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Old 02-06-2013, 12:17 AM   #1
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Default Estimating Yeast Cell Counts in Fresh Starter

I've just started working on building a yeast bank and I'm having a hard time approximating yeast cell counts.

I took a White Labs vial manuf 09 Jan 13 and made a 3.8L starter. Yeast Calc and Mr Malty tell me that I should have 375m cells afterwards. So I cold crashed and decanted, sworled the mixture like crazy to make it as unform as possible and poured into 8.25 40ml vials. 5 vials went into the fridge, and the other 3.25 went back in to be stepped up for next weekend's brew.

The problem is that I'm comparing them to the Wyeast graphic below and coming up with odd numbers. I should have about 45 billion cells in each vial, but my vials look closer to the middle one (87 billion per vial).



What am I doing wrong? There's no way the picture is correct and I actually made 718 billion cells.

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Old 02-06-2013, 06:08 AM   #2
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A lot depends on how compact and how fresh. It looks like the WL is estimating 3 billion cells per mL based on a very low non-yeast percentage, no aging, and very dense cells. How dense is yours? How old? How much non-yeast is in there? Fiddle around with those numbers on mr. malty repitch from slurry tab until you feel comfortable with the numbers.

This is from the yeast book author:


If you've brewed more than one batch, I'm sure you've noticed that there is a huge pile of yeast in the fermenter at the end. If (and that is a big 'if') you've got excellent sanitation all the way through the process and have provided proper yeast nutrition (including O2), you have a gold mine of healthy yeast ready to reuse. Of course, you don't want to reuse the whole thing. I know a number of people dump a new batch on top of the yeast cake, but you're not going to get the best beer that way. Yeast do need some growth to result in the right kind of ester profile, etc. While too big a pitch is better than too little, it is pretty easy to figure out how much you need and pitch just that.

There are about 4.5 billion yeast cells in 1 milliliter of yeast solids (solids with no excess liquid). According to Fix, in a slurry, only about 25% of the mass is yeast solids. Of course, if there is a lot of trub in there, you have an even lower percentage of yeast solids. The bad thing is that you can't tell how viable that yeast is, unless you have the equipment to properly test and count it. So this is where it gets a little bit like black magic. There are a number of factors that affect the viability of a given pitch of yeast. How old is the yeast? How stressful was their last fermentation? Have they had the proper environment and nutrients for successful reproduction or are they too scarred and tired to go on?

When the yeast is fresh and healthy off an previous batch, viability is maybe around 90%+. It goes down from there fairly quickly without proper storage and it also really depends on the strain of yeast. Unless you're going to get into testing viability, you're going to need to make some educated guesses and keep good notes on the results. This is where being a yeast psychic really helps. Start in a range of 80 to 90% viability and you probably won't be too far off. Use the Pitching Rate CalculatorTM to help figure out how much of that yeast you need. If your yeast viability is much lower than 90%, you should probably toss the yeast. If you really want to use it, you might consider pitching it in some starter wort to get the still viable cells active. When they're in solution, decant that active part of the starter into another vessel, hopefully leaving the dead cells behind.

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Old 02-06-2013, 01:52 PM   #3
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Quote:
Originally Posted by theveganbrewer View Post
A lot depends on how compact and how fresh. It looks like the WL is estimating 3 billion cells per mL based on a very low non-yeast percentage, no aging, and very dense cells. How dense is yours? How old? How much non-yeast is in there? Fiddle around with those numbers on mr. malty repitch from slurry tab until you feel comfortable with the numbers.
Density? Don't have measurement tools for that.

Age? About 100 billion packaged 09 Jan 13 at White Labs, the other 275 billion a few days old.

Non-yeast? Well, there's no hop trub to speak of. I suppose there could be some proteins from the DME, but it's impossible to tell if there is and how much.
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Old 02-06-2013, 02:12 PM   #4
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I'm starting to think that weighing might be a better answer. You wouldn't have to wait for strong yeast compaction to measure. Notice the picture above has % of yeast solids by volume underneath the

I know the OG was 1.040. I can take the FG with a refractometer, correct for alcohol, and know the true FG. At that point I'd know the weight of an empty vial, the gravity of the spent wort, and the weight of the full vial. It's a pretty simple formula to figure out the ratio of yeast to spent wort from there.

