I usually have my slurry chilled in a mason jar for a few days before reuse such that there is a cup or less of compact yeast and the rest is wort / pre-boiled water.
I decant all the liquid on top and add fresh wort to mix up the thick yeast cake.
When using the online calc should the slider bar for yeast thickness be set all the way to 4.5 in my case? I know it’s pretty subjective since I don’t have a way for counting yeast but what do you guys do?
Have you ‘washed’ your yeast previously with sterile water, or is it straight sludge from the primary?
If I remember correctly, the center of the slider on Mr Malty’s pitching calculator assumes a “normal” distribution of yeast and other gunk. If you wash out all that junk, I’d move it closer to the “pure yeast” end of the slider.
In my experience it stops compacting after about 3-4 days at refrigerator temps. So if you’ve had it chilled for about that long I would go with 4-4.5 billion/mL.
If I’m saving yeast I don’t let any trub into the fermentor so how much more washing is necessary? I usually put the non-yeast percentage slider up to 15-25 to be on the safe side.
He goes over this in one of the podcasts, can’t remember which episode. Jamil says that the default setting on the slurry tab is for rinsed yeast allowed to compact in the fridge for about a week. The max (4.5 billion/mL) are what you get from wyeast/white labs. I don’t quite buy that your yeast is going to be 80% less compact than the white labs yeast, so I use somewhere between 3.5-4.5 billion/mL.
IIRC, Kai had a reference from one of those German textbooks of his of yeast cell count in slurry, and I thought it was to the high end of the mr.malty slider. I’ll see if I can find the post…
From NB forum:
[quote]I’m assuming about 3 billion cells/ml sediment. This number comes from 2 different German brewing textbooks.
But in the end I think your actual viable cell count will be +/- 20% anyway. If Jamil has different numbers than this is b/c he found different numbers with his propagation/fermentation conditions.
[/quote]
This would correspond to 3 billion cells/mL in the calc with 0% non-yeast %, which is about 3.4 billion cells/mL in the calc with the default non-yeast %.
I think you mean this one:
(Fermenting Lagers - German brewing and more)
At some point I’ll get around to measure the cells/ml myself. I would also expect it to depend slightly on the yeast strain but don’t worry too much about the exact number. I don’t think being off by 20% on the pitching rate is a problem.
Kai
Jamil goes over this in the Brew Strong: Repitching Yeast episode.