[gimmeales]

After thinking it was a keg sanitization issue the first go-around, brewed another identical batch of cold IPA. Recipe is 100% Bohemian Pils, 13.5oz total hops with 6oz added 4-days into a vigorous and nearly complete fermentation with Saflager 34/70. Raised temps to 68F for 48hrs (87% attenuation). Cold crashed after that (removing the bagged dry hops) for several days before racking onto biofine in a keg for another ~5-days @ 34F. It's about a 2.5 week turn-around time which sounds roughly like what the commercial guys are doing. However, I'm getting hints of buttery-ness already I've gone nuclear on my kegerator lines (short of replacing them), but wondering if recipe, process, or sanitization is the most likely culprit here? (not much lager experience, but have made pretty clean 'quick' lagers in similar timeframes with 34/70)

[majorvices]

You could try a forced diacetyl rest (pull small sample and hold at about 140F for 15-30 minutes then cool back down. If you pick ups diacetyl then you need to rest the beer at warm temps longer and this usually clears it up. I've had issues with 34/70 and diacetyl in the past as well, though I definitely think it is a great yeast.

The one thing that struck me was "removed hop bag" which sounds like creating a lot of dissolved oxygen in the beer to me. If the precursor to diacetyl is in the beer oxidation can cause diacetyl to form even though the precursor is flavorless and not detectable by sensory. I'm not sure how you would remove a hop bag without creating a lot of DO.

[dmtaylor]

Here are the things that are true but which hardly anyone will ever tell you:

Yeast eats diacetyl, but 48-72 hours isn't long enough for the yeast to eat it all.  In my experience it often/usually takes closer to 3 weeks.  By cold crashing and racking, you've removed most of the yeast which could have eaten the diacetyl quicker.  Your best bet now is to keep temperature in the 60s for at least 2 more weeks, maybe even 3 or 4.  Taste it occasionally until the remaining yeast has enough time to eat it all.  THEN you can chill it back down and enjoy.

[majorvices]

The precursor to diacetyl is alpha-acetolactate which is flavorless. If the yeast have not consumed all of the alpha-acetolactate it can definitely create diacetyl in your beer after packaging, even if it wasn't;t there before. Oxidation (like removing a hop bag from a fermenter of secondary, or using a secondary which should be avoided, both of which seem like oxidation potential to me) can cause the transformation of alpha-acetolactate to diacetyl. If too much alpha-acetolactate is created during fermentation the yeast may not be able to reabsorb all of it, though that is under extreme circumstances.

dmtaylor's suggestion of resting longer is spot on. In commercial brewing practice when lagers are rushed to get out the door a forced diacetyl test is a great tool to see if the precursor alpha-acetolactate is still present. The forced test will essential force the alpha-acetolactate to convert to diacetyl if it is present. If the beer passes the test (no smell or taste of diacetyl in sample) it can move to BBT and package. If not then an extended rest always solves the problem unless the diacetyl is from an infection.

[MNWayne]

I avoided dry hopping for a long time due to oxygen ingress potential.  My solution is to use pellets for dry hopping.  I add them with CO2 flowing into fermenter and remove them using bottom dump valve while under low CO2 pressure.

[gimmeales]

Great stuff everyone - thanks! Sounds like my best bet is to warm up the keg for a couple weeks and see where that lands me. It's already partially carbonated in the keg, can the diacetyl be cleaned up in a pressurized vessel, or should I vent the lid (maybe leaving it open) for part of the cleanup period? Also, since most of the yeast has been removed (though it's still somewhat hazy)would adding another sachet be beneficial? It's sitting at 1.007 and ~7% ABV.

FWIW, I was very gentle and slow in removing the hop bag (from fear of oxidation), but also did not want to leave hops in the beer another week and risk extraction of undesirable 'green-ness'. I am new to the 'dry hop during fermentation', but sounds like I should have just left them in and changed my racking schedule if I was concerned over-extraction.

[denny]

Here are the things that are true but which hardly anyone will ever tell you:

Yeast eats diacetyl, but 48-72 hours isn't long enough for the yeast to eat it all.  In my experience it often/usually takes closer to 3 weeks.  By cold crashing and racking, you've removed most of the yeast which could have eaten the diacetyl quicker.  Your best bet now is to keep temperature in the 60s for at least 2 more weeks, maybe even 3 or 4.  Taste it occasionally until the remaining yeast has enough time to eat it all.  THEN you can chill it back down and enjoy.

In my experience 2-3 days has always been enough.  And I think rather than count on the existing yeast, krausening might be the way to go.

[denny]

I avoided dry hopping for a long time due to oxygen ingress potential.  My solution is to use pellets for dry hopping.  I add them with CO2 flowing into fermenter and remove them using bottom dump valve while under low CO2 pressure.

I just open them fermenter and dump them in.  Haven't had a problem doing that.

[majorvices]

Great stuff everyone - thanks! Sounds like my best bet is to warm up the keg for a couple weeks and see where that lands me. It's already partially carbonated in the keg, can the diacetyl be cleaned up in a pressurized vessel, or should I vent the lid (maybe leaving it open) for part of the cleanup period? Also, since most of the yeast has been removed (though it's still somewhat hazy)would adding another sachet be beneficial? It's sitting at 1.007 and ~7% ABV.

