Diacetyl in kegged lager

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zacster

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I brought some samples of my kegged lager to a homebrew swap last week and 2 people immediately said there was diacetyl in it. I could taste it myself.

My process this time had me ferment at cold temps using Munich Lager 2308, starting at 45 and ramping up to 52, and then doing a d-rest. The problem was with the d-rest in that I think I let it go too long at cold temps, and then when I did the d-rest the weather got frigid outside, and my brewing space got cold with it. I don't think it ever went above 58. Then on top of that I was leaving on a trip for a few days. Before I left I put the dry hops in and lowered the temp again to cold crash. When I returned I kegged it and added Biofine to it to get it clear. I could tell when I did that there was an off taste.

So now, after about 2 weeks, the beer is crystal clear but it still tastes of diacetyl. Should I bring the keg up to room temp for a few days or a week? Should I add some yeast back since it looks to have fallen completely out? Is there any hope for this brew beyond drinking as is? Should I just wait it out for a few weeks, there is plenty of Stella in my fridge. I want this batch to be good.
 

VikeMan

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So now, after about 2 weeks, the beer is crystal clear but it still tastes of diacetyl. Should I bring the keg up to room temp for a few days or a week?

I would.

Should I add some yeast back since it looks to have fallen completely out?

Normally, I would say that isn't usually necessary. But you used biofine, which probably removed yeast more efficienctly than just time and gravity would have. If you decide to add yeast, I'd add active yeast, i.e. krausen it.
 

VikeMan

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I've read a ton on diacetyl, as I thought it was an ongoing issue in my beer when I started brewing, and most findings say reduce the initial diacetyl by boiling longer, leaving lid off, doing a D rest etc, but nothing about removing it once it's in the keg.

Just FYI, Diacetyl has nothing to do with boil length or kettle lids. That's Dimethyl Sulfide (DMS).

Diacetyl can definitely be cleaned up in kegged beer by warming up, if there's enough yeast left. If not, krausening will do it.
 

wepeeler

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Just FYI, Diacetyl has nothing to do with boil length or kettle lids. That's Dimethyl Sulfide (DMS).

Diacetyl can definitely be cleaned up in kegged beer by warming up, if there's enough yeast left. If not, krausening will do it.
Poop. Totally confused the two...

Cheers!
 
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zacster

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I've shut the fridge off and I might pull the keg into a warmer part of the house. Since it is in the keg I can put it in the sun room since light won't reach it and that is the warmest spot. And since it is completely clear it won't get stirred up by the movement either, but it also may not have any yeast left in it, or very little.

I've made so many lagers and this is the first one to have it. The d-rest was always done at the proper time in the past. I'd have been better off leaving it at 65-68 when I was away since it would be otherwise undisturbed.
 
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superiorsat

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I would think adding active yeast would probably be in your best intrest. I had a couple stubborn Oktoberfest beers ( split batch different yeasts ) last year where I did the warm up for a week or so. Thought I had resolved the situation only to have a lesser diacetyl taste slightly creep back in after drinking for a while. If I had to do it again I would have added some active yeast.
Edit- only 1 of the 2 had the diacetyl even though they were in the same fermentation chamber at matching temps.
 
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zacster

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If I add yeast, should I pressurize it in the keg? I'd have to buy the yeast too since I don't ever keep it. I don't make enough beer to make it worthwhile to save it. And based on other comments I should kick it first in a starter to get it active.
 

superiorsat

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If it was me I would get the yeast active with a starter. Your beer is already carbonated so it should stay pressurized. However I think I would consider burping it now and then just to decrease the PSI as to not add too much added stress on yeast. They are already going to be in a pretty desolate environment as the keg fermentation is complete and they are just there for clean up duty. You will obviously have to carb back up after the process and don't know how long a period for re-clarification to happen after the new yeast addition.
 
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zacster

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I just took a taste, I'd forgotten that I could just stick the tap on and take a quick bit, and it has definitely mellowed after 5 days. I'll leave it for another few and then stick it back in the fridge. I didn't add yeast as I couldn't figure out how to do that without depressurizing as I don't have a second keg or anything else that I could put under higher pressure to force it in.
 
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zacster

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I tried again last night and while it may have mellowed a little, I still taste it. I put it back in the fridge and I'll see how it is cold. If it is still bad I'll have to depressurize to add yeast and put it back on immediately. I hope my tank still has enough gas in it, but that's easily fixed too.
 

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If you are starting at 45F, try pitching and fermenting at 48F and holding it there the whole time, combined with pitching at a large rate (2B cells per ml per degree plato, Brewers Friend yeast calculator is good calculating that)...supposedly pitching and fermenting that cold with a large yeast starter prevents the chemical precursor to diacetyl from ever forming, thus no need for a d-rest. I have done it plenty of times and it seems to work.
 

VikeMan

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FWIW, diacetyl's precursor (α-acetolactate) is formed in every fermentation. It's an intermediate step in Valine synthesis.
 
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zacster

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I did a 2L starter which according to BeerSmith comes out to 378B cells and that is the number that Brewers Friend gives me now. I've done the ramp up from 45 to 50 before and it always gave me clean beer, but I also did a D-rest at the proper time, but I also remember thinking it didn't really need it because I couldn't detect it in prior batches. Maybe it is the yeast variety, I used Munich Lager when I've used Bohemian Lager in the past.

I'm going to accept the fact that I probably needed a D-rest on this batch and probably didn't achieve it due to the frigid weather making my beer pantry too cold for it. Next time I'll drag it into my warm dining room where it has a chance, or just brew in the summer. In the meantime I'm going to get some yeast and make a small starter with it and pitch it once it takes off. What's the worst that could happen? The beer isn't good the way it is now. I've been making lagers for years now and this is the first time I've had diacetyl in the finished product.
 
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zacster

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I put the yeast in after having it in a starter for about 10 hours. It was pretty active already. I'll let it sit for a week or so and then stick it in the fridge. I hope the yeast will fall out again because it was so clear to begin with. Usually the first draw on it will get most of it and the next few will be less and less cloudy.
 
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zacster

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Wow, it worked! I can't taste it at all now. It's been 5 days. I'll let it sit for another couple then back in the fridge.

Ironically, the weather got frigid again and would have made the pantry too cold except this time I brought it in to a warm room.
 
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zacster

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And it really close it out, the keg kicked yesterday. I didn't realize I was even drinking so much of it. Time for another batch, but maybe I'll do a 3 gallon batch on the induction burner as I proposed in another thread somewhere. I've only ever done 5 at a time.

In the end the diacetyl was a non-issue. It just got better with each pour.
 
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