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I have been playing around with yeast culturing for a little bit and I think I have reached by goal. I have yeast stored in 10 ml vials in sterile water. I use a couple of drops on a slant to start the growth. In 3-4 days, I have a flourishing garden of yeast. By my very crude estimates, I get about 500 cells on the slant and end up with about 500 million or so at the end of 4 days. That works out to about 10 doublings. I then transfer to 10 ml wort, 100 ml wort, and finally either 1000 or 1600 ml wort. (I still working out the final numbers.) At the end, I estimated about 20 ml of yeast, and by my estimates that should be about 160 billion cells.
Attached is my XLS worksheet for stepping up. I have plotted the data from White and Zainasheff and used XLS curve fit to get an equation. I know that the pitch rates that are typically used in culture and much lower than there data, but it is the best I had. The worksheet is not set up for public distribution and I seem to change something every time I play with it but it is a place to start and you can tweet the numbers anyway you want.
A filed for observed yeast concentration would be nice, some people have a hemocytometer and scope. With an observed concentration, growth estimates would be far more accurate than estimating the starting concentration.