Yeast cell counts

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jmf143

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Jamil had this on mrmalty.com:

Pitching a Wyeast Activator pack gives the following results within 12 to 18 hours:

1 liter starter = about 150 billion cells
2 liter starter = about 200 billion cells
1 liter starter, then pitched into 4 liter starter = 400 billion cells

Anyone know what the numbers would be for a Wyeast Propagator?
 
From wyeast's site faq:

6. Do I need to make a starter for an Activator?

No. The Activator is designed to deliver professional pitch rates (6 million cells/ ml.) when directly added to 5 gallons of wort. ( <1.060 at 70 degrees). However, if a package is slow to swell, suspected of being mishandled, or if the date is approaching the six month shelf life it is a good idea to build the culture up with a starter. High gravity or low temperature fermentations require higher pitch rates. This can be achieved with inoculating with additional packages or making a starter.

Edit: I should have done the math just in case, the packs have this listed on them:

The Activator&#8482; has a minimum of 100 billion cells of pure, ready-to-pitch yeast, plus an internal nutrient packet. The Activator&#8482; is designed to inoculate five gallons of wort (up to 1.060 SG) providing the pitching rate recommended by professional brewers.
 
That doesn't answer his question at all. The Propagator packs have way less cells - I think 1/3 - than an Activator. I don't know enough about yeast reproduction to say exactly what you'll need to do to get from 33 billion cells up to wherever you're going, but I don't think 18 hours is enough time to do it in.
 
Sorry bad headache today... totally misread... from wyeast's site on the PROPAGATOR.
The Propagator&#8482; package contains a minimum of 25 billion cells in a yeast slurry. This volume is not adequate for direct pitching into 5 gallons of wort and requires a 1-2 L propagation step prior to brewing

both of which took me 3 seconds on wyeast's site... :)
 
Very true. I imagine he was looking for more pointed information, but didn't give us anything else to go on.
 
Sorry about the confusion - thought the questions were clear. What would a Propagator grow to if pitched into a 1 liter starter? A 2 liter starter? A 1 liter starter that was then re-pitched ("Stepped up") into a 4 liter starter?
 
Set the viability to 25% in the PRC (don't calculate by date) to see how big a starter you need.
If you want answers to how much you will get if you have 1 liter or 2 liter starters, you need to play with the numbers in the calculator (usually enough just to play with OG)
 
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