Amount of Yeast with Two Strains

[mls60442]

I apologize if this specific question has been asked before, but I could not find it within the forums after a quick search.

I am brewing a 3.5 gallon test batch of a big stout soon which has an estimated OG of 1.175 and an estimated ABV somewhere between 20% and 22.3%. The plan is to use two yeasts for the fermentation. We'll start with WLP007 Dry English Ale yeast for its flavor characteristics. After the 007 does what it can do, we plan to finish the fermentation with WLP099 Super High Gravity Ale yeast.

I entered both yeasts into the recipe design on BeerSmith and it is showing 383.5 billion yeast cells will be needed. It looks as if the program thinks we will be pitching both together which we will not be doing. If we start with an initial 2.0 liter starter of WLP007, it should give us roughly 438.4 billion cells. How do we figure how much WLP099 to pitch when it is time?

Also, one other thing. When the recipe was designed initially, we planned on only using WLP099. The estimated FG was 1.018. When we added the WLP007 to the recipe design along with the 099, the FG jumped to 1.029. Is this to be expected when using to yeast strains and if so, what would cause that?

This is the first big, big beer I'll be attempting to brew. It makes me feel like a first time brewer again at times. I appreciate any help you guys can provide!

 

[WoodlandBrew]

If some of your initial gravity is coming from extract that you have some more options.

I would start it as a 1.100 beer with WLP007 which would require a 250 billion cell pitch for a 0.75 billion per liter per degree Plato pitch rate. Give that about a week and then add the remaining 9 lbs of the extract. At this point the WLP007 isn't going to help much with fermentation because of the alcohol level. You're going to probably want 200-400 billion cells of the WLP099 to finish things out based on the amount of extract added. (Standard pitch rate would be to use 250 billion)

The final attenuation will be driven by the WLP099 which is pretty high, so you might be able to hit your 1.018 target, but as you may have heard, it can take some time.

 

[mls60442]

Okay, thanks for the info. We're going to be attempting to make this an all-grain batch. That's pretty much why it is a test batch at this point. We are taking a lot on and wanting to see our limits with the mash and fermentation for something this big. It's going to be a far reach for what we're aiming for.

You've given me a pretty good idea of what I need to do with the two strains. Thanks.