FWIW, I was very gentle and slow in removing the hop bag (from fear of oxidation), but also did not want to leave hops in the beer another week and risk extraction of undesirable 'green-ness'. I am new to the 'dry hop during fermentation', but sounds like I should have just left them in and changed my racking schedule if I was concerned over-extraction.

I don't think you will have much success removing the diacetyl once it is in package. You need active yeast to remove diacetyl. As denny suggested, krausening is probably your best bet to remove it -- or a small active starter. Krasuening does work, unless it is caused by infection.

[gimmeales]

Sounds like a little krausening is in order - will get on that today. Thanks fellas - might be a little while, but will report back!

[RC]

As for why you got diacetyl in the first place, it may be that your fermentation was too vigorous. Vigorous fermentations can be just as problematic as sluggish ones. The yeast rip through the sugars so quickly that they can run out of food and go dormant before they have a chance to clean up their metabolites, leaving a lot of acetolactate and other crap behind. Diacetyl has an extremely low taste threshold. Your previous batches, if done on a similar timeline, may have been right on the edge of sensory perception, and your luck simply ran out with this one.

[redrocker652002]

I avoided dry hopping for a long time due to oxygen ingress potential.  My solution is to use pellets for dry hopping.  I add them with CO2 flowing into fermenter and remove them using bottom dump valve while under low CO2 pressure.

I just open them fermenter and dump them in.  Haven't had a problem doing that.

I am in no way an expert, hell I am not even a novice yet, but I do what Denny says.  I open my fermenter and dump in my dry hops.  Once I am ready to keg, I put the fermenter on the counter, run my hose from the spigot to the bottom of the keg, and open the valve slowly to avoid any splashing or bubbling.  I have a floating dip tube that has worked well so far.  So I am not as concerned about getting some particles in the keg.  Seal, CO2 and in the kegerator with about 10 to 15 psi and about 35 degrees.  Leave it there for a few days, although this time it is going to be a week or two, then taste and adjust the CO2 pressure as needed.  I am only on about my 4th or 5th keg, so please take that for what it is worth.  RR

[Richard]

I avoided dry hopping for a long time due to oxygen ingress potential.  My solution is to use pellets for dry hopping.  I add them with CO2 flowing into fermenter and remove them using bottom dump valve while under low CO2 pressure.

I just open them fermenter and dump them in.  Haven't had a problem doing that.

I am in no way an expert, hell I am not even a novice yet, but I do what Denny says.  I open my fermenter and dump in my dry hops.  Once I am ready to keg, I put the fermenter on the counter, run my hose from the spigot to the bottom of the keg, and open the valve slowly to avoid any splashing or bubbling.  I have a floating dip tube that has worked well so far.  So I am not as concerned about getting some particles in the keg.  Seal, CO2 and in the kegerator with about 10 to 15 psi and about 35 degrees.  Leave it there for a few days, although this time it is going to be a week or two, then taste and adjust the CO2 pressure as needed.  I am only on about my 4th or 5th keg, so please take that for what it is worth.  RR

To minimize oxygen exposure during kegging you should use a completely closed transfer into a completely purged keg. Here is a post from BrewBama on how he does it: https://www.homebrewersassociation.org/forum/index.php?topic=35146.msg442579#msg442579 i do it similarly, but now I purge the keg with fermentation gas.

[kramerog]

After thinking it was a keg sanitization issue the first go-around, brewed another identical batch of cold IPA. Recipe is 100% Bohemian Pils, 13.5oz total hops with 6oz added 4-days into a vigorous and nearly complete fermentation with Saflager 34/70. Raised temps to 68F for 48hrs (87% attenuation). Cold crashed after that (removing the bagged dry hops) for several days before racking onto biofine in a keg for another ~5-days @ 34F. It's about a 2.5 week turn-around time which sounds roughly like what the commercial guys are doing. However, I'm getting hints of buttery-ness already I've gone nuclear on my kegerator lines (short of replacing them), but wondering if recipe, process, or sanitization is the most likely culprit here? (not much lager experience, but have made pretty clean 'quick' lagers in similar timeframes with 34/70)

Hop creep could be an issue for you. Hops have enzymatic activity causing sugars to be slowly released and further fermentation. The solution is the same; you need a long enough diacetyl rest for the hop-induced fermentation to end and all the diacetyl to be eaten up, but it may be a few days longer than you are used to.

[denny]

After thinking it was a keg sanitization issue the first go-around, brewed another identical batch of cold IPA. Recipe is 100% Bohemian Pils, 13.5oz total hops with 6oz added 4-days into a vigorous and nearly complete fermentation with Saflager 34/70. Raised temps to 68F for 48hrs (87% attenuation). Cold crashed after that (removing the bagged dry hops) for several days before racking onto biofine in a keg for another ~5-days @ 34F. It's about a 2.5 week turn-around time which sounds roughly like what the commercial guys are doing. However, I'm getting hints of buttery-ness already I've gone nuclear on my kegerator lines (short of replacing them), but wondering if recipe, process, or sanitization is the most likely culprit here? (not much lager experience, but have made pretty clean 'quick' lagers in similar timeframes with 34/70)

Hop creep could be an issue for you. Hops have enzymatic activity causing sugars to be slowly released and further fermentation. The solution is the same; you need a long enough diacetyl rest for the hop-induced fermentation to end and all the diacetyl to be eaten up, but it may be a few days longer than you are used to.

Have you ever experienced hop creep? I tried to make it happen 3 times to study it and I couldn't get it to happen. I tend to think it's not an issue for homebrewers.