Not to steal this thread, but I'm curious about how you guys are splitting these and building two starters off one pack. How do you know when each is ready to pitch? Are you just going through the builds a certain number of times, or looking for a specific amount in the mason jars after to know when it's ready?
It's fairly easy and straightforward.
Use a yeast calculator to estimate:
- # of cells on hand (due to age and handling),
- # of cells needed (pitch rate),
- and growth estimates based on certain variables
BrewUnited's Yeast Calculator
The calculator will open up subsequent steps where needed.
Just keep an eye on the steps and numbers and apply common sense. For example, it sometimes adds an extra step for growing only an additional 10-50 billion cells, just to make the intended count. This is nonsensical, as you can easily grow that amount in the previous step by using additional starter wort, or live with a slight underpitch.
There's also an option to calculate overbuilds, to save out extra slurry for your yeast bank or another brew.
Keep this in mind:
To
maximize growth per step,
minimize the inoculation rate (to 25 million cells per ml or even a little less) by using the maximum starter volume to accomplish that.
Typical process:
Make your (first) starter with the yeast pack on hand, say, a typical 1.6-2 liters in a 2 liter (or larger) flask on a stir plate (or orbital shaker).
When completed, cold crash for a few days until it all settled out, then decant, leaving only the yeast slurry behind.
If the flask is large enough add enough fresh starter wort and let her grow again in the 2nd step. Or transfer the yeast slurry to a larger flask (or split over 2 or more flasks) and make new starters with those.
If you're short on flasks or stir plates, you can always store slurries in (mason) jars, kept in the fridge, until you're ready to pitch or make new starters.
