Stuck fermentation, should I intervene?

[IndyBlueprints]

Brewed an all grain Munich Dunkel. Here's the stats:

6.5 gallon batch.
Munich malt 10 & 20, 11.75# total.
2 oz chocolate
2 oz chocolate rye.
Mash ph 5.13@ 168F.
O.G. 1.060.
#wlp833 German Bock Lager yeast.

Brewed on my Electric RIMS with PID controller, gas fired BK, so mash temps and times were right on.

Using Brulosophy's 'quick lagering' method, I fermented at 48-50F for 7 days, until it reached roughly 50% attenuation, at 1.030. Then moved it to 68F to finish. It's now been stuck at 1.030 for 8 days.

Should I put my stir plate under it to mix it it up?
Should I agitate it by rocking the glass carboy?
Or should I just accept that it's going to be a low ABV sweeter beer?

And WHY would this happen?

Believe it or nor not, this is the first time I've had a stuck fermentation in 20+ years of fermenting.

 

[Steveg229]

Did you mash at 168F or 158f?

 

[passedpawn]

8 days at 1.030 @ 68F does seem like a problem.

Since you had some normal fermentation already, and the ABV is not that high, the yeast should still be quite active. Seems like you had a mash problem and now you've got unfermentable sugars (especially if that mash temperature was correct!)

I'd recommend adding additional amylase enzymes to the fermentor, then waiting another 2 weeks for it to finish. It will likely finish lower than you wanted (probably 1.008 ish). For me, that would be far better than a 1.030 beer, but you'll have to decide.

 

[Alain2]

Did you have a big 2 liter starter for that 1.060 lager?

 

[IndyBlueprints]

I mashed at 150F for 60 minutes, then raised to 168F to rinse with strike water.

I did have a roughly 1.5 liter starter.

 

[millsbrew]

Per my LHBS, 833 is pretty lazy. But 1.030 is high. Perhaps create another starter and add some of the beer to the starter before pitching. I make a 2L starter and dose with pure O2 when I do lagers.

 

[jan_b19]

Give the fermentation vessel a light swirl (not too rough dont want to much O2) and raise the temperature slightly, if there's no reaction you can add more yeast or just bottle it like it is.

 

[IndyBlueprints]

Going through my "not-so-detailed-notes", and my somewhat fuzzy memory, I think I may have rushed my yeast starter, and not given it enough time. If that is indeed the case, then am I correct in assuming I 'underpitched' the yeast? If that's the case, could that be the cause of the 'stuck fermentation', or possibly 'done fermentation' of the inadequate yeast pitch?

 

[passedpawn]

Going through my "not-so-detailed-notes", and my somewhat fuzzy memory, I think I may have rushed my yeast starter, and not given it enough time. If that is indeed the case, then am I correct in assuming I 'underpitched' the yeast? If that's the case, could that be the cause of the 'stuck fermentation', or possibly 'done fermentation' of the inadequate yeast pitch?

Nope. The cause is most likely back in the mash.

 

[IndyBlueprints]

Nope. The cause is most likely back in the mash.

OK. Now a couple of questions on that subject. I just recently built a RIMS system, and am still getting the hang of it. I understand that if you mash too high, you will not convert the starches to sugars as well.

Are there any issues starting the mash at too low of a temp, and slowly working up to temp? I am assuming there isn't, giving the somewhat popularity of doing step mashes. I have been heating my mash water up to about 145ºF before I add it to my mash tun (from the bottom), which already has my grains in it. I then set my PID to my desired temp, and it might take 20 minutes to get up to that temp. No issues with that method, is there?

Then, after my required mash time, I crank my PID up to about 168º for fly sparging. It takes 15-20 minutes to get there, then I start my pumps and start sparging. Any issues with that method?

 

[passedpawn]

OK. Now a couple of questions on that subject. I just recently built a RIMS system, and am still getting the hang of it. I understand that if you mash too high, you will not convert the starches to sugars as well.

Are there any issues starting the mash at too low of a temp, and slowly working up to temp? I am assuming there isn't, giving the somewhat popularity of doing step mashes. I have been heating my mash water up to about 145ºF before I add it to my mash tun (from the bottom), which already has my grains in it. I then set my PID to my desired temp, and it might take 20 minutes to get up to that temp. No issues with that method, is there?

Then, after my required mash time, I crank my PID up to about 168º for fly sparging. It takes 15-20 minutes to get there, then I start my pumps and start sparging. Any issues with that method?

No problem with that. Enzymes will work even at room temperature. But their activity is much less as the mash gets colder, especially for alpha amylase. Both alpha and beta amylase are highly active in the 150-160 range, which is why we mash there.

If you mash too high, you'll permanently denature the enzymes and get no sugar conversion.