Author Topic: What volume of washed yeast to pitch into 5 galon brew?  (Read 161 times)

Offline MarkWebb

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What volume of washed yeast to pitch into 5 galon brew?
« on: September 09, 2018, 12:54:30 AM »
I have watch a few YouTube's on yeast washing. They end with yeast cakes in mason jars. I'm interested in the next step i.e. how much of the washed yeast cake to put into your next 5 gallon brew. How does one calculate this?

Offline Oginme

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Re: What volume of washed yeast to pitch into 5 galon brew?
« Reply #1 on: September 09, 2018, 06:00:37 AM »
Always a fun task.

I used several parameters for figuring the amount of rinsed slurry to pitch into a batch.  You need to look at the density, color, and cleanliness of the yeast.  If I see a some trub left in the yeast, I will apply a percentage factor based upon how much of the yeast cake is yeast cells vs trub.  I also add a color factor based upon the color of the yeast slurry.  If the yeast is not bright white or off-white, I discount the amount of viable cells further. 

Then I figure that a compacted yeast cake generally contains around 4.5 billion cells per ml.  I then apply a factor for how dense the yeast cake is, if it is not compacted, and then the factors I outlined above.  This will give me an approximation of how many cells per ml of slurry I have and I divide the number of cells I need for the recipe by that number to give me the ml of slurry to pitch.

It takes some time and experience to figure this all out, and don't be too afraid of over pitching a bit to be on the safe side. Realize that there is a pretty wide window of yeast cell counts that will work just fine.  Generally, the higher the gravity of the recipe I am pitching into, the more I 'underestimate' my slurry cell count leading to a slightly higher pitching rate.

The last few years, I have started doing actual cell counts and confirmed my educated guesses outlined above as being OK. 
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