PurePitch viability and starting cell count equations updated

Discussion in 'Feature Requests' started by PNW Ale Project, Jun 13, 2019.

  1. PNW Ale Project

    PNW Ale Project New Member

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    Hey guys,
    Currently, when calculating my starting cell count for Whitelabs Purepitch yeast, I go to the QC website here:
    https://www.yeastman.com/Login/Public/Report/PublicLabQCResult.aspx

    I punch in the lot # and change the dropdown menu to homebrew purepitch, and that gives me an initial cell count in the packet.

    The next place I go is the viability website here:
    https://www.whitelabs.com/news/purepitch-shelf-life

    From here I can work out a percentage based on the percentages given and the time the yeast was manufactured. I know it isn't perfect but it is a lot more accurate than the current Whitelabs equation used in the software.

    For instance, I have a packet of WLP001 that was manufactured on 1/7/2019. The lot number is 1067653. In the current calculator, I have essentially no usable yeast.
    Using the above method, I see I have 2.23 billion cells/mL. It is a 40 mL packet so on 1/7/2019, I started with 89.2 billion cells. Using the viability percentage, I now have about 79% viability so I am actually starting with 70.468 billion cells.

    You can see the large disparity between the two numbers. Even just updating the percentages to better reflect the purepitch packet would be better than the current calculator allows.

    Just my two cents.
    Love the program and everything you do!
    Sean O
     
  2. Yooper

    Yooper Administrator
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    I'm trying to picture how this could work. It would involve only one manufacturer and only one set of yeast strains so I'm not sure how we could integrate it into the entire yeast library/pitching calculator.
     
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  3. PNW Ale Project

    PNW Ale Project New Member

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    The easiest way to make it work is assume each Purepitch has a starting cell count of 2.4 billion cells per mL. 40mL packet means each packet starts with an average of 96 billion cells. The next thing you could do, is as best as possible, use the viability page to develop some averages over time. It isn't exactly linear but at least it will be more accurate than the current calculator. Just put those under another drop down option for purepitch.

    The initial cell count isn't even that great of a deal, it is more the viability that would benefit people the most. It shouldn't be to hard to develop the equations for that.
    Again, just a suggestion.

    Thanks Yooper!
     
  4. Nosybear

    Nosybear Well-Known Member

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    What does White Labs say about pure pitch viability? I scanned the site briefly and didn't find anything other than a 4-month recommended shelf life.
     
  5. PNW Ale Project

    PNW Ale Project New Member

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    All I'm saying is the viability percentages used are from 7 years ago and the pure pitch viability is much much greater than the vials used to be.
    Per Whitelabs website:
    Average viability of PurePitch® pure liquid yeast over a period of six months:

    1 month - 99.21%

    2 month - 98.05%

    3 month - 90.26%

    4 months - 84.28%

    5 months - 79.35%

    6 months - 71.59%


    The current BrewersFriend calculator viability percentages are as follows:
    • Liquid yeast viability drops 21% each month, or 0.7% each day, from the date of manufacture. The assumption is the yeast viability drops in a linear fashion. In 4.75 months or 143 days, this calculator assumes the yeast is 100% dead (100 / 0.7 = ~143).
    • From the White Labs FAQ 11/2012: What is the shelf life of White Labs Yeast? Quick Answer: 4 Months. Long Answer: .... After 30 days in the vial, the viability of our yeast is 75-85%,...
     
  6. Yooper

    Yooper Administrator
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    We'll definitely think about this, and ways it could be implemented. We're open to ideas from others, as well!
     
  7. Nosybear

    Nosybear Well-Known Member

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    PNW: What's the source of your numbers? I was poking around on White Labs' site last night and couldn't find them. Anyway, I punched them into Excel and got the following chart:

    upload_2019-6-14_13-44-18.png

    Assuming 100% viability at packaging, you can model the yeast's viability using the equation shown. Note "X" is months! So you'd have to use "Days" divided by the average month length to use this equation to model the decrease in viability. And note the R-squared is very high so this would definitely be close enough for homebrew.

    I did find that White Labs lists the shelf life of their yeast at 4 months so they want to keep the viability at around 85% or greater. Again, in the "close enough for homebrew" range, the error of assuming 100% viability (I've been known to miss this step in the calculator), your error in pitch rate is 15%. I'd bet we'd be hard-pressed to detect the difference in yeast made with yeast at 100% viability and yeast made with 85%.
     
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  8. PNW Ale Project

    PNW Ale Project New Member

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    Nosybear, The links to the sites are in the original post. Here they are again though:
    https://www.yeastman.com/Login/Public/Report/PublicLabQCResult.aspx
    - This site is where the Lot number is entered and you can then see their specs for acceptable QC criteria.
    https://www.whitelabs.com/news/purepitch-shelf-life
    - This is where they posted their viability percentages for Purepitch
    Your chart looks great and I agree that the difference between 85 and 100% at packaging isn't that big of a concern, I would just use the 96 billion cells as a starting point since it falls right in the middle of their acceptable QC band.
    Hope this helps!
     
  9. PNW Ale Project

    PNW Ale Project New Member

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    @Nosybear did you see these links I posted earlier? I have a post pending admin approval I'm assuming due to the links in it but they're in the initial post.
     
