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Old 01-01-2013, 11:21 PM   #1
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Default Yeast Starter/Overpitching Question


Next weekend I'll be making a 1.095 Imperial IPA with WYeast 1056.

I'm making my first-ever starter for it. I'll need about 355 billion cells for this - I've been given two different numbers, 342 billion and 369 billion. I'm using the "intermittent shaking" method because I do not own a stir plate at this time.

Sunday Night (12/30) I made a 1.6L starter wort with a gravity of 1.044. Yeast manufactured date was 11/19/12 for a viability of 71% according to YeastCalc.com. I was expecting about 196 billion cells from this.

Tonight I made a step-up starter of 1.6L 1.050 wort. According to the calculator, I'm expecting 339 billion cells after this.

Now the question is... should I make another starter? YeastCalc says to expect 457 billion cells after a third step at the same size. If I make a smaller amount, say 1.0 or 1.1 liters, I can hit the 369 billion cells number.

I honestly think I'm "close enough for government work" with 339 billion, 91.8% of the optimal pitching rate, but can I get a second or third or fourth opinion?


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Old 01-01-2013, 11:39 PM   #2
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I would go with what you have, It's plenty of yeast.

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Old 01-02-2013, 01:55 AM   #3
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339 should be just fine.


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Old 01-02-2013, 02:29 AM   #4
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If you make more you can always save some for another batch!

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Old 01-02-2013, 12:59 PM   #5
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You should be close enough. Expect to be off by a factor of at least 2 using the calculators. You can also estimate cells by volume. 1-2 Billion cells per ml is a reasonable estimate for cells in a starter.

The viability by date on the popular calculators has been pretty far off in my experience. Yeast from Wyeast or White labs is more likely 90% viable worst case even after several months. Glycogen reserves might be low so it might take some time to build up the sterol content for cell permeability, but there are plenty of live yeast.

Both Mr. Malty and Yeast Calc are derived from the same set of experiments at White Labs. For these experiments a 1.036 wort was used. Because you are using a 1.044 wort you can expect about 20% more cell growth per step.

If I was going to guess, I would say you already have plenty of cells.


But the only way to really know is with a cell count:

Next time, as an alternative, you might consider using the known 100 billion cells in a smack pack and pitch that into a reduced amount of wort. After a day add the remainder of the wort.

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