beta-glucans

[Biergarden]

I'm rather skeptical of my hydrometer's claims of my final gravity. I made an oatmeal stout that should have completed fermentation several days ago. I ramped up the oatmeal to over 16% of the grain bill. I just used gelantinized oatmeal as well as a 90 minutes mash routine until the iodine test said I had conversion. The OG was 1.050 and on target post boil.
It's began to look like my FG is going to be 1.026, which leads me to believe that the load of beta glucans from the oatmeal has had an impact on the FG. I'm pretty sure the alcohol level is higher than what the hydrometer is leading me to believe.
What do you think?

 

[Gadjobrinus]

I don't think that's your beta glucan content at work - IMO 16% isn't enough to affect things like FG, lautering, etc. You might try a beta glucan rest next time with everything else kept constant but outside of that, sorry, I don't have an answer. What temp was your conversion step/rest? How thick was your mash?

 

[Biergarden]

Since the oatmeal was already gelantinized, I did a single step infusion mash at 152f for 90 minutes until I had conversion. I mashed for a light body since I knew this was going to be a chewy beer, but I'm a bit taken back by this high FG. I kept the fermentation temps in the mid 70's for five days, then let it taper down some.

 

[Gadjobrinus]

I probably shouldn't offer because I'm going on memory of a long time ago (I think it was probably Kunze), and I'd rather offer nothing than something unhelpful. But on thinking on this more, I don't know that b-glucans is as much an FG issue as an issue in lauterability, and mouthfeel. That, coupled with your relatively low % of the oats, makes me think doubly this probably has nothing to do with a b-glucans issue. I wouldn't be surprised if I'm not totally wrong and if so, apologies as I say above. And obviously your mash schedule isn't in the safely a-amylase-centric territory.

Stumped, but interested to hear from more knowledgeable folks. Sorry I couldn't offer much.

 

[Qhrumphf]

Agreed it's highly unlikely that beta glucans are your problem.

I'd doubt instruments (either hydrometer or mash thermometer) first, or perhaps water chemistry, or fermentation parameters.

What yeast, pitching rate, and oxygenation regimen did you use?

 

[Biergarden]

I used Mangrove Jack M15 Empire ale yeast stepped up to 2l. For water chemistry I use rain water pH 6.8 and add calcium sulfate to get the strike water to 5.8 which further dropped the mash pH to 5.3. I always recalibrate my thermometers with every session to make extra certain my mash temps are where they need to be. I did add rice hulls to the mash for sparge better. Run off was easy. I oxygenate with pure O2 at 2L for about 60 seconds. I'm wondering for I should have dosed again with O2 after 24 hours....
I fermented at 78*f which started within two hours of pitching and was really active for a few days. I brewed on 10/24/17
This is the first time I've used this much oatmeal in a beer so that has me wondering if these longer polymers are to blame, especially since the mouth feel is pretty thick itself.
I'm just not sure if it's me or the beer itself.

Anyways, thanks for all your input so far