Estimate Cells in Washed Yeast?

[junior]

Hi all,
I usually make a 1liter starter with 50ml of two-four month old washed yeast slurry, put in refrigerator, decant then step it up with a 2liter starter, put in the refrigerator until settled and decant then pitch into 5gallon 1.066 and have had good results, usually 80-85% attenuation. I am trying to estimate the amount of viable yeast cells in my washed yeast (50ml). I was playing around with Mr.Malty and other google searches and came up with and estimate of 20 billion cells per 50ml of four month old slurry, that would mean I am pitching 80-billion cells with my two starters. Obviously this cannot be correct because Mr.Malty calls for 228 billion cells.

 

[junior]

Sorry for the post,
I think this is what I was looking for.

https://www.homebrewtalk.com/f163/calculate-washed-yeast-416297/

It's all a bit of guesswork, but you can get a ball park estimate. Since the yeast has been washed, the concentration is going to be close to maximum and the non-yeast percentage is going to be close to the minimum. Mrmalty's concentration slider max's out at 4.5b cells/ml, so just go with that. 4.5b/ml x 140ml = 630 billion cells (give or take - I'd round it down to 600b). Next, enter the viability date (I'd just go with a week after it was pitched in the batch you washed it from) and multiply 600 x the viability percent and that will get you a close approximation of how many viable cells you have.

 

[tagz]

4.5B is a bit higher than I have seen. 1-2B per ml is the most common figure I see.