Diacetyl developing in the keg

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stickyfinger

stickyfinger

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Hey all,

I have stumbled upon a serious problem with diacetyl that I am going to need to address. It has happened 3 times in the last few months, and I've brewed beers in between these ones that taste fine. Here are some of the things I've noticed when it happened lately:

- All were mashed at 165-167F with mashout (yes I know it is a ridiculously high mash temp, but I have been playing with that on many beers now with no diacetyl)
- Two were using repitched yeast that I had harvested from previous starters
- One was a build up of a fresh pack of yeast
- Yeasts used were WLP002, WY1056 and OYL-057 (hothead)
- The batch using OYL-057 was a split batch - half was soured with lacto and then pitched with OYL-057 three days and did not show any diacetyl compared with the half that was pitched with OYL-057 directly
- All were whirlpooled for at least 15 minutes to sanitize transfer lines, etc.
- All were oxygenated with pure O2
- Good temp control on all batches within yeast recommended range
- Two used the same lot of Citra but one used completely different hops
- All were fermented using pitching rates from mrmalty calculator
- All were dry hopped
- I dry hop by adding pellets to the primary once krausen is subsiding and leave them in about 5-7 days usually
- All were cold crashed after fermentation to drop hops and some yeast
- All tasted great while transferring to the keg
- Transfer was with a racking cane into the out QD on the keg
- Kegs were all filled with Star San completely and then CO2 used to push it out before racking.
- Used a new racking cane on one of them - older racking cane on others
- Diacetyl has showed up in the keg as little as 48 hrs after kegging to 1-2 weeks after kegging
- Warmed up one of the diacetyl batches for 10 days and rechilled - diacetyl was gone and then reappeared again after a couple weeks in the keg cold
- Diacetyl has never shown up in a beer I haven't dry hopped
- I'm pretty sure it's happened with two different cylinders of CO2 connected to the system from different suppliers.


I checked my ball valves on my brew kettle and pump and found that they had some brown scum on them - probably need to start cleaning them every few batches at least. I plan to clean them thoroughly and then pump cleaner through the system before next brew.

I will boil my racking tubing next time, as it is silicone.

I'll also replace my CO2 line for carbonating.

I am wondering if I should dump all of my yeast stores and just use a fresh pack for the next brew.

Anyone else experience this? What else should I do to try to get rid of this? It's very frustrating!!!
 
stickyfinger said:
Hey all,

I have stumbled upon a serious problem with diacetyl that I am going to need to address. It has happened 3 times in the last few months, and I've brewed beers in between these ones that taste fine. Here are some of the things I've noticed when it happened lately:

- All were mashed at 165-167F with mashout (yes I know it is a ridiculously high mash temp, but I have been playing with that on many beers now with no diacetyl)
- Two were using repitched yeast that I had harvested from previous starters
- One was a build up of a fresh pack of yeast
- Yeasts used were WLP002, WY1056 and OYL-057 (hothead)
- The batch using OYL-057 was a split batch - half was soured with lacto and then pitched with OYL-057 three days and did not show any diacetyl compared with the half that was pitched with OYL-057 directly
- All were whirlpooled for at least 15 minutes to sanitize transfer lines, etc.
- All were oxygenated with pure O2
- Good temp control on all batches within yeast recommended range
- Two used the same lot of Citra but one used completely different hops
- All were fermented using pitching rates from mrmalty calculator
- All were dry hopped
- I dry hop by adding pellets to the primary once krausen is subsiding and leave them in about 5-7 days usually
- All were cold crashed after fermentation to drop hops and some yeast
- All tasted great while transferring to the keg
- Transfer was with a racking cane into the out QD on the keg
- Kegs were all filled with Star San completely and then CO2 used to push it out before racking.
- Used a new racking cane on one of them - older racking cane on others
- Diacetyl has showed up in the keg as little as 48 hrs after kegging to 1-2 weeks after kegging
- Warmed up one of the diacetyl batches for 10 days and rechilled - diacetyl was gone and then reappeared again after a couple weeks in the keg cold
- Diacetyl has never shown up in a beer I haven't dry hopped
- I'm pretty sure it's happened with two different cylinders of CO2 connected to the system from different suppliers.


I checked my ball valves on my brew kettle and pump and found that they had some brown scum on them - probably need to start cleaning them every few batches at least. I plan to clean them thoroughly and then pump cleaner through the system before next brew.

I will boil my racking tubing next time, as it is silicone.

I'll also replace my CO2 line for carbonating.