  10. Nosybear

    Nosybear Well-Known Member

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    They reproduce so fast the difference there is negligible. If you have a copy of the latest issue of Zymurgy, Drew Beechum and Denny Conn address exactly this issue. I think where a lot of people early on get wrapped around the axle is that a lot of what is a good engineering solution for a very large brewery, pitch rate included, just isn't that important to us at homebrew scale. There's a big difference between a 24 hectoliter brew and our 0.24 hectoliter batches! The second link is where I found the data for the chart, the first isn't working for some reason. My take: If I'm Coors and interested in making exactly the same brew every time, getting pitch rate right is probably worth the effort, besides, I have lots of yeast, a state-of-the-art lab and some guy paid to count yeast cells in my slurry. For me at my scale, a few billion cells just doesn't make that much of a difference, an additional hour of yeast growth will more than make up for the difference. I use the yeast calculator, trust it, and make good beer. That's what matters to me.
     
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  11. PNW Ale Project

    PNW Ale Project New Member

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    I'm not sure if you are saying that updating the viability percentages isn't worth the time. If so, under that logic, why have a calculator at all? I would argue the difference between 0 and 70.5 billion cells (Taken from first post) is a lot more than negligible. I'm not asking them to change the calculator at all, just add that for Purepitch, they maybe add a dropdown selection and update the percentages, like what you've done on your graph. Brewing is largely process built and repeatability is important to a lot of us. The more accurate we can make tools, the better.
     
  12. Finn B

    Finn B Member

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    I heartily agree. Besides, cell count is far less important than yeast health, though of course you shouldn't ignore it. (I do not buy the Shaken Not Stirred method, which I think takes this too far, but that's another matter.)

    I use a stir plate, and I don't really need that calculator because I know that 1 liter (1.06 quarts) of 1.040 wort will give me 160 billion new cells. (Which I have learned from the calculator:).) Then I just add an estimated cell count for whatever yeast I'm propagating. An error there won't make much of a difference to the end result.

    (Of course I need to know how many cells I ought to have. The calculator is nice to have there. Or I use the table in How to Brew, p. 116, which gives me the same answers.)
     
  13. Nosybear

    Nosybear Well-Known Member

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    The biggest problem with homebrew and science writ large is that there's no money in researching homebrew. No one is going to fund research into production of 20 liters/5 gallons at a time! There are some hobbyists out there applying science to homebrewing (yes, Brulosophy, I'm talking to you) and they come up with some interesting finds from time to time but as an engineer, I'm interested in reproducibility, not a unique result. So most of our "knowledge" is gained through scaling down industrial processes, some of which are useful at our scale, some almost useful, some downright wrong. So in this case, it's the body of experience that is more useful than the body of knowledge, hell, I can make good beer and never make a starter! Just use dry yeast and scale up by sachets. Yeast grow exponentially so if you miss the initial pitch, you've caught up a couple of generations later and at the time you're catching up, the number of yeast cells is small.... I'll end the rant here.
     
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  14. Finn B

    Finn B Member

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    #14 Finn B, Jul 24, 2019
    Last edited: Jul 25, 2019
    They grow exponentially, yes, but they'll stop reproducing when the store of sterols/lipids they started out with - and which is not replenished - runs out, or rather reaches a critical level, even if there is fermentable sugar left. Then they start the hibernating process. So it is wrong to presuppose that they will just go on reproducing till they've compensated for the low number pitched. This is my issue with the Shaken, Not Stirred method. No matter how healthy your yeast is, you can't ignore the need for a certain population size.

    A quotation from dr. Clayton Cone of Danstar: "At each doubling it will split the lipids with out making more lipids (no O2). The first split leaves 2.5% for each daughter cell. The second split leaves 1.25% for each daughter cell. The next split leaves 0.63%. This is the low level that stops yeast multiplication. Unless you add O2 the reproduction will stop." (The source for this not available any more. I've got it from a Norwegian blog.)

    The rest of what you say here, is pure Truth;).
     
  15. Nosybear

    Nosybear Well-Known Member

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    Good reason to aerate/oxygenate the really big beers a second time.... I agree with you that a serious under (or over) pitch will detract from the beer. I know they won't reproduce indefinitely but it's a case where close is good enough.
     
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  16. BOB357

    BOB357 Well-Known Member

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    Not that I'm a yeast Guru, but aren't those numbers based on, "proper handling and storage"? IMO, that would pretty much make them iffy unless you're ordering directly from the lab and receiving the yeast at a reasonably cool temperature.
     
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  17. Finn B

    Finn B Member

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    Definitely! Based on my own experiences - which of course don't prove anything - I do not put much trust in that 6 month guarantee. I've had a couple at 6 months or just a few days past which were quite simply dead. No sign of life even after several days on the stirrer. And I buy mine directly at the store, and I trust the routines of that store. To be fair I've had 6 months olds that were OK, too.

    Imperial do not guarantee a shelf life longer than 3 months, and I trust them a lot. Seems you can rely on their yeast to perform right up to that date. (I've had yeast from them well past those 3 months, and it was still excellent.)
     

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