Or, we can try it this way:

Quote:
Originally Posted by Wyeast
Slurry can be harvested based on volume or weight. 1L (1 quart) of yeast slurry (40% yeast solids) weighs approximately 1.1 Kg (2.4 lbs.). The following guidelines will deliver the appropriate pitch rates.
The only problem is those figures seem to be based upon harvesting the cream from a conical, so it might not be applicable to me, as I have no trub.
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Old 02-06-2013, 02:44 PM   #5
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Just pulled the vials back out of the fridge. We're at about 36 hours cold crash now.

Compaction increased overnight. I'm looking at closer to 12-15 of yeast solids now, which seems closer (75b-93b) but still not quite there. The spent wort clarity is starting to approach that of the picture, though still slightly cloudier.

Trying to determine the ml capacity of the pictured vials. I think they're Wyeast Nutrient, which appears to be a 45ml vial. Sent Wyeast an email for clarification. Many shops are listing them as "1.5 fl oz", or 44ml. If they're 45ml vials, I need to scale my 40ml vials to them. If they're 50ml vials and the rest is for headspace, then I need to scale farther.

Looks like calculating percent solids by weight is really the best option at this point, as it ignores temperature and doesn't require cold crashing 48 hours for optimal compaction.

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Old 02-06-2013, 02:57 PM   #6
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Mr. Malty's slurry estimator has been way off in my experience. Especially the viability by date part
http://woodlandbrew.blogspot.com/201...ing-cells.html

Growth seems to be much more closely related to the amount of sugar than anything else in experiments I have run:
http://woodlandbrew.blogspot.com/201...ll-growth.html

And also in experiments that others have run:
http://braukaiser.com/blog/blog/2012...-yeast-growth/

Kai's work (above) was adopted by Brewers Friend:
http://www.brewersfriend.com/yeast-p...er-calculator/

I have recently re-ran my experiments with a different strain and have very similar results. It follows Balling's observation.

You probably do have about 300 billion cells.
3.8L * 9°P * 10 billion cells per liter per degree Plato = 342 billion.

Cell density can vary widely from one strain to the next. WLP004 is 100-200 million cells per ml, while WLP566 is 1000-1500 million cells per ml. The rule of thumb that seems to fit for most slurries is 1 billion cells per ml for yeast from a beer and 2 billion cells per ml for yeast from a starter.

You can really only know with a cell count
http://woodlandbrew.blogspot.com/201...viability.html

Which I would be happy do it for you:
http://woodlandbrew.blogspot.com/p/n...us-x-none.html

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Old 02-06-2013, 03:02 PM   #7
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That cell count procedure of yours just made my brain 'splode.

I'd love a cell count, but I don't want to intrude. It's OK for my hobbies to make me OCD and spend my time, but not for them to impose on others. Taste testing and keg floating not withstanding.

Since you think MrMalty and YeastCalc are off, I'd be willing to take a look into other calculation methods. Can you point me in the direction of a guide as to how you estimated 300b cells?

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Old 02-06-2013, 03:06 PM   #8
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Quote:
Originally Posted by thadius856 View Post
Trying to determine the ml capacity of the pictured vials. I think they're Wyeast Nutrient, which appears to be a 45ml vial.
They look like 50ml centrifuge tubes to me. Although, I think the numbers are in cells per milliliter, so the size doesn't really matter.
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Old 02-06-2013, 03:06 PM   #9
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Thanks for the mention Steve.

Yes, Mr Malty can be off quite a bit and Jamil and I seem to be getting into a fight over this (check out the beginning of Brew Strong from 12/24/12) I have the strong suspicion that Jamil did not use a series of stirred starters to come up with the growth curve for "stirred" in his calculator. I have no strong evidence for this, though, since he never published his experiments. You should press him on that.

My model as implemented in BF estimates a final cell count of about 650 B cells. but it can easily be 750 B.

Kai

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Old 02-06-2013, 03:08 PM   #10
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Quote:
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Thanks for the mention Steve.

Yes, Mr Malty can be off quite a bit and Jamil and I seem to be getting into a fight over this (check out the beginning of Brew Strong from 12/24/12) I have the strong suspicion that Jamil did not use a series of stirred starters to come up with the growth curve for "stirred" in his calculator. I have no strong evidence for this, though, since he never published his experiments. You should press him on that.

My model as implemented in BF estimates a final cell count of about 650 B cells. but it can easily be 750 B.

Kai
750b from ~80b vial and 380g of DME? That's quite the growth rate!
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