I am wondering if I should dump all of my yeast stores and just use a fresh pack for the next brew.

Anyone else experience this? What else should I do to try to get rid of this? It's very frustrating!!!
Click to expand...

Pitching temps and fermentation temperature regime is also of essence. When you say cold crashed "after fermentation", when is this, as soon as you've reached a stable FG? Like day six-ish?
What temps do you keep your kegs at?

You should maybe start to pull wort samples when you transfer to fermentation, as diacetyl also can be induced by contamination. Don't do anything to the samples, just let it sit in a tight container and see if something starts to grow.
 
It's either contamination or cold crashing to quickly. Yeast will re-absorb diacetyl during fermentation if you give it enough time.
 
Edited to delete my brain dead reply. Talking about diacetyl not DMS. I didn't have any coffee this morning!
 
Smellyglove said:
Pitching temps and fermentation temperature regime is also of essence. When you say cold crashed "after fermentation", when is this, as soon as you've reached a stable FG? Like day six-ish?
What temps do you keep your kegs at?

You should maybe start to pull wort samples when you transfer to fermentation, as diacetyl also can be induced by contamination. Don't do anything to the samples, just let it sit in a tight container and see if something starts to grow.
Click to expand...

I don't usually cold crash until about day 10. I crashed on like day 6 on an IPA recently that did not develop the diacetyl, ironically. I store my kegs at about 37F.

I think you are right about samples. I should collect some samples from the kettle, and I should also take a sample from the primary before cold crashing and heat it up to see if any of the diacetyl precursors are still around at that point.
 
Smellyglove said:
Pitching temps and fermentation temperature regime is also of essence. When you say cold crashed "after fermentation", when is this, as soon as you've reached a stable FG? Like day six-ish?
What temps do you keep your kegs at?

You should maybe start to pull wort samples when you transfer to fermentation, as diacetyl also can be induced by contamination. Don't do anything to the samples, just let it sit in a tight container and see if something starts to grow.
Click to expand...

I forgot to say that I am wondering about my starter and pitching now. It's possible that my starter wort got pretty warm on the stirplate and then when I pitched into my wort, it was warm enough that petite mutants formed. I assumed that as long as I didn't taste diacetyl at kegging that this would not be the explanation though, as petite mutants can't metabolize diacetyl, but I don't think they produce diacetyl.
 
A Pediococcus infection in the tap lines can create diacetyl. Maybe swap them for some new lines?
 
JonM said:
A Pediococcus infection in the tap lines can create diacetyl. Maybe swap them for some new lines?
Click to expand...

I'll certainly throw out the line that is on there now. However, I believe at least one of the brews developed diacetyl without a tap connected to it.
 
Doesn't pedio take a couple months to produce diacetyl and then it is accompanied by sourness? I don't have sourness, and the diacetyl comes sooner. Maybe that makes it more likely to be diacetyl precursors in the wort that are quickly or slowly converting to diacetyl? the cold yeast in the keg wouldn't be able to remove the diacetyl very well most likely. it's hard to say without more information unfortunately.
 
stickyfinger said:
I forgot to say that I am wondering about my starter and pitching now. It's possible that my starter wort got pretty warm on the stirplate and then when I pitched into my wort, it was warm enough that petite mutants formed. I assumed that as long as I didn't taste diacetyl at kegging that this would not be the explanation though, as petite mutants can't metabolize diacetyl, but I don't think they produce diacetyl.
Click to expand...

What's the pitching temps and fermentation temps?
 
Smellyglove said:
What's the pitching temps and fermentation temps?
Click to expand...

All of the beers with diacetyl were pitched and fermented at 67 or 68F with one degree of hystersis (temp controller probe taped to side of carboy and insulated.)

i don't know how warm the yeast starter was though...
 
stickyfinger said:
All of the beers with diacetyl were pitched and fermented at 67 or 68F with one degree of hystersis (temp controller probe taped to side of carboy and insulated.)

i don't know how warm the yeast starter was though...
Click to expand...

Then I'd say that you can rule fermentation temps out of the equation and focus elsewhere.

Might sound like a stupid question. Are you sure its Diacetyl?
 
Smellyglove said:
Then I'd say that you can rule fermentation temps out of the equation and focus elsewhere.

Might sound like a stupid question. Are you sure its Diacetyl?
Click to expand...

Yeah, my fermentations are locked in that way, and I thought my sanitization was. It's also confusing (though maybe a red herring) that I haven't had this problem with any beers that were not dry hopped.

