Formulating a starter wort? (looking for a scientific/mathematical answer)

Kickass said:

Like wise is there a formula for how many billion cells I’ll need and how to determine that?

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NQ3X said:

Yes. You're looking for 1 million cells per milliliter of wort to be pitched per degree Plato.

How to figure it:

Degrees Plato are roughly equivalent to 4 points of specific gravity. Thus, 1.048 is as close to 12ºP as makes no difference.

5 gallons is as close to 19 liters as makes little difference (18.927). That's 19,000 milliliters.

Thus, for a wort of 12ºP you need 12 million cells per ml. 19,000 times 12,000,000 equals 228,000,000,000 or 228 billion cells for proper pitching.

I suggest you ferment your starter fully and harvest the slurry from the flask. 1 ml of fresh slurry contains about 1 billion cells. So, continuing our example, to inoculate a wort of 12ºPlato you need 228 ml of yeast slurry.

Make sense? All you need to plug in is the OG of your 8-9%ABV stout, and you can easily figure how much slurry to make with your starter setup.

Good luck!

Bob

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Kickass said:

I’m planning a double stout and was curious about formulating a starter wort. I’m looking for 8-9%ABV and will obviously be crafting a starter work for my yeast soldiers. I’m planning to use Wyeast activator Irish ale 1084

Is there a formula for determining the specific gravity of the starter wort I’ll need to start my yeast out for such a big beer?

Like wise is there a formula for how many billion cells I’ll need and how to determine that?

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bad coffee said:

Bob,
Suddenly it's all making sense. I don't know why, but the way you explain it makes it simple. I've even done the calculations on paper, and it didn't make as much sense as your post.

Thank you.

B

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