Top Cropping Pitching Rates

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michael.berta

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Hi Everyone,

When harvesting yeast from the top of a fermenter during active fermentation how much would you need for the next batch? Say for example going to a 1.050 ale wort. The Mr Malty pitching rate calculator seems to work for re pitching from a slurry but doesn't take into account top cropping.

Thanks

Mike
 
A quick google search tells me that at high krausen, yeast cell density is about 100m / ml. Not sure if that's a reliable number of not.

Yeast from a krausen would be a type of slurry. I would take the MrMalty numbers, which are in billion/ml, set the slider to 1, and multiply "#ml of yeast needed" by a factor of 10 if you're not planning on doing a starter. Roughly 2 liters of krausen seems like a bit much to me. That might not leave enough left in your fermenter to finish the original job.

I would probably take 1 liter of krausen and make a starter from that.
 
I wonder if by the time you're starter is mature (from using krausen yeast and not slurry yeast) you'll have a good thick slurry at the bottom of the primary anyway.

It might be a tie (but waiting for the yeast to settle requires less effort).
 
Nateo said:
A quick google search tells me that at high krausen, yeast cell density is about 100m / ml. Not sure if that's a reliable number of not.

Yeast from a krausen would be a type of slurry. I would take the MrMalty numbers, which are in billion/ml, set the slider to 1, and multiply "#ml of yeast needed" by a factor of 10 if you're not planning on doing a starter. Roughly 2 liters of krausen seems like a bit much to me. That might not leave enough left in your fermenter to finish the original job.

I would probably take 1 liter of krausen and make a starter from that.
Click to expand...

Any other thoughts on this? I have top-cropped for a while and I have never gotten incomplete fermentations from top-cropping too much, but I usually air on the side of taking a lot, and I've always wondered if I'm compromising the currently-fermenting beer in any subtle way.

I can say, though, that I'm pretty sure I've taken as much as 2 liters from a 5 gal batch, and, while it's not as if I've never had a stuck fermentation, I haven't noticed any correlation between getting stuck and top-cropping.
 

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