Author Topic: Pitching Rate Calculation Error  (Read 4048 times)

Offline Ghosttrain

  • BeerSmith Apprentice Brewer
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Pitching Rate Calculation Error
« on: December 31, 2011, 06:42:45 PM »
Reposted from the brewing discussion forum since there may be an issue in the Beersmith yeast calculation that needs to be investigated.

Using the Yeast Starter Tool for a 5.25 Gallon batch with an OG of 1.067 both BS2 and MrMalty calculate ~242 Billion Cells.   
Using Liquid Yeast packaged on 11/6/2011 both tools estimate ~67% Viability. 

Now when you get to the calculation for the size of the starter in BS2 without a stirplate the internal calculation of the number of packs needed without a starter appears to be incorrect.    With the above inputs BS2 suggests that 6 yeast packs are needed which it 2 times as much as is really needed

6 packs x 67 Billion cells / Pack = 402 Billion cells

The ideal pitching rate is 242 Billion cells.   

The calculation then suggests that 2 vials in a 3.09 Liter starter is required which is about 1 L more than necessary to achieve a 1.86 growth factor.

Would you take a look at the internal calculations in BS2?    If there is a conversion factor error or an incorrect table lookup that could impact the calculation of the starter size needed with a Stir Plate.


Offline bschoenb

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Re: Pitching Rate Calculation Error
« Reply #1 on: March 03, 2012, 06:01:32 PM »
I agree:  I use a Stir Plate and the difference between Mr Malty and BS2 is HUGE.    I know that Brad posted he was going to talk to Jamil about this earlier?

It seems like the Growth Factor is perhaps the difference between both; I'm not even sure what the Real Growth Factor is for Yeast on a Stir plate.  2.66? or what?

Offline Myk

  • BeerSmith Grandmaster Brewer
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Re: Pitching Rate Calculation Error
« Reply #2 on: March 04, 2012, 01:29:31 AM »
Are you talking about the yeast starter tool in the recipe or from the tool tab?
I found the one from the tool tab seems to be very close to MrMalty. It's the in recipe one that is way off.