[HydraulicSammich]

I decided to build Tom Schmidlin's top cropping gadget and successfully harvested some nice white slurry approximately 48 hours into fermentation of a 1.065 IPA.  Of course everything was sterilized or sanitized.  I cold crashed the slurry and came up with approx 125 mls of slurry with about the same amount of beer on top.  No trub layer.  Could someone help me estimate the viability of this slurry so I could step it up if need be for a new beer.  I am looking for a useful estimation.  50%, 25%, what has been your recurring best guess.  I realize I could count cells but am not set up nor do I really want to get that involved.  I have read quite a bit on the subject but can't seem to narrow down a good way of estimating.  Thanks.

[morticaixavier]

i would think it would be pretty much 100% or as close to that as it ever is as of harvest. General rule of thumb is I think 20-25% loss per month of storage although I've heard some folks speculate that if it's properly stored this is probably overly conservative.

[HydraulicSammich]

Morticaixavier, that is interesting.  I was reading on Wyeast packaging, it mentions it contains 125 mls of yeast an nutrient.  So, Brewer's Friend Pitch Rate Calculator predicts that if the viability is 1 billion per ml then a 1 liter starter would be perfect.  But, if I intentionally underestimated it by 50% calling the viability .5 and using a starter of 2.7 to collect adequate cells.  Do you think I would be over pitching in 5.5 gallons if I were wrong?  Just trying to be on the safe side of viability.

[klickitat jim]

When fresh, top crop is probably 95%+ viable. Trube % is the question. Given that some folks dump their wort on an old yeast cake I doubt you would get hurt by over pitch.
I think I would use 100ml of top crop in a 2000ml stir starter and not worry about it

[morticaixavier]

Yeah I think Jim is probably right on. make the normal starter you would make for a fresh wyeast or whitelab pitch

[HydraulicSammich]

Just wanted to followup on this discussion.  One week after harvesting I planned to pitch the whole 125 ml into a new 5.5 gal batch.  I got a little nervous about the viability and pitched it into a 2 L starter.  Then decanted and pitched as planned in 7 days.  Fermentation took of nicely and collected another 140 ml from the second beer.  What a sweet easy way of yeast collection, saving a little money, and having a little more fun. 

[klickitat jim]

Good deal! There's more than one way to skin a cat. Glad that's working out for ya