How to use the White Labs QC report to get an accurate cell count of your yeast

[jvector]

Hey everyone,

Forgive me if this is a repeated topic, but a quick search didn't find anything similar.

Yeast viability (ie, healthy cell counts) is an important part of homebrewing. Specifically, it's important to pitch the correct number of cells into your wort by creating properly sized starters (FWIW, I'm ignoring the vitality argument for now). There are numerous calculators that help you figure out your starters, like Mr Malty's, Homebrew Dad's, and the one right inside Beersmith.

These calculators generally use the following inputs to calculate your ideal starter size(s):

• Original gravity of your wort
• Date of yeast manufacture (assuming some loss of viability per month, usually 20%/mo)
• Original cell count (usually 100 billion for liquid, and 200b for dry)

Regarding the third assumption, original cell count, it occurred to me that we do not need to make this rough assumption when we use White Labs yeasts (or Yeast Bay for that matter, which is produced by White Labs). Every tube of White Labs yeast has a Lot number printed on it, and they graciously provide all the quality control (QC) information for free. Follow these steps:

1. Go to https://www.yeastman.com/Login/Public/Report/PublicLabQCResult.aspx
2. Type in your Lot Number (In my example, I have a tube of Yeast Bay Wallonian Farmhouse, lot number 1027066)
3. Look at the row titled "Cell Counting" (Example, this lot says 1.68e9, which is 1,680,000,000 cells/mL)
4. For the old plastic hard tubes, multiply by 35 mL; for the new PurePitch, multiply by 40mL (Example, 1.68e9 * 35 = 58.8e9 = 58.8 billion cells)
5. Note the lab test date (Example, 7/2/2016)

Done.

Now you have much more accurate information to plug into your yeast viability calculator. Looks like I need a multi-step starter.

Without this method, I would have underestimated my original cell counts by almost half (100b versus 59b).

For what it's worth, White Labs aims for 1.5e9 to 3e9 cells/mL for each batch. A few brew days ago I got a batch that was over 4e9 cells/mL in a PurePitch, and reasonably fresh, so I had over 150b cells on brew day. Don't just assume 100b!

Has anyone else used this method? While the 100 billion cell assumption might get you close, the QC information is free. Why not use it?

Thanks for reading. Any thoughts?

 

[Pie_Man]

Thank you, this helps.

I use yeastcalculator. WIth the initial cell count from White Labs, I can now edit the "Initial Cell Count" variable in YC to more accurately determine my starter size.

Example:
The White Labs QC report for my vial stated a cell count of 2.8e9/ml (2.8 billion/ml). There are 40 milliliters in a vial, so 2.8 * 40 = 112 billion cells as my initial cell count.

 

[RM-MN]

Good info. Now go back and figure out yeast viability. It will vary by a huge amount depending on conditions during shipping and storage. Mr. Malty estimates 20% loss per month while Woodland Brewing's experimentation shows that with good storage conditions that loss is only about 1% per month. Figure out the conditions that the yeast went through all the way from White Labs to your hands and reconcile that with the two viability estimates.

http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.html

Now with all that in mind, forget about it all, aerate your wort very well and a very underpitched yeast will reproduce in the wort and make a fine beer anyway. After all, if Gordon Strong, a Ninkasi Award winner, is satisfied with pitching a single smack pack to a lager when the calculators say you need at least a 2 liter starter, there must be something wrong with all the calculations.