Re-Pitching Harvested Slurry Homebrewing

Hi all,

I've recently begun harvesting yeast from some of my more frequently used yeasts, and have finally gotten around to deciding to use one. However, I'm looking for a little advise/insight into the pitching rate of this slurry and was hoping you folks could offer some advice/experience.

I am brewing another 2.5 G, 1.059 OG, iteration of my ESB using 1968 (London ESB). I have one mason jar mostly full of harvested yeast. I would estimate that the jar has about 425 ml in it, 375 of which would be "compacted" yeast, and the rest the remainder of the previous beer. This yeast was harvested on Sept. 8, 2016 and has been kept in the refrigerator since.

Using most yeast calculators, I get a viability of around 60% given the harvest date. Using MrMalty, I get 10%. I can't believe that, so I have assumed a viability of 50% for the sake of conservativism.

Most of the information I have found shows that typical yeast concentrations of harvested slurry range from 1 to 5 billion cells per ml slurry. Assuming a slurry with 15% other trub material (yeast is strained prior to fermentation) and a concentration of 1.5 billion cells per ml slurry (again, for the sake of conservativism), MrMalty indicates that I only need 165 ml of this solution to pitch into a new 2.5 Gallon beer to pitch an adequate 100 billion cells.

Mathematically, this makes sense to me, but does this sound reasonable to you all?

The way I would pitch would be to let the solution warm up to room temperature prior to pitching, then pour the slurry into a measuring cup to the approximate required volume, then dump the rest to re-harvest after fermentation. Does this sound reasonable?

My alternatives are: 1) use this information to build a starter, then pitch as appropriate and pour the rest back into a re-sanitized jar

2) resuspend the yeast into the solution to make it a slurry, then add a small amount of sugar in order to "proof" the yeast.

Thanks for any input you guys can provide. Cheers!

Submitted October 31, 2016 at 11:17PM by HollywoodTK http://ift.tt/2dVKLYE Homebrewing