fixing diacetyl in keg?

General Homebrew Discussion
1

I realize this has been posted about a lot so sorry about that. I searched around a bit but thought I would just start a new post.

My last batch has been on carb in the keg at 40F for a week. I had a sample last night and it appears to have diacetyl which is a first for me. I noticed it when kegging but didn’t realize since I have not had any experience with it. It is coming through more in the aroma than the taste and is more butterscotch than popcorn. It isn’t horrible but too much for what I was going for. It covers up the delicate hop profile I was shooting for which is really bugging me…

My plan is to the degass the keg, stir any settled yeast back into suspension, and bring up to 70F for a few days. Is this a good idea? At this point it can’t really hurt anything but I also am not sure if it is worth it and I don’t want to get my hopes up.

2

I don’t know if it will work at all but either way I don’t think you need to degas the keg.

3

That should be fine. Last year I made a Vienna Lager that had a lot of diacetyl. I didn’t degass the keg, but simply warmed it up to about 65-68 for about a week. I was glad I didn’t dump the batch because it turned out great.

4

Thanks guys. The only reason I was going to degas was just in case it fermented any more in the keg. I transferred this one too quickly which I think might explain the diacetyl and a higher than expected FG.

5

It kinda depends on the cause of the diacetyl.  If it’s from an infection there’s not much you can do.  If it’s due to incomplete fermentation, you could try krausening.  I doubt simply warming up the keg and counting on the retained yeast will do much.

6

I think it is incomplete fermentation. I don’t think that it is not an infection but I guess it is too early to tell for sure.

I kind of rushed this batch for no particular reason but didn’t take the steps to ensure it was done. It fermented quickly and the yeast dropped out fast. It finished 4 points higher than expected but I am told this may be due to a proper mash out that I don’t normally do…

7

Agreed.

You didn’t back up beer into your lines recently did you? I had an issue where I did that and there was mold in one of my disconnects and lines that was causing hoppy beers to turn butterscotchy. Finally over that mess. Check your co2 lines and disconnects to be sure.

8

Cleaned my lines while I kegged this batch. I noticed the caramelly, butterscotch notes when I took a hydrometer sample when kegging.

9

Oh, so it’s not a post kegging thing. That’s good. If it’s an ale, it seems doubtful that it’d be a yeast issue. Not many ales produce diacetyl.
I had a friend who bottled a beer, it turned butterscotchy, then went away after a while in bottles. I think it was because the temps changed during fermentation a lot. I guess that’s one benefit to bottling conditioning versus kegging…

10

Diacety remaining from fermentation will age out in the keg over time. If it’s an infection related that’s another issue as Denny noted.

Try waiting it out or krausening to see what happens.

11

Thanks guys! I was under the impression that it would not go away even it was fermentation related.

I used S-04 between 62F - 66F. The last beer I did under similar circumstances ended up super clean which makes me a bit worried about infection. The last time I brewed this particular beer it got some strange infection that made it taste “belgianesque”. If this batch ends up infected, I think it is time to move on from the bad mojo…

12

If you get repeated infection issues, then you should check your sanitizer or routine and finally consider new plastics for whatever touched that batch.  Some bacteria is really persistent.  You can keep the infected plastic stuff for use on sours, perhaps.

13

Well the last batch that was infected was about 6 months ago. I normally don’t run into many infection issues.

14

Curious of the recipe. The description of carmely makes me think it could be grain bill.

15

70% two row
20% light munich
5% flaked oats
5% crystal 40

Mashed at 158 for 75 minutes

Hops:
Magnum 60 min
Amarillo 10 min
Cascade/Citra 0 min

S-04
OG 1.047
FG 1.016
IBUs ~25

this beer is my session beer so it is around 4% ABV. The first version I did of this beer was well balanced but not malty per se. The second batch was infected but I drank it because it tasted like a Belgian…haha.

This one does have some more sweetness due to a higher FG but the butterscotch/toffee character seems out of place. The aroma completely overtakes the cascade/citra flavor and aroma which was quite nice on the first batch.

16

Hard to say without tasting, but some people mistake munich’s melanoidins as diacetyl

17

True. If I hadn’t have made a 100% munich beer then I probably wouldn’t be sure. This 20% munich beer definitely has a butterscotch quality that wasn’t in the 100% munich beer.

18

Don’t fall into the trap of thinking melanoidins are a flavor.

19

It’s color right? But they don’t contribute to flavor?

In any event I used the wrong word. Then I had to figure out where I got that from. BJCP Scottish guide states kettle caramelizing gets mistaken for Diacetyl…my apologies. Product of distance learning and too eager to share what was not fully learned. I’ll keep an eye on that. Stick to what I know, rather than heard.

20

Yep, color, no flavor.  However, some of the sane reactions that form melanoidins will also form flavors.