add as krausen.
A white labs vial only has ~30ml of yeast. Even if you grow/pitch 4-5 times this volume, you're talking 120-150ml of yeast for an entire batch. Cleanup duty requires a lot less, maybe 10%. Pitch more if you are concerned. It won't hurt, it'll just flocc out and be more yeast mass in the bottom of the keg.
Look at the thin film of yeast in a bottle of Sierra Nevada. It doesn't take much.
Posted: Wed May 25, 2016 12:58 pm
Make sense. Trouble is I don't have a setup to can properly and IIRC Kai mentioned how he was going to stop using canned wort for Krausening since he believed oxidation was becoming a factor. But I feel comfortable enough brewing up a tiny batch of the same recipe (may smooth out any variances) if needed.
As far as yeast management goes, atm I am storing ~1qt of slurry (basically all that's left after I rack to lagering) which seems to contain ~200ml of thick yeast in a mason jar in the fridge. If I'm going to use some for a fresh batch and some for krausening maybe I'll pull some off into a smaller jar after racking.
Posted: Wed May 25, 2016 1:32 pm
Posted: Sun May 29, 2016 4:29 am
Kräusening is generally performed with yeast in its high log phase (high propagation stage). When doing regular brews with the same recipe, then performing this is easy. You just transfer it from some other fermenter.
The volume needed is quite noticeable (~12%) so there will be quite a flavour impact if you use different wort.
The simplest thing would be to stow away some of the original wort and ferment it a few days later. Or just keep a 3 day brewing schedule
However, the more I became better at cold fermentation the less I needed this emergency procedure. Nowadays I'm perfectly able to ferment decent Bavarian Helles without having to bother with such elaborate techniques.
If I'd brew on a regular schedule like a brewery, then I'd certainly do this routinely. But when not I am not sure whether it's really that important. It may be time better spent nailing that secondary so that one doesn't need this insurance policy in the first place.
Naturally, every one has their own preferences and observations. Either way, if you've never done it and are curious about it then give it a shot!
Have a good look at Kunze 220.127.116.11 and the preceding paragraphs.
Posted: Mon May 30, 2016 10:13 pm
Appreciate the advice, reading through the Kunze sections, does Narziss offer any more insight?
I kind of like the idea of combining drauflassen with a ~12% krausen upon transfer for more consistency, practice brewing the same recipe, and kitchen friendly batch sizes.
2.5 Gallon initial batch, another 2.5 gallon batch a day or 2 later, then transfer 4.5 gallons to lagering keg where it will meet 0.5 gallon of krausen. Fresh yeast introduced at 3 stages. But that requires quite a rigorous brewing schedule.