[Steve L]

Just figuring up my yeast pitching rates for a 2.5 gallon 1.066 IPA I'm brewing next week. I need 115b cells and a 1 liter starter with my vial of WLP001 (viability is around 67b cells) should yield around 185b cells. I'm torn between just doing a half liter starter the night before or doing a 1 liter starter a few days ahead and pitching about 3/4 of it. Does this seem like a 50-50 proposition or is the 1 liter route likely to be a bit more accurate?

[duboman]

Why don't you make the larger starter and before crashing to decant, swirl it up and save about 250ml to use for another batch?

[Steve L]

Why don't you make the larger starter and before crashing to decant, swirl it up and save about 250ml to use for another batch?

I think that is the way I'm leaning. I am planning a 1 gallon test batch of an IPA soon, and that 250ml should be about right for that. Thanks for the help

[S. cerevisiae]

I would pitch the contents of a vial without a starter and crop for your next beer.  A White Labs vial is enough yeast for 2.5 gallons of wort.  Remember, the difference between 65 billion yeast cells and 130 billion yeast cells is approximately 90 minutes of propagation time, as the cell count doubles roughly every 90 minutes until the medium is exhausted of maximum cell density is reach, which is 1.9 trillion cells for 2.5 gallons (~9.5L).

number_of_replication_periods_necessary_to_hit_max_density = log(1,900,000,000,000 / 65,000,000,000) / log(2) = 5

Hence, the yeast biomass needs to five 90 minute replication periods past the log phase to fully saturate the wort with yeast cells.

[duboman]

Why don't you make the larger starter and before crashing to decant, swirl it up and save about 250ml to use for another batch?

I think that is the way I'm leaning. I am planning a 1 gallon test batch of an IPA soon, and that 250ml should be about right for that. Thanks for the help

I do this anytime I am using a liquid strain I plan on using again, I simply make a larger starter to account for a 500ml slurry to save. When I am ready to brew again I simply start up the saved yeast and repeat the process, it really works out well and saves a lot of money on yeast!

[Steve L]

I would pitch the contents of a vial without a starter and crop for your next beer.  A White Labs vial is enough yeast for 2.5 gallons of wort.  Remember, the difference between 65 billion yeast cells and 130 billion yeast cells is approximately 90 minutes of propagation time, as the cell count doubles roughly every 90 minutes until the medium is exhausted of maximum cell density is reach, which is 1.9 trillion cells for 2.5 gallons (~9.5L).

number_of_replication_periods_necessary_to_hit_max_density = log(1,900,000,000,000 / 65,000,000,000) / log(2) = 5

Hence, the yeast biomass needs to five 90 minute replication periods past the log phase to fully saturate the wort with yeast cells.

If I do a direct pitch of the vial, would there be any negative flavor issues in under pitching by 30 billion cells, or is this a negligible difference? Then again, over pitching a hoppy beer isn't good either I imagine.