Stuck Fermentation: Am I about to make a terrible mistake?

[Iowa Brewer]

Hey all!
Last Sunday I brewed a SMaSH German pilsner (German Pils & Saaz) with two packets of Saflager 34/70.
OG was 1.046 and it took off like a rocket, but now stuck for four days at 1.014 (Est. FG is 1.006).

There are a couple things that may have caused this:

• Forgot to add yeast nutrient
• Lowered temp from 65F to 57F (slowly) after I realized my fermenter was only keeping 8.5psi pressure and was worried that wasn't enough pressure to suppress unwanted flavors

I've slowly raise temp back to 64F, but to no effect.

My plan is to relieve pressure, open a port, and sprinkle one more packet of 34/70, reapply pressure to 8.5psi and raise temp back to 64F to see if that might finish the job.

Is this a cliff I need to be walked back from?

As always, many thanks!

 

[RM-MN]

Things to consider that you haven't mentioned.
The temperature during the mash affects the final gravity.
Heating during the mash can denature enzymes raising the final gravity.
Using a refractometer or an electronic hydrometer can give false results.
The estimated final gravity is just that, an estimate. YMMV

Raising the temperature higher than 64 degrees may help if the ferment is really stuck as can swirling the fermenter to rouse the yeast. Adding more yeast at this point in the ferment rarely helps.

 

[AlexKay]

Taste it!

Always drink the hydrometer sample.

If it’s undrinkably sweet, consider adding glucoamylase.

If it’s drinkable, you’re unlikely to make it better at this point. Work with the advice from @RM-MN for the next batch.

Edit to add: I’ve never heard of 34/70 getting stuck. A few years back I posted something similar to this about my high-FG Doppelbock, but … it wasn’t stuck then either.

 

[Iowa Brewer]

Things to consider that you haven't mentioned.
The temperature during the mash affects the final gravity.
Heating during the mash can denature enzymes raising the final gravity.
Using a refractometer or an electronic hydrometer can give false results.
The estimated final gravity is just that, an estimate. YMMV

Raising the temperature higher than 64 degrees may help if the ferment is really stuck as can swirling the fermenter to rouse the yeast. Adding more yeast at this point in the ferment rarely helps.

Thanks, RM-MN. The mash temp and refractometer shouldn’t be an issue. I’ve measured the gravity in a few different ways.

Although it rarely helps, couldn’t have a negative effect?

 

[Iowa Brewer]

Taste it!

Always drink the hydrometer sample.

If it’s undrinkably sweet, consider adding glucoamylase.

If it’s drinkable, you’re unlikely to make it better at this point. Work with the advice from @RM-MN for the next batch.

Edit to add: I’ve never heard of 34/70 getting stuck. A few years back I posted something similar to this about my high-FG Doppelbock, but … it wasn’t stuck then either.

Cool. Thanks, AlexKay!

 

[AlexKay]

Cool. Thanks, AlexKay!

On second thought, if it’s undrinkable, add glucoamylase and another yeast packet. Nothing to lose at that point, after all.

(I think you’ll find that it tastes just fine, though! Yeast rarely leave food on their plate, so it’s much more likely you gave them a bunch of dextrins they weren’t able to eat.)

 

[Iowa Brewer]

On second thought, if it’s undrinkable, add glucoamylase and another yeast packet. Nothing to lose at that point, after all.

(I think you’ll find that it tastes just fine, though! Yeast rarely leave food on their plate, so it’s much more likely you gave them a bunch of dextrins they weren’t able to east.)

Gah! Yeah, it wasn’t an ideal brew day.
Even by making adjustments, I couldn’t seem to get the mash pH down to where I wanted it.

 

[doug293cz]

If it’s undrinkably sweet, consider adding glucoamylase.

On second thought, if it’s undrinkable, add glucoamylase and another yeast packet.

I recommend against adding glucoamylase (amyloglucosidase) unless you want to end up with a brut lager. Glucoamylase will convert all dextrin and any remaining starch to fermentable sugar. This can lead to an FG below 1.000. It's better to try adding alpha amylase to the fermenter. Alpha amylase will convert any large dextrins into limit dextrins and fermentable sugar. It will also convert any remaining starch into limit dextrins and fermentable sugar. The limit dextrins will keep your FG well above 1.000.

Brew on

 

[AlexKay]

Gah! Yeah, it wasn’t an ideal brew day.
Even by making adjustments, I couldn’t seem to get the mash pH down to where I wanted it.

That’s too hard to do. Make your best guess, measure mash pH (with a meter, not strips) and make adjustments when it’s time for the next batch.

That’s if you’re going to measure it at all. I’d do every one of the following things first:

1. Ask local home brewers what they find they need to do for water. Ignore the ones who start rhapsodizing about sulfate and chloride, and focus on whether the water makes decent beer without a lot of additional effort.
2. Get a water report, post it on the Brew Science forum here, and ask “is there anything I need to worry about here?”
3. Buy or make RO water and use that.

 

[dmtaylor]

Your estimated FG is all wrong, not sure where you got that from. W-34/70 averages around 75% apparent attenuation, which for a 1.046 OG beer should be about 1.012. So 1.014 isn't too far from that.

Might have been a mash temperature thing.

More yeast won't help at all, no way no how.

Adding enzymes is a bad idea IMO. I'd just drink it as is.

If you want higher attenuation (lower FG) then next time use a more attenuative yeast. W-34/70 is one of the least attenuative among lager yeasts. I like S-189 which for me has averaged 81%. Or Diamond, that one is about 81% as well. Even these would get your FG to about 1.007-1.008 at best, not 1.006 which was a lofty goal methinks.