Yeast Viability

[SEndorf]

My LHBS dude told me today that White Lab yeast is designed to contain at least 100 billion cells up to the "use by" date.
Therefore, viability calculators are inaccurate and not necessary.
Anyone else heard this? If this is old news, I won't have to contact them for confirmation.

 

[CA_Mouse]

The packages contain at least 100B cells at time of packaging according to White Labs. Viability will depend on how old the package is (they still state they put a 4 month date on it, but Chris White has said that they remain viable for up to 6 months), how well it was stored (35*F is recommended), if it was allowed to sit at room temperature for any length of time, etc.

I believe that Chris White even addressed this on either the Brewing Network's Session or on BeerSmith's podcast recently.

 

[Build]

I've read that White labs cell count varies some by strain (70-120b), but 100 billion is about the average. I use that as a guide and work up from there.

 

[pdxal]

Yeast viability, and therefore # cells, decreases over time. They're a perishable food product, when you get down to it. Living cells die of without food.
Packaged at 100B will be going down from there, so 3 months on the shelf, after shipping, can't possibly result in the same 100B at 3 months. That's where the online pitch rate calculators like Mr. Malty come in. Argue rate of death, perhaps, but there has to be a decline.
Not sure I'd trust the LHBS dude after hearing him say this.