Yeast performance - old vs new

[Flipadelphia]

Just something my friend and I were talking about and wanted some other opinions on the topic.

Let's say you take two liquid yeasts, any style. One dated February 1 2014 and one dated July 25 2014 (today).

You want to step each up to say, 250b cells. You use yeastcalc/mrmalty whatever, and do the math and correct start to step each up to the assumed correct yeast cell count (the older one requiring much more DME of course).

Would these yeast starters perform identically?

Basically I'm asking if older liquid yeast stepped up appropriately performs the same as brand new fresh yeast, each stepped up to the same assumed cell count.

Thanks.

 

[flars]

I would start the older yeast in a 1.010 wort to avoid stressing the yeast. Then step it up from there with 1.038 worts. I would expect each to perform the same if neither one was not severely mishandled at some point.

 

[danath34]

I think you have a greater chance for mutation with the older yeast.

however, you are also selecting for whatever traits allowed the cells in the older yeast to outlive the others for that period of time. dunno if that would be a good or bad thing to select for in terms of effect on the final product...

 

[day_trippr]

Mr Malty says the Feb 1 2014 vial would be 10% viable. That's a fairly significant die-off, and goes to the point made just above about whether the mortality caused a character shift (I have no idea - and don't recall the topic being addressed in Yeast).

If one wants to preserve the intended character of a particular strain it's safe to say a much fresher batch will have fewer questions to raise...

Cheers!