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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Estimating Yeast Cell Counts in Fresh Starter
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Old 02-17-2013, 01:04 AM   #61
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Originally Posted by tagz View Post
Great thread. I have a question about Woodlands latest blog post. Hope you don't mind me tacking it on here. Woodland discussed an equation showing the number of cells produced as a function of sg and fg. Seeing as most people pull their starters after 24 hours, are we not getting the optimal number of cells out of our starters? I assumed most reproduction occurred during the lag phase, but the numbers seem to indicate that reproduction chugs along until you hit fg.

Also, I've never really measured the sg of my starters. Do most starters hit fg after 24 hours?
It would be good to hear what others think about this as well.
(here is a direct link to the post for anyone interested: http://woodlandbrew.blogspot.com/201...nction-of.html )

This is something I have been investigating and am working on some posts that might help illuminate some of this. In short, it's dependent on a number of factors, but given some constraints you can get a pretty good estimate. For a starter propagated at room temperature with an inoculation rate of about 50 million healthy cells per ml and a gravity of about 10°P (1.040) It takes about 4-6 hours for propagation to begin. In the first 24 hours half of the cells are generated. By 48 hours nearly all of the cells have been generated.

Feel free to comment on the blog with questions directly related to it. I'm normally pretty quick about replying.
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Old 02-17-2013, 03:48 PM   #62
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Seeing as most people pull their starters after 24 hours, are we not getting the optimal number of cells out of our starters?
This is very yeast strain-dependent and also yeast age-dependent. Some strains grow fastest that others; and the aging of culture also influence the generation of new cells in a short time (older cells = more time in starter)

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I assumed most reproduction occurred during the lag phase, but the numbers seem to indicate that reproduction chugs along until you hit fg.
Yeast division occurs during exponential phase and not during lag, which is an adaptation phase to new culture conditions. Long lag phases indicate that the yeast initial culture is too old or that starter conditions are not adequate (too much high/low temperatures, too much high/low SG of wort, etc...)
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Old 02-25-2013, 12:31 AM   #63
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It would be great if this entire thread were rewritten with everyone using the same order of magnitude definitions. Preferably based on base 10 and exponentials as defined a few thousand years ago.

(10^6 as a "million," 10^9 as a "billion," etc, etc....)


Cheers!

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