Yeast Viability

[mlmeeks]

I recently purchased the Wyeast 2206 Bavarian Lager Yeast. As of today it is 126 days old. Production date of 8/30/16. Would it still work with an adequate starter or should i trash it?

 

[flars]

It will work with a starter. Take a look at this pitch rate/starter calculator.
http://www.brewunited.com/yeast_calculator.php
Overbuild the starter and have some yeast to harvest that has not undergone the stress of fermenting a beer for your next starter.

 

[rhys333]

Using the highly accurate (ahem) rule of thumb, 15% loss per month, you're probably at about 40% viability right now. Just make a starter with that in mind and you're all good.

 

[kh54s10]

I use this calculator: http://www.yeastcalculator.com/

I thing all the online calculators use the production date to calculate starting viability.

 

[rhys333]

I stopped using the calculators a while ago, as I noticed they overestimate cell loss by a huge amount. That said, first generation yeast tends to need a larger starter than harvested slurry (perhaps due to poor handling during shipment).

 

[flars]

Using the highly accurate (ahem) rule of thumb, 15% loss per month, you're probably at about 40% viability right now. Just make a starter with that in mind and you're all good.

The rule of thumb may not work all the time. I think the viability calculators used by Brewers Friend and Brew United are good for not so old yeast but are lacking for very old yeast.

I was refreshing harvested yeast. I had two pint jars of WY 3711 and one quart jar with harvested yeast. Tossed the greyish looking yeast in the pints from April and June and kept the yeast in the quart jar also from June. The beer above the yeast in the quart jar that I saved was very dark indicating extreme oxidation but the yeast was creamy white.

Looked more closely at the jars label when getting ready to pour 50 ml of the yeast into the starter wort. Date was June 2015. Took almost 24 hours for the fermentation to begin but I have a lot of new yeast in the flask.

Poured the remaining yeast and beer into two pint jars. The beer has cleared to a nice clear yellow, same color as the petite saison fermentation it came from.

Now I just have to consider whether this old revived yeast will still have the same fermentation properties of fresh WY 3711.