Possible stuck fermentation?

[dj zlim]

TLDR - Made an altbier, and my FG is too high. Is this a mash or fermenting problem, or something else?

I made an altbier a few weeks back, and am now 2 weeks into fermentation. The OG was 1.050, and my FG readings (4 days apart) is at 1.019...giving attenuation at 62%, but I was expecting around 75% (desired FG ~1.012). I'm using an Anvil Foundry on 120V. Here's the recipe and schedule:

Recipe

Distilled Water	Grain	Hops	Yeast
6 gal strike	6lb German Munich	1 oz Perle (60 min)	White Labs WLP029 *
2 gal sparge	3lb German Pilsner	0.5 oz Perle (30 min)	* made with 1L starter 2 days before
	0.75 lb Weyermann Caramunich II	1 oz Hersbrucker (15 min)	(ideal 65 - 69 F)
	2 oz German Carafa I		(expected attenuation 75% +/-3)

I added minerals to create a water profile using Brewer's Friend. I separated out mineral additions for the strike and sparge to get the same profile:

Ca 2+	99.6 ml/L
Mg 2+	15.0 mg/L
Na +	43.8 mg/L
Cl -	95.7 mg/L
SO2 -	77.6 mg/L
Alkalinity	192 mg/L as CaCO3
Residual Alkalinity	112 mg/L as CaCO3

Schedule

Step	Actual Time	Temp	pH	SG
Strike			5.9	1
Strike (with minerals)		127 F	7.9	1
Protein Rest	22 min	122 F	5.5
Beta-Sacch Rest	55 min	149 F	5.5	1.046
Alpha-Sacch Rest	35 min	158 F	5.4	1.058
Mashout	11 min	170 F		1.059
Sparge (pre-boil)		~180 F (sparge)	5.5	1.047
Boil	60 min	212 F
In Fermenter, Pitching Yeast	5 days	66 - 68 F	5.3	1.050 (OG)
Diacetyl Rest	8 days	70 F	4.7	1.019
Today		70 F	4.7	1.019 (FG?)

Halfway through the diacetyl rest, I checked the gravity. It was reading higher than expected, so I pitched another yeast pack without the starter. 4 days later (today), seems like that did nothing. I think I've reached my FG, so I'm planning on starting to lager it for a few weeks next.

Any ideas on what might have happened? I thought it could be in the mash schedule, or perhaps under pitching the yeast. Besides all that, any thoughts on what would make this recipe better? Thanks in advance!

 

[VikeMan]

I agree that this batch should attenuate much more than it has. How confident are you in your mash temps, i.e. how confident are you that you actually hit them?

 

[palmtrees]

If you want to try and get it unstuck, Jamil and John Palmer just did an episode of Brew Strong about stuck fermentation that I found really valuable. Often just adding more yeast won't do much because there is some sort of issue that prevented your current yeast from finishing up, whether that's some unfermentable sugars or more likely a nutrient deficiency. You're also dealing with the fact that you're pitching into an alcoholic environment, which makes it tough for yeast to get going.

I'm dealing with a stuck fermentation right now, too (also stopped at 1.020). I am currently building up a yeast starter with extra yeast nutrient. I plan to pitch at high krausen and hope they have enough gas in the tank to get down another tenth of a point. Though I can't speak to its effectiveness yet, maybe try that? Or you could just toss in some boiled yeast nutrient and try to goose the yeast that's left.

 

[Miraculix]

If you want to try and get it unstuck, Jamil and John Palmer just did an episode of Brew Strong about stuck fermentation that I found really valuable. Often just adding more yeast won't do much because there is some sort of issue that prevented your current yeast from finishing up, whether that's some unfermentable sugars or more likely a nutrient deficiency. You're also dealing with the fact that you're pitching into an alcoholic environment, which makes it tough for yeast to get going.

I'm dealing with a stuck fermentation right now, too (also stopped at 1.020). I am currently building up a yeast starter with extra yeast nutrient. I plan to pitch at high krausen and hope they have enough gas in the tank to get down another tenth of a point. Though I can't speak to its effectiveness yet, maybe try that? Or you could just toss in some boiled yeast nutrient and try to goose the yeast that's left.

The problem is that yeast nutrient has a taste and that taste is not pleasant. Early on during the first peak of fermentation, it is possible for the yeast to absorb this, later on, especially close to finish, this won't happen so you will end up with a beer that tastes like yeast nutrient.

 

[dj zlim]

That is one of the big downsides of my setup right now - I'm using a cheap meat thermometer, so I don't have a great temperature check. The Anvil does have a common problem in temperature stratification, but I'm recirculating ~2/3 of the mash time so I figured it's well mixed. The times I checked the top of the mash, I was 5-10 F lower than target on the beta sacch rest (~140 F) and the mashout (~166 F).

I'm more inclined to believe it had to do with the mash, since the yeast formed a healthy krausen withing 12 hours of pitching (maxed out at 2 inches using a 6.5 gal carboy). I don't have a great aeration setup though, so that could be a factor. I'm racking into a carboy using an auto-siphon, which has a sprayer attached to the end. That's done well enough for other brews, but maybe the WLP029 needs more?