Diacetyl developing in the keg

[FreddyBrewger]

John Palmer just recently did a webinar that focused heavily on diacetyl. Check it out: https://www.homebrewersassociation.org/archived-zymurgy-live/welcome-golden-age-brewing/

 

[stickyfinger]

John Palmer just recently did a webinar that focused heavily on diacetyl. Check it out: https://www.homebrewersassociation.org/archived-zymurgy-live/welcome-golden-age-brewing/

does he talk about dry hopping and diacetyl? I don't have a membership to listen to it.

 

[FreddyBrewger]

He discusses how diacetyl can rear its ugly head and how diacetyl rests are a good idea for both lagers and ales. He really gets into some chemistry. I'd suggest getting a one year membership because the perks (discounts online, at your LHBS, and all-day happy hour at your local brew pubs) pay for themselves within a month.

 

[stickyfinger]

Sent this question to White Labs:

Hi,

I've been struggling with some IPAs I have made. I've made several in the last year but 3 recent ones have had diacetyl that appeared only after the beer was in the keg for a few days to a few weeks! I've never had this problem, and I've been brewing for years now. I've never used as many dry hops as I have in the last 2 years or so though. Have you heard of people having issues with diacetyl mysteriously appearing in heavily dry hopped beers? Do you have any info. on this? I heard that maybe Kara Taylor had some info on this?


Got this reply from White Labs about diacetyl:

Most common (and we have seen it in our brewery as well), dry hopping can introduce oxygen to the environment causing an increase in diacetyl. You could try dry hopping a little earlier so the yeast has SOME activity to try and consume the oxygen.

Cheers!

I dry hopped pretty early and still got it, but maybe I need to let it rest even longer or something. I wonder if something else isn't going on too though still.

 

[Duffman870727]

I can't find where you've mentioned it, how many days/weeks do you ferment before transferring into kegs? What is your protocol for determining that the beer is ready to package?

Infection based diacetyl would be accompanied by sourness, this is unlikely.

 

[stickyfinger]

I can't find where you've mentioned it, how many days/weeks do you ferment before transferring into kegs? What is your protocol for determining that the beer is ready to package?

Infection based diacetyl would be accompanied by sourness, this is unlikely.

I'm not very precise on when I transfer. Mostly, I make sure the krausen is dropping, dry hop (usually around day 3-5) and then rack to keg around day 10-14. It varies depending on my schedule. I don't do any tests. Yeah, I've heard sourness usually comes with infection. I think diacetyl CAN come without sourness though. It just makes more sense it's something to do with the wort, hops, oxygen and yeast though. I think I'll try a forced diacetyl test before kegging next time.

 

[Duffman870727]

I'm not very precise on when I transfer. Mostly, I make sure the krausen is dropping, dry hop (usually around day 3-5) and then rack to keg around day 10-14. I don't do any tests. Yeah, I've heard sourness usually comes with infection. I think I'll try a forced diacetyl test before kegging next time.

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.

 

[stickyfinger]

I don't think 21-30 days is typical for ales, certainly not for most people i talk to, maybe lagers. The odd thing is that this ONLY happens in beers that have a heavy dry hop. I even make lagers that I drink before 30 days with no issues. I think you might be right that the yeast is having problems with my heavily dry-hopped beers though. It could be mash temp or it could be the dry hop introducing oxygen.

I definitely plan to try a forced diacetyl test. that will at least tell me if I have acetolactate in my beer before i keg.

thanks for the input.

 

[stickyfinger]

Wow! I just did a forced diacetyl test on a sample of my latest IPA. I fermented it with WLP090 for about 4 days at 65F and then ramped it up to 72F and added the dry hops. It's been a total of 13 days since pitching. The forced diacetyl tested yielded a definite existence of diacetyl precursors in my wort still!!! I'm surprised!! Wow. I guess I'll leave it at 74F in my basement for a week while on vacation and test again.

What if it still isn't gone after 24 days in the carboy? Maybe I HAVE been racking my beers too soon. Jesus. I wonder why I haven't had more problems before now though?

 

[stickyfinger]

Just found an interesting review article on diacetyl in beer that has some recommendations for things to try to reduce it, based on a few studies:

http://onlinelibrary.wiley.com/doi/10.1002/jib.84/abstract

Some of the interesting things to try:

-decrease the beer pH - increases speed of the AAL - diacetyl reaction
-increase fermenation temperature - more yeast produced and faster AAl - diacetyl even if there is more diacetyl also produced
-valine supplementation - reduces need for yeast to produce valine and the inevitable diacetyl in the process
-wort FAN at lower levels - results in yeast taking up valine more quickly rather than other more readily available amino acids
-mash in at 122F and then ramp up to encourage valine-rich wort
-pitch less yeast so that fermentation does not end very quickly, resulting in less active yeast by the time AAL forms diacetyl

 

[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!