Wyeast Manufacture Date and Mr. Malty Pitch Rate Calculator

I have a smack pack manufactured on June 29, 2009. Wyeast guarantees the viability of their yeast for 6 months after the manufacture date. However, when I enter the date into Mr. Malty it says that the viability is 26% and that a minimum of 2 packs are needed to achieve a cell count of 194 billion (for a 1.053 OG beer).

Are the viability/starter size accurate? Is it necessary to use multiple packs or to step up the starter using one pack, or can I just make a starter as I normally would (calculated with the default viability setting on Mr. Malty)?

I've never entered the manufacture date of the yeast into the calculator and have not had problems with my starters in the past, but wanted to see if anybody has any thoughts/advice.

Your yeast is fine. Mr. Malty is insane for telling you to buy two packages. I'd just make a step starter to be safe.

Sounds like the actual question is:

What % viability does Wyeast guarantee for their yeasts at 2 months, 3 months, 6 months, etc.

This is Wyeast's warranty:

Our Product Warranty states that we guarantee the viability of the yeast in our Activator™ packages for 6 months from the manufacture date assuming that they have been properly shipped, stored and handled.... During this 6 month guaranteed shelf life, some loss of viability is to be expected. This will vary from one strain to another.

Either way you are going to make beer. Yay! But if you follow Mr. Malty you will probably make better beer....

michael.berta said:

Either way you are going to make beer. Yay!

Click to expand...

Very true

I plan to make the step up starter as Suthrncomfrt1884 suggested. The first step will be to make a starter using Mr. Malty's calculations with the 6/29/09 date to get to the equivalent of one new smack pack i.e. ~100 billion cells. The second step will be to make a starter using Mr. Malty's calculations with today's date to get to the target cell count and assuming that my first step starter = 1 smack pack.