Diacetyl developing in the keg

[SpeedYellow]

Not sure it's been mentioned here, but diacetyl can easily get created in the keg. If you have significant precursors in the beer, then the oxygen that gets introduced at kegging lets those turn into diacetyl over the course of a few weeks. I've seen this a couple times with lagers. Good news: both times, I was able to cure the beer by setting the keg on its side (to minimize yeast settling), occasional shaking, and keeping warm (65-70F) for a couple weeks. Adding some active yeast/wort wouldn't hurt.

 

[stickyfinger]

Not sure it's been mentioned here, but diacetyl can easily get created in the keg. If you have significant precursors in the beer, then the oxygen that gets introduced at kegging lets those turn into diacetyl over the course of a few weeks. I've seen this a couple times with lagers. Good news: both times, I was able to cure the beer by setting the keg on its side (to minimize yeast settling), occasional shaking, and keeping warm (65-70F) for a couple weeks. Adding some active yeast/wort wouldn't hurt.

this is almost certainly what has happened in my hoppy beers that have succumb to diacetyl. For some reason, in very hoppy beers, the precursors seem to convert over to diacetyl more slowly and then the yeast was more or less gone or dormant once kegged, so as the precursors turned into diacetyl, there was no way to have it removed. I've tried warming up my kegs of IPA to remove diacetyl and have not enjoyed the finished beer. It could work for a malty beer though.

 

[SpeedYellow]

this is almost certainly what has happened in my hoppy beers that have succumb to diacetyl. For some reason, in very hoppy beers, the precursors seem to convert over to diacetyl more slowly and then the yeast was more or less gone or dormant once kegged, so as the precursors turned into diacetyl, there was no way to have it removed. I've tried warming up my kegs of IPA to remove diacetyl and have not enjoyed the finished beer. It could work for a malty beer though.

I'm not sure why you say it couldn't be removed. To rid the diacetyl in a kegged beer that has little/no yeast, then you can just create a small yeast starter, give it several hours to get active, pop your keg open, pitch the starter, and give it a few weeks. It works!

 

[lupulinaddict]

You said the flavor is butterscotch. Could the flavor be described as carmel?
Also, what happens to your hop character once the flavor changes?

 

[stickyfinger]

I'm not sure why you say it couldn't be removed. To rid the diacetyl in a kegged beer that has little/no yeast, then you can just create a small yeast starter, give it several hours to get active, pop your keg open, pitch the starter, and give it a few weeks. It works!

true, after warming the ipa up for 2 weeks, it will not be great though. i can try it though.

 

[stickyfinger]

You said the flavor is butterscotch. Could the flavor be described as carmel?
Also, what happens to your hop character once the flavor changes?

it's butterscotch - definitely diacetyl. I am very sensitive to it.

The hop character just gets really muddied. It kills the crisp, hoppy character to me with the impression of sweetness and and butterscotch character.

 

[Ben58]

What brand of grain are you using? It may be a bad lot. Modern grain is well modified and should not be prone to this happening. Conversely, you may need to go to a 90 minute boil.

 

[stickyfinger]

What brand of grain are you using? It may be a bad lot. Modern grain is well modified and should not be prone to this happening. Conversely, you may need to go to a 90 minute boil.

i've used great western mostly. i doubt it's the malt. how does that contribute to diacetyl? also, never heard of diacetyl issues due to 60 min boil

 

[mikeroesoft]

I've had similar issues off and on with diacetyl in hoppy/heavily hopped APA/IPA's and not at all with any other style I brew. I am also obsessed with cleaning and sanitizing and based on my success with other styles, I am fairly certain I can rule out contamination. I guess at this point, I know now that diacetyl does in fact form at dry hopping in these beers, but I am at a loss to explain why it doesn't happen all the time if my process is the same or at least very similar. Anyway, I believe it could also be that the yeast may have a more difficult time finishing in cloudier beer. I am going to try priming in the serving keg to see if this helps eliminate diacetyl and reduces oxidization.

 

[stickyfinger]

I've been testing almost every beer I brew now for diacetyl precursors. I have NEVER had diacetyl precursors by day 14 (or less) with beers that I did not dry hop. I often have diacetyl precursors in beers that I dry hop. The only yeast that consistently results in NO diacetyl precursors that I could detect after dry hopping is German Ale Yeast, WY1007. I just tried a new yeast for my most recent IPA and dry hopped really early for me. I dry hopped at 48 hrs after pitching and used WLP051, American Ale V. No diacetyl precursors. I also currently have a Jubelale clone going using WLP002. I tested it at about day 10 and had no diacetyl precursors. Decided to dry hop on day 11, and retested on day 17 and had diacetyl precursors! Dry hopping definitely does/can cause diacetyl precursors. Now, I've had kegs of beer that I knew had diacetyl precursors that sometimes turned to diacetyl and sometimes didn't. Based on my success with WLP051, I think I am going to try dry hopping at 48 hrs into primary from now on and see if that eliminates the problem.

 

[joegbeer]

Thread was an interesting read. In summary, it sounds like the concern is oxygen introduced during dry hopping can contribute to diacetyl. I don't dry hop a lot. I also don't think I'm very sensitive to diacetyl. But I do have two suggestions...

1) Dry Hop at yeast pitch. No oxygen problem. I would think that this would work well if you think primary can be completed in 6 days. I've read some about NEIPA brews using this technique.

2) Dry Hop drop mechanism. Poor man's approach, starsan a muslin bag and a metal disk. Fill with hops. External magnet the hops to the fermenter lid. Pull the magnet on whatever day you want to drop the hops.

