Need Help with Attenuation Problem

[Viridian]

Greetings again everyone - I hope you are all doing well. I haven't been on the forums much lately due to the start-up... its coming along. However, I come to you today asking for your input on some of our larger beers - and attenuation issues we are having with them. We recently brewed two big stouts, and have had attenuation issues with both of them - so I am sure there is something in the process that needs to be beefed up. All of the details are as follows:

10 GALLONS!

Recipe:
22lb 2-Row (1.8L)
6lb Flaked Oats
3lb Flaked Wheat
2lb Choc Malt (340L)
2lb Roasted Barley (300L)
1.5lb C-120
1.5lb Crisp Pale Choc Malt (400L)
1lb BlackPrinz (500L)

8oz cocao nibs @ KO
20oz Pasteurized Maple Syrup added to FVs

Mash Temp = 153, Mash pH = 5.3, FV pH = 4.9, OG=1108, Expected FG = 1022 (according to BeerSmith2).

Sparge Water pH = 5.5 using Phosphoric Acid

Water Profile: CA=134, MG=13, NA=75, SO4=33, CL=200

I added approximately 850 billion cells of London Ale III, added about 3.7 liters of pure O2 @ inoculation, and then added another 2 liters of pure O2 9 hours later.

Now, I realize that London Ale III is not necessarily happy with an 11.5% product, but I wanted to see how far I could go with it. After day 5, it halted at FG=1036 and about 4.25 pH, despite rousing the yeast and raising the temperature to 74 F. The taste was very fruity - so I think I stressed the London Ale III yeast - thankfully the stress makes a great complexity addition to the already robust stout.

Should my expected FG really be 1022? Why didn't I get full attenuation? What would you have done differently?

Thank you in advance everyone. Cheers.

[idylldon]

My $0.02.

The attenuation for that strain is listed at 71% - 75%, which means you should end up somewhere between 1.028 and 1.032 as an FG based on just the expected yeast attenuation with that OG. Since there are some dextrins in there from the caramel malt and you mashed at a temperature that can also add some dextrins, it seems you are in the ballpark with 1.036. In addition, and as you stated, that alcohol level is a bit above the maximum suggested for that strain. Considering all of this, I think the yeast strain did its best. I'm not sure why Beersmith would suggest 1.022 as an expected FG.

Wyeast also says that "this strain will finish slightly sweet," which, to me, suggests it has a bit of trouble with the longer-chained sugars. My guess is it powered through all the simple sugars and then got a bit too tired to do much more.

Cheers,
--
Don

[jebzter]

In a perfect mash, 20% of the sugars extracted from your mash will not be fermentable. This is a common issue in most recipe design programs, when they look at attenuation they look at the total starting, not the total fermentable. I agree with the previous comment, you probably fermented everything that was easy, what was left was what couldnt be fermented. If you want to get lower, you should mash lower, like 148F. This way you will not make much or any unfermentable sugars from the base malts. Rough numbers would indicate that you could get as low as 1.024 potentially with a highly fermentable wort. That factors in the 20% of it being dextrins and other non fermentable things. But then your looking at something like 78% attenuation, which is probably doable, but you will have to over pitch and step your ferm temps up at the right times.

[Viridian]

THanks for the input from both of you - I agree I think the strain just had enough. The reason BS2 indicated 1022 was because I put in the attenuation for the yeast at 80-85% or so (I can't remember exactly right now, I am not at the software). The reason I did this, is because I have been able to get London Ale III to consistently attenuate approx 90% for my NEIPA recipes (OG 1070 FG 1014 usually for flagship batches). So, I assumed 80-85 was achievable - but this was obviously an incorrect assumption.

Does everyone agree that my oxygen levels were good for the size of beer?

Also - Update:

On 4/1/18 we pitched about ~500 billion cells of White Labs WLP007, along with about 14oz pasteurized corn sugar between the 10 gallons. We did this in hopes that there was leftover fermentable sugars, and that we could consume them. Readings taken last night indicated that the OG is now down to 1032. My guess is that there should be at least another 5 points of fermentable sugar left, but we will see. I added corn sugar to jump start the yeast metabolism considering the high ABV solution that I pitched it in. In the future if I did this I would add oxygen.. I really should have.

Now - here is the really fun part - assuming that the fruity esters from LAIII really do this beer well - we will need to use this same method in the future and even commercially - considering the excessive fruitiness is from the stress induced on the LAIII.