I'm also starting to wonder if there is something with my high mash temps with dry hopping that is causing this. I plan to stop mashing high for awhile and go back to 155F as my standard mash temp. I have to try all sorts of stuff to knock this diacetyl back. It ruins beer!

I am not sure it is diacetyl in a chemical sense, as I haven't put it through a GCMS, but I am very confident that it is diacetyl. It tastes like butterscotch to me. I am pretty sensitive to it I think, as I have tasted it in some beers that others can't, but several people confirmed strong diacetyl in at least one of the batches I did.
 
stickyfinger said:
Yeah, my fermentations are locked in that way, and I thought my sanitization was. It's also confusing (though maybe a red herring) that I haven't had this problem with any beers that were not dry hopped.

I'm also starting to wonder if there is something with my high mash temps with dry hopping that is causing this. I plan to stop mashing high for awhile and go back to 155F as my standard mash temp. I have to try all sorts of stuff to knock this diacetyl back. It ruins beer!

I am not sure it is diacetyl in a chemical sense, as I haven't put it through a GCMS, but I am very confident that it is diacetyl. It tastes like butterscotch to me. I am pretty sensitive to it I think, as I have tasted it in some beers that others can't, but several people confirmed strong diacetyl in at least one of the batches I did.
Click to expand...

For what it's worth. A buddy of mine has very high attenuation in his setup, so he can mash some of his beers close to 70C, and also, he has an extreme sense for diacetyl, like ridiculously low threshold for diacetyl (poor bastard), and he also dryhops, not much, but for just a little ompf, he makes mostly english and german style beers.

But. I'd clean the valves, hoses and stuff which comes in contact with the beer at and after transfering to fermentor, and burn the beer-lines and swap them with new ones. If you have a bug in a beer-line it can work it's way back into the keg.
 
This is an interesting read for anyone looking into diacetyl: I thought the comments at near the end of the article had a couple interesting stories about diacetyl in dry hopped beer:

https://beersensoryscience.wordpress.com/2010/11/18/diacetyl-1/#comment-3015

I posted the last comment on the thread. I really haven't had this problem until I started dry hopping with very large amounts, like 2 oz/gal. I plan to drop that back and see if that does anything as well, seems crazy, but it's possible. I've heard of professional brewers having problems with US-05 and dry hopping for diacetyl production as well.
 
Are you using lactic acid to acidify the wort? It may be a long shot but I thought I'd ask. The spoilage bacteria that can produce diacetyl are from the lactic acid family. That bacteria can impact beer in post fermentation storage. While I don't agree with a mash temp at 167 I doubt that's the cause of the problem.

I would do a deep clean on the kegs, and change out gaskets, beer lines and connects. I'd do this first as it sounds like this is all happening post fermentation and that's suggestive of bacterial infection. It easy to rule that out with a deep clean.
Secondarily I'd give your beers a few days longer on the yeast. It's an easy test to rule that out of your process. Three days at terminal gravity should be enough.

Lastly I'd look at how your collecting yeast for re use. Is it possible your selecting the most flocculant yeast? Could you be putting some selective pressure on the yeast at some point? If the other suggestions don't fix it then your yeast is a good place to look.

I think an infection could cause the off flavor relatively quickly so if it were me I'd start with the kegs!

Cheers!
 
stickyfinger said:
This is an interesting read for anyone looking into diacetyl: I thought the comments at near the end of the article had a couple interesting stories about diacetyl in dry hopped beer:

https://beersensoryscience.wordpress.com/2010/11/18/diacetyl-1/#comment-3015

I posted the last comment on the thread. I really haven't had this problem until I started dry hopping with very large amounts, like 2 oz/gal. I plan to drop that back and see if that does anything as well, seems crazy, but it's possible. I've heard of professional brewers having problems with US-05 and dry hopping for diacetyl production as well.
Click to expand...

Great link. After reading that I'm glad I jumped aboard this thread. As a matter of fact, I think I've also had some D in my heavily hopped beers. But as far as I remember it's been with 007, british. I remember I've sat there having a first sip and going "D?" but after a glass or two I didn't notice it anymore, probably because of numbing and that I've gotten used to the taste.
 
Not editing post since maybe TS would miss it. Regarding my buddy I wrote about above. He doesn't use nutes in his starters, only main wort, as he somewhere has sniffed out that this can cause D.
 
Dcpcooks said:
Are you using lactic acid to acidify the wort? It may be a long shot but I thought I'd ask. The spoilage bacteria that can produce diacetyl are from the lactic acid family. That bacteria can impact beer in post fermentation storage. While I don't agree with a mash temp at 167 I doubt that's the cause of the problem.

