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View Poll Results: Would you be interested in having a cell count done on your slurry?
I have a slurry right now that I would like tested 3 42.86%
There may come a time that this would be interesting. 4 57.14%
Cell Counts? Itís not going to make better beer. 0 0%
Voters: 7. You may not vote on this poll

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Old 12-07-2012, 01:19 AM   #1
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Default Lab testing for slurry cell counts and viability

Is there interest in knowing the cell count of slurries?

It’s something that I find particularly useful especially since discovering how wide the viable cell count can range. A variation of a factor of ten is more common than many brewers would be comfortable with.

If a sample of yeast is mailed to me in a White Labs vial, the testing can be conducted and a report can be written within 24 hours of receiving the sample.

Knowing the cell count of a slurry can save you time and money. A vial of yeast is about $8, and the DME needed for a 2 litter starter is about $3. That’s about one third the cost of a batch of beer.

The tests would include the following:
Viability – The percentage of viable cells of the total cells.
Cell Density – The number of viable cells per milliter and per gram.
Stress Level – The ratio of budding cells to conjoined cells. Budding cells indicate healthy yeast growth while conjoined cells are a sign of yeast stress.
Bacteria Level – percentage of visible bacteria for each yeast cell. Note that some bacteria are smaller than can be seen with a microscope. This is only an estimation of bacteria. It is possible for there to be bacteriological contamination even if zero bacteria are seen.
Alcohol Tolerance – The alcohol level that reduces the viability by half.

In addition I could perform fermentation tests:
Attenuation Rate – The percentage reduction of gravity per day. This is typically tested in a 1.035 specific gravity wort made with Briess Light DME and fermented at ambient air temperature. To better model how you may be using this yeast testing can be done a gravity of up to 1.100.
Total Apparent Attenuation – Percentage of sugar converted to alcohol during fermentation.
Flocculation – percentage of yeast cells that fall out of suspension per day during fermentation.

What do you think, Do you have interest in having a slurry tested?

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Old 12-14-2012, 07:24 PM   #2
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If you want more details check here:
http://woodlandbrew.blogspot.com/p/n...us-x-none.html

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Old 12-15-2012, 09:58 AM   #3
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Yes I do for sure.

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Old 12-15-2012, 12:40 PM   #4
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I think it's a nice idea but how can you gaurantee the results of the sample are the same as when the sample was fresh? The time in transit will certainly effect viability of the slurry.

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Old 12-15-2012, 01:43 PM   #5
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You're right, it's not going to be the same, but it will be close. Fresh slurry viability can vary from the high nineties all the way down to 10% in my experience. Some slurries I have harvested that have been sitting at ambient conditions for over a week after fermentation completed and have been over 90% viable. So I don't see that it would drop much during transportation, but this is something that I am looking into.

Slurry density also varies widely. On slurries I have counted I have seen from 200 billion cells per liter all the way to almost 2 trillion cells per liter on a fairly regular basis.

Between these two factors estimates without a microscope could be off by a factor of 100.

The counts would likely be within 10% of the slurry that it was taken from.

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Old 12-15-2012, 08:52 PM   #6
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I hate to be that guy, but how much would it cost?

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Old 12-15-2012, 10:15 PM   #7
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Free for cell count based testing, and $5.00 for fermentation based tests.

For details go here:
http://woodlandbrew.blogspot.com/p/n...us-x-none.html

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Old 12-16-2012, 05:10 PM   #8
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Wow!! That sounds awesome. I regularly grow up my own yeast on a stir plate and have wondered about cell counts as well as bacterial contamination.

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Old 12-19-2012, 12:37 PM   #9
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Quote:
Originally Posted by Phunhog View Post
Wow!! That sounds awesome. I regularly grow up my own yeast on a stir plate and have wondered about cell counts as well as bacterial contamination.
I'd be happy to test it. When you are ready to have it tested send me a PM and we can work out the details.
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