Yeast cell count without a microscope

[nathank]

Hey guys, I know it's a bit of a stretch but I was wondering if anyone would be able to help me out with some kind of a guess here.

I just did my first harvest of Lutra Kveik from a 10L batch of seltzer that used 5.5g of yeast, and was just wondering if anyone would have any idea of how many cells I'd have left now (if I did it properly).

Omega claims 20 billion cells per gram, so would have been about 110 billion cells in the original brew.

 

[VikeMan]

Step By Step:

- Measure the volume of the slurry.

- Estimate the Density: A very thick, compacted slurry might be about 4.5 Billion cells per milliliter. An 'average' density might be about 2.4 Billion cells per milliliter. A thin slurry might be about 1 Billion cells per Milliliter.

- Multiply the slurry volume in mililiters by the estimated density to get a first whack at an estimated cell count. But then...

- Estimate the Non-Yeast percentage: This is the percentage of your harvested yeast slurry solids that were something other than live yeast (such as hop particles, lipids, dead yeast, etc.) when harvested. An average recommended value for this might be 15%. If you rinse your yeast, your value may be closer to 0%. If you are pitching directly onto a yeast cake, your value might be closer to 25% or even 50%.

- Multiply your first estimated count by (1 - Non-Yeast %) to get a new estimated cell count. But then...

- Subtract about 0.7% of the estimated cell count for each day the harvested yeast has been dormant, to get a final estimate of viable yeast cells.

 

[hottpeper13]

I don't know if this is right or wrong but this is what I do.

Knowing the amount of cells you pitched, the OG of wort, the amount of wort,I input that into Brewdads yeast starter calculator, and that will give you the amount of replication (wanting 3-5) and ending cell count.

 

[McMullan]

If you're interested in cell counts get a microscope. I use a microscope and a densitometer (suspension turbidity meter) designed for yeast cells in the lab, but when it comes to brewing I just pitch as much healthy yeast as I can lay my grubby hands on. A microscope doesn't need to be expensive. My kids' toy microscope is actually good enough and it plugs into a PC.

 

[nathank]

Step By Step:

- Measure the volume of the slurry.

- Estimate the Density: A very thick, compacted slurry might be about 4.5 Billion cells per milliliter. An 'average' density might be about 2.4 Billion cells per milliliter. A thin slurry might be about 1 Billion cells per Milliliter.

- Multiply the slurry volume in mililiters by the estimated density to get a first whack at an estimated cell count. But then...

- Estimate the Non-Yeast percentage: This is the percentage of your harvested yeast slurry solids that were something other than live yeast (such as hop particles, lipids, dead yeast, etc.) when harvested. An average recommended value for this might be 15%. If you rinse your yeast, your value may be closer to 0%. If you are pitching directly onto a yeast cake, your value might be closer to 25% or even 50%.

- Multiply your first estimated count by (1 - Non-Yeast %) to get a new estimated cell count. But then...

- Subtract about 0.7% of the estimated cell count for each day the harvested yeast has been dormant, to get a final estimate of viable yeast cells.

Thanks mate I'll follow this and have a stab in the dark.

If you're interested in cell counts get a microscope. I use a microscope and a densitometer (suspension turbidity meter) designed for yeast cells in the lab, but when it comes to brewing I just pitch as much healthy yeast as I can lay my grubby hands on. A microscope doesn't need to be expensive. My kids' toy microscope is actually good enough and it plugs into a PC.

One day I'll buy a microscope and do it properly.