Fri Mar 16, 2012 5:39 am
I generally estimate that 1 pack into 2L will double if fermented out. I don't have Yeast in front of me to reference the table in there. There is a diminishing return in terms of growth by pitching more yeast in less wort (4packs in 4L will grow less than 1 pack in 2L, though you'll still end up with more yeast).
I think you'll need to step up a couple times, or make a starter beer as suggested earlier.
When you say that you need to use them by the expiration, how close are they? That will also affect the viability of your yeast, and if they are older, you may need to step them up even more to get the numbers you want.
Spiderwrangler
PFC, Arachnid Deployment Division
In the cellar:
In the fermentor: Belgian Cider
In the works: Wooden Cider