[dak0415]

Forgive me if this has been covered elsewhere.  Which yields more yeast cells, a single 4 liter starter, or 2 2liter steps with a chill and decant in between?  This is assuming using a stir plate.

Tom?

[tschmidlin]

That I don't know without testing

Theoretically it'd be the same, assuming you have sufficient O2 and the same amount of sugar.  But that doesn't mean that's how it would turn out.  I could imagine reasons for it to go either way.

[dak0415]

Using the 4 liter starter, would there be an advantage to hitting the starter with a minute of pure O2 daily.  I use 6000ml Erlenmeyer flasks with a foil cap.

[narvin]

Wyeast gives a distinct advantage to 2-step starters.

http://www.wyeastlab.com/hb_pitchrate.cfm

[tygo]

There was a thread on this a little while ago that discussed this (and also linked to that Wyeast calculator as well)

http://www.homebrewersassociation.org/forum/index.php?topic=2534.msg29558#msg29558

My understanding from this and other sources is that multi-step starters do produce more growth.  Taking it a step farther, from the discussions and sources I've seen I've gleaned that identical volume multi-step starters will give you more yeast.  So if you do a gallon starter, chill, decant and do another gallon you'll end up with an increased cell count, the growth rate is just lower.

[tygo]

Wyeast gives a distinct advantage to 2-step starters.

http://www.wyeastlab.com/hb_pitchrate.cfm

Is that calculator assuming 100% viability?

[tschmidlin]

Wyeast gives a distinct advantage to 2-step starters.

http://www.wyeastlab.com/hb_pitchrate.cfm

I must be doing it wrong, because when I use a single step 1-gallon starter with a stir plate it tells me the final concentration in that starter is 121.69 million cells per ml.  When I do two steps that are each .5 gallons, it tells me it's at 90.15 million cells per ml.  Same total volume, more cells in the single step than the 2-step.  Am I missing something?  Also, the calculator is not decanting in between pitching, it is assuming you are adding more wort.  Anyway, based on how I'm using the calculator the 2-step seems to be at a disadvantage.  What am I doing wrong?

[tygo]

Yeah, you're right.  That's interesting.  But try doing a three step starter using a stirplate at 0.5 gallons, 1 gallon, and 1 gallon.  You get 90.65 million cells/ml.  If you put in a single 2.5 gallon starter you get 72.37.

It's not a very useful practical calculator since, as you point out, it doesn't allow for decanting.  But interesting as an example.  If I could find a good source for growth rate functions I think I could build a spreadsheet to approximate the cell counts.

[denny]

I must be doing it wrong, because when I use a single step 1-gallon starter with a stir plate it tells me the final concentration in that starter is 121.69 million cells per ml.  When I do two steps that are each .5 gallons, it tells me it's at 90.15 million cells per ml.  Same total volume, more cells in the single step than the 2-step.  Am I missing something?  Also, the calculator is not decanting in between pitching, it is assuming you are adding more wort.  Anyway, based on how I'm using the calculator the 2-step seems to be at a disadvantage.  What am I doing wrong?

Maybe you're not doing anything wrong.  Maybe it's time to email Greg and ask him what's up?

[tschmidlin]

Maybe you're not doing anything wrong.  Maybe it's time to email Greg and ask him what's up?

I think you're right, there seems to be a mistake in the formula they are using.  When I use a 1 gallon single step starter, the second step says 121.69 M cells/ml.  If the second step adds 0.1 gallons and you add that to 5 gallons of wort the total volume is 6.1 gallons with 16.26 M cells/ml.  But if instead you use 0.0001 gallons for the second step, your final volume is 6.0001 with just 0.83 M cells/ml.  That can't be right.  I'll email Greg.