 

[stickyfinger]

Thread was an interesting read. In summary, it sounds like the concern is oxygen introduced during dry hopping can contribute to diacetyl. I don't dry hop a lot. I also don't think I'm very sensitive to diacetyl. But I do have two suggestions...

1) Dry Hop at yeast pitch. No oxygen problem. I would think that this would work well if you think primary can be completed in 6 days. I've read some about NEIPA brews using this technique.

2) Dry Hop drop mechanism. Poor man's approach, starsan a muslin bag and a metal disk. Fill with hops. External magnet the hops to the fermenter lid. Pull the magnet on whatever day you want to drop the hops.

It's either sugars from the dry hops(I've heard this postulated in some articles) or oxygen or both that cause the yeast to produce more diacetyl precursors I guess, and then they need time to oxidize before you can rack to keg safely.

I'd have to brew smaller batches if I pitched right at yeast pitch as I don't want hops blowing out of my carboy and clogging things up. That is definitely an option though. With certain low-foam yeasts that could be a good option.

 

[Hwk-I-St8]

With that information, I can say with near certainty that this is simply a fermentation management issue (which is easily fixed, with patience!). 10-14 days is an awfully quick turnaround time for a beer, 21-30 days is what your typical yeast strains will require to finish the beer.

Why we're seeing this more with heavily dry-hopped beers? I'd speculate the conflict of interest in allowing time for the beer to finish and trying to maintain a fresh, hoppy flavor and not leaving dry hops in the fermenter for weeks to avoid the beer becoming "grassy". You want hop oils to be present with active yeast so that bio-conversion gives you the flavors you're expecting from the hops, and hop oils are unlocked from the Beta-Glycosides (sugar + essential oil, broken down by yeast). Anyway, the hopping techniques are a little off topic for the diacetyl issue.

Certainly perform a forced diacetyl test next brew, and try giving it 21 days fermentation before kegging. Test it at 10-14 days, and again at 21 days and compare your notes. Acetolactate (diacetyl precursor) is odorless and flavorless until it breaks down into diacetyl, which it will do over time if any exists in solution in the packaged beer. You can force any acetolactate to convert into diacetyl by heating the sample to 140F-158F for 20 minutes. Compare the forced sample to a regular sample, there will be one of three results:

i) Diacetyl detected in both samples means that beer is not finished fermentation, healthy yeast will have cleaned the beer of all diacetyl when fermentation is complete.
ii) Only heated sample produces diacetyl. This means that fermentation is near completion. The yeast are cleaning up the diacetyl in the beer, but some acetolactate precursor still remains to be broken down and re-uptaken.
iii) Both samples diacetyl negative. All precursor has been broken down, and all diacetyl has been taken up by the yeast. This beer has completed fermentation.

Allowing the temperature to "free-rise" when you're at about 80% attenuation will help the yeast re-uptake the acetaldehyde and diacetyl. The colder you can ferment primary, the more you'll suppress production of these compounds, but yeast are "happiest" at around 80F, so allowing the temp to rise near the end of fermentation removes some stress from the yeast and they will be able to do a better/faster job of cleaning up.

I typically keg my NEIPAs about 7 days after brew. A typical schedule is to dry hop heavily at about 24 hours after pitch. The next day I start raising the temp. After a couple days I cold crash, then keg a couple days after that. I've had kegs last as long as 7 weeks with no signs of diacetyl.

 

[stickyfinger]

some more info. for anyone still interested in my saga or these issues:

Tried a new split batch of IPA using wy1272 vs wy1318, exactly the same in every way except for the yeast. Brewed 1.29.18, dry hopped 2.1.18 with 1.5 oz/gal. on 2.8.18 took a sample from each, no diacetyl but a precursor test resulted in massive amount of precursors. 2.14.18 racked to purged kegs devil be damned and did another force test on both. gravity had dropped some more on both and both had some precursors but probably a lot less than the first time i tested them. 1272 seemed to have a few more precursors than the 1318 batch but hard to be certain.

did several side by sides and had friends do them as well. no one was able to tell them apart flavor wise. also, no one picked up diacetyl. they were in the keg until about 4.1.18 or so when both were kicked. at times i'd drink either one throughout that time and think they were starting to "turn" but they never did and then i couldn't detect diacetyl so not sure if it was just my imagination or if the yeast is able to slowly keep taking care of diacetyl as it is formed even at keezer temps. (these are very hazy beers and must have a good amount of yeast in suspension even after weeks in the keg, though it does slowly drop out eventually.)

I just did three more IPAs over the last couple weeks. On all of them I started fermentation at 64F, dry hopped at 48 hrs, raised temp to 66F after four days and 68F after two more days. I plan to let them all rest at least 12 days or maybe 14 from dry hop day and then test for precursors and keg.

I've been doing a lot of searching for more info on this phenomenon:

Some discussion of "hop creep" - comments too:
https://www.themadfermentationist.com/2018/02/sapwood-cellars-cheater-hops-ne-dipa.html

Somewhat informative discussion of dry hopping and diacetyl:
http://masterbrewerspodcast.com/073-dry-hoppings-correlation-with-diacetyl

I've read some other stuff, but can't remember it all now. Seems like this is becoming more of a problem at commercial breweries though with the high hopping rates in the dry hop. i wonder how the really great NEIPA breweries eliminate the diacetyl issue? It might be interesting to try dry hopping at a cooler temp and see if that helps solve the problem.

I am thinking about trying some keg conditioning or spunding at some point if my current practices don't result in diacetyl-free kegs from now on. Also wondering if I should just dry hop right at yeast pitch or maybe at 24 hrs as someone above talked about. Also have thought about trying the low-DO approach on the cold side and ferment in 5G kegs. Lots to try!