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I've harvested some yeast from a commercial bottle (Maine Beer Company's Mo Pale Ale) and stepped it up to a 1L size. I'll be making a pale ale at ~1.055 OG and everything I read indicates I'll want roughly 180-200 billion cells and that about 1L of starter should get me there. But that's 1L of starter built from standard starting points (like liquid vial) so I don't really know if my 1L starter is remotely in the right ballpark.

Here's what I've done:

  • Added slurry from one beer to 250ml starter wort (25g DME, 250g water)
  • 2 days: Observed thin layer of bubbles
  • 3 days: Doubled the starter (added another 250ml, total 500ml)
  • 3.5 days: Observed very nice looking krausen
  • 4.5 days (36 hrs since last feeding): Doubled the starter (added 500ml, total 1L)

My plan is 24 hours after the final feeding to refrigerate it for 2-3 days until I brew, decant most of the liquid, and pitch the yeast.

Does this sound like I will reasonably hit my ballpark for cell counts? Should I look for any particular volume of settled-out yeast to validate approximate cell counts?

Update I doubled again to a total of 2L of starter wort. After another day I refrigerated it 2 days before brewing and I poured out most of the liquid. I brewed a pale ale and from what I can tell fermentation was strong. I ended up with 5.9% ABV, 81% attenuation.

Ryan Silva
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2 Answers2

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Sounds about right

Most yeast manufacturers equate 35-50ml of clean yeast slurry to 100-200 billion cell count.

Only way to really know for sure is to do a cell count.

Insurance in volume: I would repeat your step starter process and make a second 1000ml starter, using a few eye droppers worth of the new yeast you grew. Just to make sure I have enough, and possibly to set aside and store the culture for future use.

Decant your starters to see how much slurry you get. If you get 35-50ml yeast this would be the equiviant to pitching a single commercial wet pack.

Personally I would shoot for 100ml+ for a OG of 1.055

Evil Zymurgist
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  • Thanks for the reply. I just put it in the fridge (this morning was 24 hrs from last feeding). If I make a second starter, I'd decant and use some of the second if the first doesn't have 50ml worth of slurry? What if I just let this one settle, decant, then re-feed with another 1L? How long does it take for yeast to fully settle in the fridge? – Ryan Silva Apr 05 '18 at 12:46
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    @Ryan I would start the second one now. To step a starter the total volumes need increased or the yeast decreased, or the yeast Just feeds without much growth. Usually yeast will drop out in 12-24 hours if at terminal gravity if there's still sugars it will still try to feed/make cO2 making it hard to get them to drop out. – Evil Zymurgist Apr 05 '18 at 13:05
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    There's actually couple easier ways to get more yeast from what you have now, without stepping from a small sample. You can split your 1000ml into two 1000ml flasks and add wort. If You have a large flask you could just step up again to more volume. – Evil Zymurgist Apr 05 '18 at 13:09
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    I found a 4 qt container so I just doubled it again. – Ryan Silva Apr 06 '18 at 22:16
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According to yeast pitch calculators, the start amount of yeast is not that important. Adding the wort in steps helps to cultivate the yeast healthy. My guess it will be fine but you can always check how many ml of slurry you have after refrigeration and determine the amount of yeast.

JesseB1234
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  • I haven't found consistent answers for yeast count based on ml of slurry after decanting (that's part of my question). Mr. Malty calculator (not sure if I'm using it correctly) says 60ml if I drag "yeast concentration" closer to the "thick yeast" side. – Ryan Silva Apr 05 '18 at 11:52