Diacetyl developing in the keg

[stickyfinger]

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!!!

 

[tjosborne]

I'm experiencing something similar. Following.

 

[Smellyglove]

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!!!

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.

 

[Dcpcooks]

It's either contamination or cold crashing to quickly. Yeast will re-absorb diacetyl during fermentation if you give it enough time.

 

[LarMoeCur]

Edited to delete my brain dead reply. Talking about diacetyl not DMS. I didn't have any coffee this morning!

 

[Smellyglove]

Edited to delete my brain dead reply. Talking about diacetyl not DMS. I didn't have any coffee this morning!

He's talking about diacetyl, not DMS..

 

[LarMoeCur]

Smellyglove, I was hoping no one saw that before I could delete it. I was wrong!

 

[Smellyglove]

Smellyglove, I was hoping no one saw that before I could delete it. I was wrong!

Hehe! I'm faster than my own shadow

 

[stickyfinger]

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.

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.

 

[stickyfinger]

It's either contamination or cold crashing to quickly. Yeast will re-absorb diacetyl during fermentation if you give it enough time.

I wonder if contamination could result in detectable diacetyl after 1-2 days in the keg?

 

[stickyfinger]

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.

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.

 

[JonM]

A Pediococcus infection in the tap lines can create diacetyl. Maybe swap them for some new lines?

 

[stickyfinger]

A Pediococcus infection in the tap lines can create diacetyl. Maybe swap them for some new lines?

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.

 

[stickyfinger]

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.

 

[Smellyglove]

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.

What's the pitching temps and fermentation temps?

 

[stickyfinger]

What's the pitching temps and fermentation temps?

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...

 

[Smellyglove]

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...

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?

 

[stickyfinger]

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?

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.

 

[Smellyglove]

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.

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.

 

[stickyfinger]

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.

 

[Dcpcooks]

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!

 

[Smellyglove]

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.

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.

 

[Smellyglove]

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.

 

[stickyfinger]

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!

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)

 

[oylerck]

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.

 

[stickyfinger]

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.

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.

 

[Dcpcooks]

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.

 

[stickyfinger]

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.

 

[Dcpcooks]

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.

 

[stickyfinger]

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.

yes, i am debating natural carbonation in the keg