Diacetyl or bug - Butterscotch off flavor

[Moose_MI]

Brewed a 10Gal IPA. Split into 2 fermenters ...
Fermentor #1 - repitched a 2 week old 1056 slurry that came from a light cream ale...no starter. Still drinking that cream ale..really good. Had a solid 48hr lag time which is unusual for me but i do not pitch slurries often.
Fermenter #2 - wlp400 Belgian wit slurry...3 week old...no starter. Probably 16hr lag. The belgian blonde it came from is also really good.

After 2 weeks gravity was good on both .. 1.011...tasted good..no off flavors.
Dry hopped for a week. I always boil my hop bags 2X before they go in my beer.

After 1 week I cracked the 1056 fermenter and immediately noticed butterscotch smell.....damn it. The wlp400 does not have this at all.

My question...if the butterscotch is diacetyl from fermentation issues should I have been able to pick that up when i sampled prior to dry hopping?

I’m trying to figure out if i had a fermentation issue or a bug. I’ve had this butterscotch thing happen to me a few times over the last couple years. Not common..but it has happened before. Trying to figure out where I’m getting it and i am an epic failure at taking notes

 

[Moose_MI]

Anyone?

 

[muledogus]

Is it still at fermentation temp? If so it should have had plenty time to clean up but could possibly still take more time if it were a fermentation issue. Pitching some new, healthy yeast on it should help clean it up a little if that were the case, though. Probably worth trying instead of dumping.

 

[Moose_MI]

Have no plans to dump.
At 2 weeks there was no butterscotch smell or taste....after a week of dry hop it showed up.
I’m not worried about improving this batch...I’m trying to figure out if this is a bug or fermentation issue

 

[JimRausch]

The AHA posted a thread on Krausening yesterday, which was a copy of an old thread. Just thought of it because one of the indications is to clean up off-flavors like diacetyl. Basically, you are adding some freshly fermenting beer at high krausen stage. As muledogus states above, might be worth giving it a try.

 

[JimRausch]

And to answer your Q about incomplete fermentation vs. contamination, if reinvigorating the fermentation doesn't work, then it's more likely a bug of some sort. What kind? And how do you avoid it in the future? Can't tell unless you plate it and try to grow it out. Or send a sample somewhere that can do that.

 

[Shawn3997]

You must have oxidized the beer a bit when you dry hopped it. The oxygen creates diacetyl. It will go away with some more time on the yeast. I had a batch that I was ready to toss but it cleared up 100% after a few weeks.

 

[Moose_MI]

Thanks for the replies everyone. Ive got this stuff kegged and carb’d so I don’t think I’m going to add yeast to see if it cleans up. I want to say on at least 1 other occasion i had this happen that it did eventually fade but i cant recall for sure.
The other half of this batch still has zero butter to it and infections have never been an issue for me. I keep thinking this was fermentation issue just cant figure why I didn’t perceive it at 2 weeks prior to dry hopping.

Will update as beer conditions to see if it fades

Thanks again

 

[Qhrumphf]

Sometimes certain hop varietals when dry hopped can restart fermentation slightly, not necessarily enough to change gravity, but enough to produce diacetyl precursors. Some varietals I'll dry hop 3 days and crash. Others I leave at ferm temp a week and do a force VDK test before crashing. With time it may be just fine.

 

[muledogus]

In that case just keep the keg room temp for a couple of weeks and try it again.

 

[Shawn3997]

Thanks for the replies everyone. Ive got this stuff kegged and carb’d so I don’t think I’m going to add yeast to see if it cleans up. I want to say on at least 1 other occasion i had this happen that it did eventually fade but i cant recall for sure.
The other half of this batch still has zero butter to it and infections have never been an issue for me. I keep thinking this was fermentation issue just cant figure why I didn’t perceive it at 2 weeks prior to dry hopping.

Will update as beer conditions to see if it fades

Thanks again

Unless you filter it out there is probably enough yeast left to clean up. Let it sit and check it every week or two to see. Mine cleared out in 2 weeks.

 

[Qhrumphf]

You want to make sure not just the diacetyl itself is gone, but the precursors as well. In the issue I posted above, I've noticed diacetyl come out with age as existing precursors oxidize into diacetyl. The force test (heating sample to 160 and holding, then chilling to same temp as unheated control and comparing) quickly oxidizes any precursor to diacetyl and makes it readily apparent. It's a common pro brewing sensory QC check done in absence of (or alongside) lab analytics.

 

[Miraculix]

You want to make sure not just the diacetyl itself is gone, but the precursors as well. In the issue I posted above, I've noticed diacetyl come out with age as existing precursors oxidize into diacetyl. The force test (heating sample to 160 and holding, then chilling to same temp as unheated control and comparing) quickly oxidizes any precursor to diacetyl and makes it readily apparent. It's a common pro brewing sensory QC check done in absence of (or alongside) lab analytics.

Never heard of this, sounds reasonable!

How long do you need to hold it at 160?

 

[Qhrumphf]

Never heard of this, sounds reasonable!

How long do you need to hold it at 160?

10-15 mins should be plenty.

 

[Moose_MI]

Just went back and forth between the 1056 butter neipa beer and wlp400 belgian neipa beer...

Butter still there on 1056 but no worse...been in kegerator so I’ve not followed any suggestions to warm up yet. With some encouragement from community I may just pull this thing from keeper while I’m out of town for a couple days..??

The most interesting thing is that the wlp400 has that neipa cloudiness ...1056 is clear (relataively)...

Cheers!

 

[Moose_MI]

I pulled the keg out and let it sit about 10 days...it improved noticeably. There’s still butter but it’s diminished.

If it was a bug I would have expected it to get worse. The fact it got a little better makes me think it is diacetyl.

And the butter wasn’t there after 2week fermentation but showed up after 1 week of dry hop.

 

[Miraculix]

I pulled the keg out and let it sit about 10 days...it improved noticeably. There’s still butter but it’s diminished.

If it was a bug I would have expected it to get worse. The fact it got a little better makes me think it is diacetyl.

And the butter wasn’t there after 2week fermentation but showed up after 1 week of dry hop.

Fits perfectly with what Qrhumphf said above. Dry hoping can convert some residual sugars into fermentable sugars and restart fermentation a little bit.

 

[Moose_MI]

Agree...mind blown...

I will remember this next time and just remove dry hop bags and let it sit in fermenter until butter goes away and then keg.

Thanks all

 

[Moose_MI]

Hey...wait a minute...I used same dry hops in both beers. If the dry hop is to blame then it still doesn’t explain why only butter in 1 of the fermenters.
Could the sluggish yeast that had more lag time resulted in more precursors that turned into butter when i dry hopped?

Still searching for the answer....

 

[bleme]

A few years ago a guy in my club brewed a 15 gallon batch, fermenting 5 gallons each with wlp001, wy1056, and US-05. Tasting side-by-side, the only difference I could perceive was strong butter in the wy1056. However, half the club couldn't taste any difference at all.

 

[Moose_MI]

Ive used 1056 a good bit and can say for certain that butter is not an expected characteristic. Maybe 1056 is more proned to that off flavor when things are not otherwise happy...like in my case the yeast was a 2/3 week old slurry re-pitch w/o starter...
1056 yeast good....butter bad...