Repitch yeast 1 month old

[DBear]

Howdy All,

I have ~1/2 qt. of wlp530 slurry that will be one month in the fridge next week. According the the Mr Malty yeast pitching calculator the yeast will be at 60% viability and will need 320billion cells for a 5.25 gal batch or 179ml. of thick slurry for OG 1.070.

First, based on the time in the fridge should I use it or chuck it. Second, although a thick slurry I would make a 2l starter just to make sure things going again.

Suggestions?
-Cheers

[Lars]

Depends... I've used older slurry. I'd make the call based on how confident you are in your sanitation, and how stable the storage temp was. When I pitched older yeast, it had been stored at a stable temp (not in a frost free fridge) and was clean going into a sanitized mason jar. If I had any question about the yeast other than age, I'd just grow up a new starter.