Hi,
I am on the fence of whether to build up a starter or not for my 12 gallon lager.
I read somewhere 1.5 billion per liter for a 1.050 lager for a pitch rate?
So at 1.5 billion per liter lager pitch rate at 12 gallons = 45.4 liters X 1.5 = 68.1 billion cells.
from Whitelabs site -
Although the PurePitch® packages state a cell net volume of 40 mL, actual volumes range from 40 to 50 mL. In our production, we allow for cell counts of 1.5 to 3.0 billion per milliliter which will produce 60 to 120 billion total cells if 40 mL. We target the high range of cell counts and fill volumes in our production and packaging processes, however as stated above, the reality of cell biology is that those numbers will vary.
You need about 850 billion cells for a proper pitch. That’s 45.4 liters x 1.5 billion cells per liter multiplied by 12.5 degrees Plato(1.050). With the yeast being 4 months out from its production date You can figure about 40% viability which would mean around 40 billion cells in the packet, assuming the packet started at 100 billion cells This estimate errs on the safe side.
This calculator will help you figure out what you need in the line of a starter.
This is definitely a situation where I’d make a 2 L starter from a single pack, brew a 6 gal batch, then harvest and re-pitch for the 12 gal.
Or if you aren’t kegging or don’t care about a half-empty keg, pitch two packs directly into a 3 gal batch, then put the 12 gal of wort onto the yeast cake.
I appreciate all the feedback guys.
Yes a 2 gallon starer with 2 packs is close to what the calculator says.
I usually step up a fresh pack in 2, 1 gallon starters and try to pitch the second one at full krausen which also aligns to the calculator.
I thought the pure pitch packs might have had more cells to start with and would have been closer than to the total I needed and I had no idea the yeast falls so far so fast after the production date.
I have been told by a white labs rep that viability in a pure pitch pack after six months stored in a fridge is 75%. That might be optimistic, but your viability might still be better than 40%.
Also, white labs publishes qc data including cell counts for each pack of yeast. You will need the lot numbers from your packs of yeast. They may have started off with way more or less than that 100 billion cells.
My bet is that viability is probably around 20%, but maybe it’s a little higher if White Labs says so. I’d go with a 2-gallon starter with all 3 packs if you’ve already bought them, although you truly only need 2 packs or maybe could even get away with just 1, but 2 would be better.