I would do a deep clean on the kegs, and change out gaskets, beer lines and connects. I'd do this first as it sounds like this is all happening post fermentation and that's suggestive of bacterial infection. It easy to rule that out with a deep clean.
Secondarily I'd give your beers a few days longer on the yeast. It's an easy test to rule that out of your process. Three days at terminal gravity should be enough.

Lastly I'd look at how your collecting yeast for re use. Is it possible your selecting the most flocculant yeast? Could you be putting some selective pressure on the yeast at some point? If the other suggestions don't fix it then your yeast is a good place to look.

I think an infection could cause the off flavor relatively quickly so if it were me I'd start with the kegs!

Cheers!
Click to expand...

I just started with lacto and have only used it on one batch. It was the OYL blend that is supposed to be completely hindered by any IBUs. I don't think I've used it enough yet for it to have spread throughout the brewery. I was wondering about it though. Honestly, my entire brewery (basement) is likely covered with natural lactobacillus from all of the malt i mill down there!!! I can't believe I didn't have this problem years ago if it were due to lactobacillus.

I completely disassemble my kegs after each use and soak all parts in sodium percarbonate. I think they are pretty clean. I'll boost my sodium percarbonate next time though. I usually take apart the QD and faucet on the draft lines each brew and soak all parts as well.

I plan to give the beer some more time on the yeast as well.

I don't select for anything in my yeast harvesting, as I make a large starter and harvest from that. So, unless my conditions in my starter are more favorable to certain yeast cells, it should be very similar to what comes from the yeast company.

I also re-use my star san, as I make it from ultrapure water, but i have been doing that for probably 13 yrs now. I don't think that is it. i read you can make it a lot stronger than recommended though with no ill effects, so maybe i'll start making it at 125% recommended to account for the times I dip wet objects into the sanitizer (thus diluting it some)
 
Where do you dry hop and at what stage? I have never experienced diacetyl, but I have oxidized my beer when dry hopping. So I started dryhopping in a keg and the pushing the beer to a new keg.

I must say that I have transfer at 6 days many times and all of my IPAs turn out fine with us-05.

Just curious, not sure if oxidation has been ruled out.
 
oylerck said:
Where do you dry hop and at what stage? I have never experienced diacetyl, but I have oxidized my beer when dry hopping. So I started dryhopping in a keg and the pushing the beer to a new keg.

I must say that I have transfer at 6 days many times and all of my IPAs turn out fine with us-05.

Just curious, not sure if oxidation has been ruled out.
Click to expand...

I dry hop only in primary, usually right after the krausen starts dropping, anywhere from day 2 - 5 depending on the beer. The hops stay in 6-9 days usually, as I usually cold crash and then rack to purged keg on day 10-11.

I certainly introduce oxygen, but I think the yeast are getting rid of a lot of it. When I don't get diacetyl, the beers stay hoppy for several weeks.
 
I was just looking at the Pliny thread and some folks are having this problem with heavily dry hoped IPA's. Diacetyl is developing in the keg on heavily dry hopped beers. They even posted a link to pro brewers site that talks about the challenge, it's a ten year old thread. So it seems this is a thing. You learn something new every day.
 
It might be possible that this issue hasn't come up as frequently in the past b/c we are pushing the level of dry hopping higher and higher these days.
 
I agree with that. We are pushing hop usage to new levels all the time. I suspect it's related to temps and timing of dry hoping. My gut tells me to dry hop with a few gravity points left in primary and then bump the temp up a bit. This will allow the yeast to scavenge any o2 introduced with the hops. It will also serve as a d rest simultaneously.

Warm keg conditioning could also help reduce the problem as it would allow the yeast still in suspension to keep working to reabsorb the precursors.
 
Dcpcooks said:
I agree with that. We are pushing hop usage to new levels all the time. I suspect it's related to temps and timing of dry hoping. My gut tells me to dry hop with a few gravity points left in primary and then bump the temp up a bit. This will allow the yeast to scavenge any o2 introduced with the hops. It will also serve as a d rest simultaneously.

Warm keg conditioning could also help reduce the problem as it would allow the yeast still in suspension to keep working to reabsorb the precursors.
Click to expand...


yes, i am debating natural carbonation in the keg
 
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.
 
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.
 
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.
 
Duffman870727 said:
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.
Click to expand...

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.
 
stickyfinger said:
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.
Click to expand...

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 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.
 
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?
 
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
 

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