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Neddy · **Posted:** Thu Jun 16, 2011 2:27 pm

I was fooling around with Jamil's yeast calculator tonight. I was thinking about brewing a Bo Pils next week using a pack of yeast I bought a few weeks ago. Production date on the yeast is 4/13/11 when plugged into Jamil's calculator shows a 55% viability which means I'd need a GIANT starter.

I know jamil's done his homework but does yeast viability really drop nearly 50% after 2 months from production when stored cold in the fridge?

dunleav1 · **Posted:** Thu Jun 16, 2011 2:30 pm

Neddy wrote:

I was fooling around with Jamil's yeast calculator tonight. I was thinking about brewing a Bo Pils next week using a pack of yeast I bought a few weeks ago. Production date on the yeast is 4/13/11 when plugged into Jamil's calculator shows a 55% viability which means I'd need a GIANT starter.

I know jamil's done his homework but does yeast viability really drop nearly 50% after 2 months from production when stored cold in the fridge?

Yes.

Lichtersnatch · **Posted:** Thu Jun 16, 2011 2:37 pm

I believe Jamil used Methylene blue testing for the calc (from what I've heard 2nd hand), which can be a little bit inaccurate under 80% or 90% viability. But having said that... yes, liquid yeast goes downhill fast.

siwelwerd · **Posted:** Thu Jun 16, 2011 5:25 pm

Neddy wrote:

Production date on the yeast is 4/13/11 when plugged into Jamil's calculator shows a 55% viability which means I'd need a GIANT starter.

Or you could step it up a couple times.

ntillemans · **Joined:** Sun Mar 30, 2008 8:55 pm **Posts:** 60

siwelwerd wrote:

Neddy wrote:

Production date on the yeast is 4/13/11 when plugged into Jamil's calculator shows a 55% viability which means I'd need a GIANT starter.

Or you could step it up a couple times.

Stepping up is a great idea when you need to grow a lot of yeast.

Doesn't hurt to have a 5L Erlenmeyer flask either.

Sometimes it takes both...sometimes...

Mr Malty yeast viability calculations

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