Re-freshing tired yeast

[pinnah]

So my question is about re-use of yeast that has worked on progressively increasing OGs.
eg. Pitched a starter of 1450 in 1.061 wort; fermented.  Pitched cake into wort OG 1.072. fermenting.

Now, I have heard that yeast get tired, and repitching from a 1.072 OG into something...say a 1.056 OG wort..is a bad idea because the yeast is pooped after a big job.

So can I refresh the vigor of the yeast by just making another starter and building it back up again?  Or is the tired yeast story bunk?

Thanks for your thoughts and experience.

[erockrph]

I'm glad you brought this up, as I've been thinking of this myself. I'm about to bottle my Quad that I brewed with the seasonal Wyeast Canadian/Belgian strain. I was thinking of trying to save the slurry, but I'm wondering if it's salvageable after over a month under a 1.090 brew.

[redbeerman]

It is always best to go from a lower gravity wort to higher, i.e. Oktoberfest to bock or doppelbock.  Yeast slurry can by nudged by adding a bit of cooled second runnings to the slurry.  That will wake them up.

[svejk]

My hunch is that your best bet would be to make a low gravity starter (1.030 or so) and pitch some of the yeast in it and use that for the next batch.  The reason I think it will be fine is because I have successfully used yeast from a bottle of Saison Dupont with only 2 steps (a cup of starter in the bottle itself, and that small starter into a half growler of wort).  I'm sure that yeast in the bottle was very tired at the point I woke it up and my two step process was a bad case of underpitching, but the beer itself turned out great.

In any case, by taking a chance and trying it, you'll be expanding your knowledge and can decide for yourself whether the tired yeast story has any merit.  I say go for it and post your results to this thread. 

[mtnrockhopper]

I don't think yeast in it's second generation is going to mind going from 1.07 to 1.05 wort too much. If the 1.07 beer underattenuated, that would be a sign that the yeast are stressed and gave up - then it might not be a good idea to use them further. If all signs are that they are healthy, give it a try.
 
Have you been using yeast nutrients? Also a good idea if you're reusing yeast (and not using them is probably the source of some tired yeast stories).

[euge]

One issue out of several I have with pitching onto yeast-cakes from successively stronger batches is that there is a lot of dead yeast in that slurry. And this is no good thing.

I prefer to pitch a cup instead of the entire slurry- but rebuilding a starter is even more preferable!

[a10t2]

If you have another option, I wouldn't harvest from a high-gravity beer, but if that's all that's available I say go for it. A 7-ish% beer isn't that much tougher on the yeast than a 5-ish%.

[tygo]

I'm playing with this right now.  I saved a slurry from a 1.096 dopplebock and let it settle out then dumped about half of it into a liter of 1.030 wort to give it a little feeding.  Once that fermented out I popped it in the fridge, which is where it's sitting right now.  Once the yeast settle out I'm going to decant off the spent wort and rinse it with cooled boiled water and then store under the same.