Yeast washing after 2 fermentations?

[JonM]

Hey everyone!
First, a little background: I have a 1.080 stout, fermented with 1056, that is stuck at 1.030. Brewsmith says it should finish at 1.020 (it has a LOT of flaked barley). Fortunately, I also have a moderate gravity stout, also fermented with 1056, that is ready for bottling this weekend. My plan is to bottle the mod. gravity stout, rack the stuck stout onto the cake and hopefully get it unstuck and finished out.
My question is, after the stuck stout is done, is it worthwhile to wash the yeast that had fermented the mod. gravity stout and then finished the high gravity stout? My gut says yes, but I'm hoping to get some more experienced opinions on this.
Thanks!

 

[KCBrewer]

I've read a lot of differing views on how many generations you should go, but 5 seems to be commonly accepted as okay. The main concern is that yeast start to morph and take on different characteristics if not properly cared for, and create off flavors. I don't see problem with what you are planning to do though, and wouldn't hesitate to do it myself. I'm sure someone more experienced with this will chime in if I'm wrong though.

You may also just have an issue of too many non-fermentables. What was your mash temp and what is the recipe?

 

[JonM]

Thanks! It was a 2.5 gal batch that is reportedly Zymurgy's clone of Bell's Kalamazoo Stout. (My O.G. is pretty high for Kalamazoo, though) It is:
2.50 lbs. 2-row
1.75 lbs. flaked barley
1.25 lbs. roasted barley
.50 lbs. Munich
.50 lbs. Special B
.20 lbs. Black malt
1.30 lbs. light DME
Mashed at 154, single infusion, batch sparge.
The 1056 in the moderate gravity stout (also a 2.5 gal batch) is a first generation. My only concern is that putting a beer that is already 6.7% on that cake would make future generations go a little screwy, but my gut says it'll be fine and that I should just wash it and count it as having 2 generations after this is all done.

 

[Hermit]

Wash some of the cake, feed it until it is active and pour it into the 'stuck' fermentation. I think Chris White suggests using an active starter when dealing with a stuck fermentation. Yeast are pretty efficient. I think you may have no fermentables left.

 

[DrawTap88]

+1 to what hermit said. If you use non-active yeast, they'll recognize the alcoholic environment and flock out without doing anything.

 

[JonM]

How about this: When I put the 1.080 stout in the fermenter, I poured the trub into a growler and let it settle out. Then I took the clarafied wort (maybe 2-3 pints) from the top and froze it.
I can thaw that, dilute it to 1.040, boil it, cool it, then pour that onto the mod. gravity stout's cake. After about 48 hours when it's good and active, rack the stuck stout into that? Basically make a starter without the risk of contamination by washing, transferring vessels, etc.

 

[TristanL]

Like others have stated I'd just take a small amount of the slurry from your medium gravity stout (100ML or so) and make a 500ML starter, cool it and pitch the yeast. There isn't any need to "wash" or "rinse" the slurry after 2 pitches. When the yeast is at the height of activity pitch it into your high gravity stout. It can't hurt, and it may attenuate a little more.

With the grist you listed it is possible that all the fermentables have been consumed. Also, have you calibrated your thermometer lately? A few degrees in the mash can make a difference, although slight.

Here is an interesting option to consider; why not mix the two stouts and see what kind of flavor combination you achieve? It would be hero or zero. It might make the high gravity more drinkable or it might ruin both beers