How did I end up with Diacetyl in my IPL

[suitbrewing]

Greetings to the group and happy new brewing year to all!!!



I am trying to understand why I ended up with Diacetyl in my IPL!

The beer

This is a beer with a 90% pilsner malt and 10% carapils mashed at 65c (single infusion) for one hour and boiled for 90 minutes.

OG: 1.052

Fermentation

Fermented using 2 sachets of rehydrated M76. Yeast packs were reasonably fresh.

The wort was aerated for 1:30 minutes using pure oxygen through an aeration stone before pitching.

I pitched @ 9C and let the wort rise to 11c over the first couple of days naturally.

After the first week or so I increased temps to 13-14 to complete attenuation.

Finally the beer spend 4 days at 16c (diacetyl rest).

During the diacetyl rest I added dry hops in a hop sock which were removed using a stainless steel rod 4 days later.

Final gravity was 1.010

The beer was conditioned at 12C for another week and cold crushed at 3c for kegging.

The diacetyl flavor seems to have developed a week after kegging.

Oxygen exposure

My beer was exposed to oxygen at three points in time – Opened fermentor to drop dry hops – Opened fermentor to spoon out dry hops – transfer of been from fermentor to keg using siphon.

The question

All thoughts welcome!!!

Did I leave the diacetyl rest for too late when the yeast was already dormant???

Happy to share more detailed fermentation schedule.

 

[bur]

When you conditioned at 12C was it still on the yeast? Or was it moved off the yeast?

After running into a diacetyl issue with a lager I now do a diacetyl test with them before cold crashing so I have some assurance the yeast are done.

If it’s not a fermentation issue, and honestly it sounds like you have things pretty well controlled and set up, then that leaves oxygen exposure or *possibly* an infection.

To address it you could try krausening, i.e. make a starter and pitch at high krausen into the keg. I’ve never tried this though (modest amounts of diacetyl don’t bother me).

 

[MaxStout]

Looks like your fermentation regimen was ok, so I'm thinking a pedio infection. Replace tubing and give everything else a good cleaning and thorough sanitizing before next brew.

 

[Vale71]

I wouldn't go screaming "infection" yet. A pedio infection takes its time to develop, any diacetyl precursors will on the other hand show up rather quickly. There are lots of factors that can influence diacetyl production, it's impossible to tell which of them (or any combination thereof) is responsible for the high diacetyl levels in your beer.
Your best bet now is to give the beer time and see if the yeast clears it up to the point it's no longer detectable.

 

[suitbrewing]

When you conditioned at 12C was it still on the yeast? Or was it moved off the yeast?

The beer was kept on the yeast until kegging.

I am wondering whether my heroics with dry hopping could have caused the issues. I was aiming for no unnecessary moving around of the wort (to minimize oxidation), no green taste (hence 4 days of dry hopping) and cold crush before transferring to the keg. That's why I decided to add the hops in primary and then remove them before cold crushing.

The beer is currently in my keezer @ 2c. I assume I will need to let it warm up if the yeast would have any chance to "eat up" the diacetyl? Its also under pressure! does it matter

 

[Coffeeturnal]

To address it you could try krausening, i.e. make a starter and pitch at high krausen into the keg. I’ve never tried this though (modest amounts of diacetyl don’t bother me).

I recommend doing this. I did it recently with a batch that had ridiculous levels of diacetyl and it fixed it completely. I just used US-05.

I assume you would need to warm it up for this to work.

 

[suitbrewing]

Do you mean to prepare a starter with US-05 (or equivalent) or to simply add rehydrated US-05 ??

Anyone who has gone through this process before feel free to fix the below process for me:

• Warm up and depressurise keg
  
  
• Open keg add yeast (starter??/ rehydrated dry yeast??)
  
  
• Re seal keg ??? (or add airlock to keg???)
  
  
• Keep warm for 2 weeks (or keep warm for 4 weeks???)
  
  
• Re chill and carbonate beer
  
  
• Enjoy diacetyl free IPL ;-)
  

 

[suitbrewing]

Btw, this is why I love this hobby!!!! (well and the fact that you get to produce your own beer)

I am into other hobbies (coffee roasting, classic bicycles, break baking…) and I can say without any shadow of a doubt that no other community either through digital means or face to face interaction, comes close to homebrewers in terms of sharing knowledge and supporting each other!!!

