Yeast viability with old WLP500

[Redhawk96]

I am brewing a 1.080 Belgian Trpel tomorrow. I had WLP500 collected from a previous 10 gal. batch of Tripel that has been stored in vials in my fridge since Jan. 2014.

My plan as to use all 4 vials and step up a starter, but I am starting to have concerns that there will not be enough viable cells. I pulled the vials out of the fridage to warm up 3 days ago, then pitched them into 1.5L of a 1.038 starter, and put it on a stir plate for 24 hours. From there, I cold crashed it in the fridge, and puled it out this morning to warm up, and will pitch it into a 3L 1.038 starter this afternoon, onto the stir plate, and ready to pitch into the wort tomorrow evening.

I do not have the capability to count cells, so is there any reliable indicator of my viabiity. Will a nice drop in gravity of my 3L starter be enough of an indicator that the yeast is ready to go?

I would still have the option of running to my LHBS this afternoon to purchase 2 vials of WL500 and make a fresh starter tonight. My main concern is getting a healty pitch into this 10 gallon batch. I would be interested in people's thoghts on this old yeast.

 

[flars]

You will need about 730 billion cells for 10 gallons of a 1.080 beer. I don't think you will get there with the old yeast. Purchase the new yeast for an approx 3.5 liter starter.
I like using this calculator. Used Pro Brewer 1.0 pitch rate and one month old yeast for the approximate 730 billion cell and starter size estimate.
http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

 

[Redhawk96]

That is where I'm leaning as well. I actually use the link you provided, and it is telling me my viability is near 0, so I think it would be risky to pitch the old yeast.

Thanks for the input.

 

[flars]

I have revived 0% viability yeast. It is time consuming though. Very low OG wort, 1.005 to 1.010, is recommended to limit the amount of stress on the old leathery cell walls.

 

[m00ps]

I would think that if the yeast fermented your starter completely doesnt that prove its viability? I mean it propagated fresh new yeast for you to use, right?

 

[Redhawk96]

I think the time consuming part is what is going to get me. If I would have started to step it up two weeks ago, I probably could have got there. I need to think ahead a few weeks and not a few days.

I can't change my brew date of tomorrow, so I think the best move is to go get a couple of new vials and pitch them into a starter and be ready to go.

I like that option better than way underpitching, or letting the wort sit un-pitched for a few days while a build the yeast.