Krausening an already-primed keg?

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Shawn3997

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My latest Oktoberfest lager seems to have some diacetyl in it and I'm going to chuck some krausening starter in to remedy this. The keg is at room temperature but is already gassed up to 2.7 volumes. If I make a 1.25L starter using 125g of DME and then toss this in the keg and seal it up am I looking at any issues keg-pressure-wise? I'd assume the pressure relief valve would just pop at 50 psi if there was an issue but I thought I'd check here online as well.
 
My latest Oktoberfest lager seems to have some diacetyl in it and I'm going to chuck some krausening starter in to remedy this. The keg is at room temperature but is already gassed up to 2.7 volumes. If I make a 1.25L starter using 125g of DME and then toss this in the keg and seal it up am I looking at any issues keg-pressure-wise? I'd assume the pressure relief valve would just pop at 50 psi if there was an issue but I thought I'd check here online as well.

The thing is, co2 is poisonous to yeast, and a high level would halt yeast activity. So make sure you de-carbonate the keg before adding the starter. I don't think you'll get a ton of pressure from such a tiny amount of DME, but you may want to consider 'burping' the keg during that time if you don't have a spunding valve.
 
The thing is, co2 is poisonous to yeast, and a high level would halt yeast activity. So make sure you de-carbonate the keg before adding the starter. I don't think you'll get a ton of pressure from such a tiny amount of DME, but you may want to consider 'burping' the keg during that time if you don't have a spunding valve.

Not really, especially considering diacetyl reuptake occurs during the terminal phase of fermentation after CO2 and ethanol are produced. Otherwise naturally carbonated beers would contain diacetyl as a result.

The addition of that small amount of krausen is projected to raise the CO2 level by around 0.7 volumes (assuming a 5 gallon keg), so you’ll probably have to spund or burp the keg a few times to stay within style. I’ve krausened a carbed keg for this exact reason and it definitely works...just be patient.
 
Ha, it was impatience that got me here in the first place. I'm pitching tomorrow so we'll see if it blows up or not then. :O
 
OK, just to follow-up on this: I made a 2.5L starter of 34/70, let it get active, then pitched about a liter of this into the keg. I would have added more but didn't have room in the keg. I brought the keg to room temperature and 2 days after pitch I checked the PRV and only got a little hiss so I just left it alone. Yesterday I popped the keg back into the keezer and tonight I poured a beer and voila, no buttery taste. Very nice, very smooth beer. Quite tasty!

So in the future if your beer is buttery-scotchy, try adding an active 1L starter for a few days at room temperature for a quick fix. The beer, if someone wants to know, was HBA's Oktoberfest: https://www.homebrewersassociation.org/homebrew-recipe/ag24-oktoberfest/

I do remember I used Victory instead of biscuit and brought the IBUs up to about 30 and I also added a pound of Vienna and then scaled everything down to a 1.056 beer. Water was RO with CaCl. If I were to make this again I'd add another 1/4 of Caramunich just to balance everything but overall, a perfect beer for this time of year.
 

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