Possible stalled/stuck fermentation with WLP530

[Queequeg]

Ok so I recently brewed a Belgian Stout and fermented with WLP530. The particulars;

SG 1.070
Target FG 1.010

Day 7 GU 1.021
Day 10 GU 1.018

Start temp 65F
Day 2 Ramp to 74 by Day 7

Mash temp 146F for 90 mins
Mash pH 5.3

Yeast starter was stir plate 1.5L to yield est. 0.5mil cells/ml/P

Oxygenated with Pure O2 for 75 secs at 1L/min flow rate.

blowoff activeity started after 12 hours, and was slow but steady. At temp on day 2 despite an increase of a degree there was a big blow off with lots of yeast in the blowoff container

Air lock activeity slowed and stopped around day 6, however pressure in the fermenter is still slightly positive. I am assuming continued airlock activity has ceased because the pressure isn't high enough to trigger the bubbling and is instead escaping through seals.

Obviously fermentation hasn't stopped, its just very slow. But I don't want it to stop.

Today I upped the temperature to 77F.

I have two speculative causes of this;

1) I mashed too low and didn't get conversion in the 90 min mash period. I did a starch test at the end of mashing and it was negative.

2) A lot of the yeast was lost in the blow off and now fermentation is taking much longer with the remaining yeast.


What course of action should I take?

I have the option to rouse with CO2, but I'm not sure that will help. Especially with Belgian strains.

I can pitch a new starter of WLP530 or try a different yeast to dry it out, say 3711 or champagne yeast?

I have some alpha amylase coming in the post if all else fails.

The beer tastes excellent, just a little too sweet. I would want to get the gravity at least below 1.015.

In B4 wait and see

 

[dmtaylor]

Patience. Have you allowed 3-4 weeks fermentation time? Because that is how much time this yeast needs. All you need to do it wait. Leave it alone.

 

[Queequeg]

Ok I will leave it be. I sample through a SS tap under positive C02 so the beer has been completely undisturbed. Is this typical of 530 to slow like this? I have read mixed reports.

I will leave it at 77F so help it out as from what I have read it needs to finish high in order to finish.

 

[beergolf]

I use 3787 a lot ( supposed to be the same as 530) and it is famous for taking off very fast and then slowing down and taking a long time to finish. Give it planty of time to finish. This yeast can fool you into thinking it is done and then slowly ticking off a few extra points.

Give it more time,