I have 1cm of thick slurry in a standard pint mason jar. I need to know roughly how many cells are there so I can plug it into yeast calc and find out what size starter I need. It is Brett L and Lacto blended. Jamils slider doesn't really help me since I need to know how much I have, not how much I need. I looked for some sort of visual chart that shows roughly how much is there but couldn't find one. Thanks for the help.
What about this calculator? You basically did a 500 ml starter (that's roughly 16 ounces). http://yeastcalc.com If you go down to step 1 and change the volume starter to .5, it adjust the numbers.
It is slurry from a brewery, with maybe 4 cm liquid on top of the 1 cm of slurry. No starter to make it. The slurry is from the from a just finished fermentation as it was being pitched to a new batch. The yeast calculators don't help since I need to know how many cells I have to start with, which I don't know.
Hmmm.... well to quote from Yeast: "...Once you harvest the yeast from either the top or bottom, you will most likely have between .8 billion and 2 billion cells per milliliter." I know that doesn't really help given the range. Do you have the book? It has some info on estimating on page 123-124. Weight and actual microscope samples seem the route as opposed to thickness of slurry. Someone else on here more educated on yeast could probably add more as well. Second thought, the brewery certainly keeps track of such info, could you not ask how many cells per milliliter they typically have in their slurry?
That is helpful. I will ask the brewmaster about how much should be in a ml of slurry. Now, the question becomes how many ml of slurry are in 1 cm of a pint mason jar?
I have the same burning question as the OP and can not find it addressed. We are looking for yeast cells in a given volume . . . this gives a starting point to see what we are working with. I converted 1cm of yeast in a standard pint jar to 3.22 cubic inches or 52.7 milliliters. If the quote from Yeast above is correct, this equates to 42 billion to 105 billion cells. This is a wide range, but at least it's something. My guess is these are believable numbers, but does anyone else have experience with this type calculation?
I like the pictures at the bottom of this wyeast site: http://www.wyeastlab.com/hb_pitchrates.cfm Basically using % solids as an estimate of yeast cell density. 50% solids looks to be about 100 billion cells / mL; if you have 1 cm slurry over 4 cm liquid, or 20% solids, that would be about 100*20/50 = 40 billion cells/mL. Based on the diameter of your jar you can estimate total # of cells you have. The tricky part is viability and purity; you may want to pitch a bit more than what you'd calculate for 100% viability; wyeast is recommending 1.5 to 2x as much. Plus, of course, you've got lacto and Brett, at who knows in what ratio or live and dead cells. But - it is a start. You have to start somewhere!
This seems to address the problem. In my calculations I ignored the liquid (no yeast?) and figured the volume of the solid only. If I understand Wyeast correctly, the boost of 1.5 - 2 times normal pitch rates for harvested yeast is just a WAG to make sure there is enough. When making a starter, you will know pretty quickly if the yeasties are willing to co-operate. But all the yeast calculators depend on an input of the number of cells from your slurry. I suppose the 1.5 - 2 fudge factor is insurance you have enough. Anyone have examples they would like to share?
I think it's important to remember that this is all ballpark, even under a microscope. For me, the biggest factors are having fresh yeast--or making a big starter--and proper fermentation temp to help the yeast do their thing.
EDIT: 50% solids = 1.0 e9 cells/mL = 1 billion cells/mL, 20% solids would be 400 million cells/mL. Stupid scientific formatting.