 

[Coffeeturnal]

Do you mean to prepare a starter with US-05 (or equivalent) or to simply add rehydrated US-05 ??

Anyone who has gone through this process before feel free to fix the below process for me:

• Warm up and depressurise keg
  
  
• Open keg add yeast (starter??/ rehydrated dry yeast??)
  
  
• Re seal keg ??? (or add airlock to keg???)
  
  
• Keep warm for 2 weeks (or keep warm for 4 weeks???)
  
  
• Re chill and carbonate beer
  
  
• Enjoy diacetyl free IPL ;-)
  

I don't keg, so I can't comment on the pressure part.

When I fixed my batch it was still in primary (had been there for 2 months for bulk aging). I made a vitality starter with the US-05. I'm not sure if that was necessary, but it worked.

The keg should be warmed to ensure that the yeast doesn't just go to sleep and fall out.

The problem will probably take care of itself in less than a week. My issue was fixed in ~2-3 days. Do a forced diacetyl test before cooling the keg back down.


One potential issue is if US-05 is more attenuative than the lager yeast you used. It could drop your FG. If you think the yeast you used could clean up after itself, you could also pitch a starter of the lager yeast you used in order to prevent more attenuation.

I like US-05 because it's cheap and I know it will clean up, but you should keep in mind what kind of results you want.

 

[SoCal-Doug]

16C (60.8F) is not high enough for a diacetyl rest.

1. There must be live yeast to clean it up. Start your d-rest at 80% to 90% of the expected FG
2. Raise the temp to greater than 65F for 2 to 3 days. I typically set it to 67F

 

[brewcat]

Yeast strain? If it isn't infected then it needed longer to mature. I probably would have gone a couple weeks at 11c. Then raised temps to 20c for the diacetyl rest.

 

[suitbrewing]

 

[suitbrewing]

Now I am home so I cam be more precise with the actual temps.

Above is the fermentation schedule if it makes sense.

After 28/12 I did a cold crush which I did not document.

My diacetyl rest was up to 17c

The yeast strain was Mangroves M76 (Bavarian Lager)

 

[couchsending]

I never do a diacetyl rest for lagers and have never had diacetyl in a finished beer. Pitch more yeast and ferment it colder. You’ll never get diacetyl.

 

[SoCal-Doug]

I never do a diacetyl rest for lagers and have never had diacetyl in a finished beer. Pitch more yeast and ferment it colder. You’ll never get diacetyl.

^^^ Only applies to certain yeast strains. Some strains will generate butter bombs at 40F and 4X the pitch. Research your yeast and adjust your methods accordingly.

 

[SanPancho]

Not to mention heavy dry hopping can lead to it as well.

 

[couchsending]

^^^ Only applies to certain yeast strains. Some strains will generate butter bombs at 40F and 4X the pitch. Research your yeast and adjust your methods accordingly.

What yeast ferments at 40

Yes Czech lager yeast might benefit from fermenting slightly warmer, as well as Augustiner.

Most German Lager yeasts however have the ability to consume diacetyl down to what 37*.

 

[bur]

Do you mean to prepare a starter with US-05 (or equivalent) or to simply add rehydrated US-05 ??

Anyone who has gone through this process before feel free to fix the below process for me:

• Warm up and depressurise keg
  
  
• Open keg add yeast (starter??/ rehydrated dry yeast??)
  
  
• Re seal keg ??? (or add airlock to keg???)
  
  
• Keep warm for 2 weeks (or keep warm for 4 weeks???)
  
  
• Re chill and carbonate beer
  
  
• Enjoy diacetyl free IPL ;-)

This should work. Note you must add the starter at/near the peak of fermentation. This is more than just rehydrating dry yeast, you need to ferment it in a 1-2L starter of 1.035-1.040 wort. You want the yeast to be very active when you pitch it in. Once the starter is really rolling, dump it right into your depressurized, warmed up keg (~20C). Then put the lid back on and maybe re-pressurize a tiny bit to 1-2 psi, just so you know it's sealed. Let it sit warm (20C) for several days and then pull a sample and do a diacetyl test to check on it. I *think* this should take a week at most (granted I've never tried it!). But test it to be sure prior to cold crashing.