Yeast Viability

Yeast & Fermentation
1

So I want to brew a czech pilsner next week. I have 250ml of slurry saved from brewing this beer Nov 2014 but brewersfriend says it’s 0% viable.

I went to my LHBS for Wy 2001, pilsner urquell yeast and the only pack he had was from Nov 2013. Obviously 0% viability. He gave it to me and said at least the yeast nutrient might still be good.

I made a one gallon starter and pitched both the smack pack, which didn’t swell much after smacking, and my slurry on Thursday evening.

Today there’s a good inch of foam krauesen on top and when I swirl it it rises up about 3 inches. So much for 0 viability. I’ll step it up once and then pitch it next week.

2

On the White Labs site, there is a statement, that even one year after expiration there will still be some live yeast in their vial.

With very old yeast I estimate 10% viability, when calculators say 0%, and go from there with my starter and step ups.

3

I had a smack pack of Wyeast 3787 that was over six months old that swelled right up last weekend…should have made a starter but my flask was busy :slight_smile:

4

I’ve had six month old yeast packs start right up and I’ve had three to four month old packs that were dead as a wedge. That said, I just pulled an Oktoberfest blend out of the fridge that’s dated October 1, '14. It’ll be interesting to see what it does.