Diacetyl with all grain, but not extract

[joenearboston]

My extract brews come out great, but all of my all-grains have slight diacetyl (microwave butter aroma) even after two weeks in fermenter. I aerate with pure oxygen for at least a minute. I'm going to let it sit longer, but wanted to see if anyone spots anything that looks wrong with this APA process:

==Grain Bill==
Pale 2 Row (160 oz)
Crystal 10 Malt (8 oz)
Crushed at LHBS, wondering if their crush setting is too fine.
There was about a 1/2 cup of barley flour at the bottom of the plastic bag.

==Water==
Mash: 165F strike, 3 3/4 gallons of RO + 1/4 tsp CaCl + 1/4 tsp Gypsum
Sparge: 158F, 4 gallons of RO + 1/4 tsp CaCl + 1/4 tsp Gypsum

==Mash==
3 and 3/4 gallons at 165F strike
Mash temp measured 151 F after 10 minutes
pH ~ 5.1
45 minutes

==Sparge==
4 gallons at 158F

==Kettle==
1 oz chinook at 60 min
1 oz cascade at 35 min
1 oz cascade at 0 min
Whirlpool 30 minutes

==Ferment==
Plate chiller cool down to 75 F
Aerate with pure oxygen stone for 1 minute
Pitched dry yeast s05, no starter
Bubbling within 24 hours
Ferment at 65F for one week (temp controlled) in a keg
(I ferment in kegs with a slightly bent dip tube so I can maintain a closed system at all times for all transfers)
After one week, I could really smell the diacetyl so I moved the temp up to 71F and let it sit another week. I also roused the yeast by slightly shaking.
After 2nd week, I can still detect diacetyl aroma, but not as much, but it is still there.

I plan to keep waiting another few weeks or so.

 

[joenearboston]

Forgot to mention: I did a batch sparge with recirculation until clear

 

[joenearboston]

Also: My extract process is identical (same yeast, fermentation process) except the mash part of course.

 

[Yooper]

Diacetyl comes from either yeast being stressed/unhealthy or infection.

Some yeast strains produce more diacetyl than others, but most healthy fermentations should be able to clean it up. Which yeast strain are you using, and how big of a starter? Or, how many packages of yeast if not using a starter? And lastly, is this reused yeast or fresh packages?

 

[philber]

Have you gotten and second opinion on the diacetyl. Take a sample into you local HB shop or a brew club.

How many batches have you noticed this on? Have you noticed a film on top of the beer (infection)?

Assuming your kegs were well sanitized with Starsan or PBW? Also assuming you have an airlock on your keg fermenter?

Remember all grain will take a few more weeks in the fermenter and/or bottled to come to its peak.

 

[joenearboston]

Yooper and Philber,

Thanks for your responses.

I am pitching from a single fresh package of 11 gram dry Safale US-05 yeast.

O.G. was about 1.045 for this APA.

I have not noticed any film after pouring.

I clean my fermentation vessel with PBW at 100F followed by Star San with plenty of foam.

I have brewed about 7 all grain batches and noticed the buttery aroma on every single one. I have brewed 3 extract batches without any issues. Process was identical between extract and all-grain except for mash part, of course.

I think you both might be on to something with pitching rate. But, what is it about all-grain that is more stressful on yeast compared to extract for the same original gravity?

Also, I am probably more sensitive to the buttery aroma than most, but it is definitely there. Distinctively an uncooked "microwave popcorn" smell.

Thanks again for the tips!

 

[Yooper]

One package for a 1.045 beer is definitely not underpitching the yeast, so you're good there.

I can't think of anything in the mash that would cause this, so now I'm wondering about infected equipment post-boil. Pediococcus has a diacetyl flavor, so that's my next thought.

Your mash pH is a bit low- I'd rather see it at 5.3 at room temperature- but if anything the beer would taste a bit tart, not like diaceytl.

 

[joenearboston]

Yes, the pH is a little low. I'll need to work on that as well.

I'm going to let it sit another week at 65F and share with the group what I find.

 

[joenearboston]

Just wanted to close the loop - I got this fixed by doing a couple of things:

Keeping on yeast cake for 3 weeks
Pitching at 65F instead of 80F
Using acids to manage pH, using salts (gypsum, calcl) to manage flavor