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Old 03-12-2013, 03:50 AM   #1
bradfordmonk
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Now this just got confusing...why are there all of a sudden two different stir plate options?
  1. Stir Plate (K. Troester)
  2. Stir Plate (J. Zainesheff)


And I get completely different sets of numbers for each. See below...Anyone know what the difference is...aside from numbers; and which should I go with?
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Old 03-12-2013, 05:10 AM   #2
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Kai shaking up the home brew world? Nice going dude.

 
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Old 03-12-2013, 06:57 AM   #3
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Growth rates are not fully researched jet, that is the main reason why different authors states different results.
Yeastcalc is using results from 3 common resources:

Chris White researched growth rate at non-stirred starter, results are published in "Yeast".
Jamin Zainasheff then multiplied those results to get growth in stirred starter, I think he uses 2.5 as multiplier.
Kai Troester researched growth rate in stirred starter as function of growth per gram of extract.

That said, when using stirred starter you will make slightest mistake if you use Troester's growth rate. I think it is the best resource that we have at the moment, but I hope that further experiments will be made on this topic.
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Old 03-12-2013, 09:16 AM   #4
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Any idea as to which one was used before when there was only 1 option?
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Old 03-12-2013, 11:47 AM   #5
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Kai Troester has published information on this subject here.


Woodland Brewing published information related to yeast growth vs sugar concentration here.

On a related note, Woodland Brewing has also published viability test results, here, which call into question the viability calculations being used as well.
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Old 03-12-2013, 02:02 PM   #6
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So you think I should go with the Troester option of Stir Plate? I would like to believe that, as I'd only have to make a 1 step starter @2L.

but the numbers are so widely different. So its tough to say...i do now when I've made yeast starters with step starters (I assume using the Zainesheff stir plate model being what was defaulted by yeastcalc before) that my fermentations were very vigurous and fast...maybe a dig that I had alot more cells than the calculator was estimating? Possibly?
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Old 03-12-2013, 02:39 PM   #7
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Kai's stirplate data la used in conjunction with sugar concentration data on brewersfriend also

 
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Old 03-12-2013, 06:59 PM   #8
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Quote:
Originally Posted by CloverBrew View Post
Kai's stirplate data la used in conjunction with sugar concentration data on brewersfriend also
not sure what you mean. Are you saying that's what the option Troesters accounts for. If thats the case this seems better.
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Old 03-12-2013, 07:04 PM   #9
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Thanks for the mention Rauliii.

Use Kai's equation. Especially if you let it ferment to completion. His equations were produced from stirred starters instead of scaling still starters. It also more closely follows Ballings observation.

If you really want to dial in the measurement of cell growth without a microscope there are some calculations that can be done based on starting gravity, and final gravity as measured with both a refractometer and hydrometer. But for all practical purposes, Kai's equation will get you plenty close.

On my blog is a comparison of various calculators and actual growth of over 50 starters. These were all still starters, but it may be of interest.

http://woodlandbrew.blogspot.com/201...revisited.html
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Old 03-12-2013, 08:13 PM   #10
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.

 
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