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.