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zanemoseley · 10-13-2010, 03:20 AM

The way I've been re-using yeast is to harvest the small amount of slurry at the bottom of corny's after a keg is floated. Then I make a starter with 400-600ml of DME wort and put it in a sterile canning jar in the fridge until I decide to reuse. I just recently used a 6 month old jar of WL Irish Ale yeast to make 10 gallons of Oatmeal Stout, after stepping up of course.

So does the yeast degenerate batch to batch or does the infusion of 10 gallons of tasty wort revitalize the yeast colony and weed out any unhealthy yeast. I know there are probably some factors like sanitation that will effect the end result. But as a whole am I safe reusing yeast 3,4,5 or 6 times in a row by harvesting from the bottom of a corny?? I'm not fond of washing yeast from the bottom of a fermenter as I put all hop and break material in the fermenter. So the most pure yeast I can get my hands on is in the bottom of the keg after the majority of hops/break have left the scene.

I've had good results so far with this practice but I'm curious what some more experienced people have to say because I don't want to learn a 10 gallon lesson if at all possible.

samc · 10-13-2010, 03:24 AM

They mutate. At some point you will most likely have something very different then you started with. That might be good or bad. It's not recommended to go more than a few generations all though several people are liable to pop up and tell me I am wacko.

JonK331 · 10-13-2010, 03:42 AM

I talked to a pro brewer a year or two back who said that he used his yeast (safale -05 in this case) nine times before getting rid of it and starting fresh. This was in super consistent brewery conditions though.

zanemoseley · 10-13-2010, 11:55 AM

So is there any way to tell at which point to dump it or do you just have to have a feel for it? I know I'm not good a smelling a starter and telling much from it. I though my starter with the Irish Ale yeast smelled kind of like apple juice or something.

COLObrewer · 10-13-2010, 01:02 PM

The answer is, yes. Some yeast die, new yeast are created, yeast split to make other yeast, so the new yeast is a "clone" of sorts of the sister yeast. This is what they are doing when you make a starter.

Yeast mutate because of what we do to it, for instance since you are harvesting from your kegs, you are selecting only the least flocculant yeast in the batch, so eventually you may have trouble clearing the beer, but maybe not. Yeast are awesome warriors and have a will that we cannot crush, they are my hero friends.

I've never harvested from the keg, I probably will now since my juniper yeast appears to be extremely flocculant, . . . . and, the fact that I harvest alot.