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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Yeast cell counting vs required amount
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Old 11-05-2013, 05:58 AM   #1
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Default Yeast cell counting vs required amount

So I count 400 cells in my hemocytometer using the simple method 5 squares of the 1 x 1 x .10 mm volume. The yeast was diluted in a 100 : 3 dilution (multiplier of 33). And I measure 175 ml of pure yeast volume - assuming 100% viability.

Doing this math give me 115 billion cells (400 x 5 x 33 x 175 x 10000).

I pitched this in a 19.5 plato wort of 11 gallons ale. Mr Malty's calculator says I need 608 billion cells.

I've got 5 times less than what is needed but the fermentation starts within 12 hours going strong. And this is what I have been seeing the last (3) batches where the amount of yeast cell that I have are a factor of 2 to 5 times less than what we are told they should be.

The wort was o2'd with pure oxygen for about 2 minutes at a low pressure (don't have a gas flow meter on the bottle). And then again about 3 hours after initially pitching.

When you look at Mr. Malty's calculator, it says 150 ml of yeast will be sufficient. But my initial calculation is well under the # of cells needed.

Any comments or suggestions from others would be welcomed as I'm scratching my head.


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Old 11-05-2013, 12:09 PM   #2
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I'm not sure what you are looking for. You can under pitch and the yeast will still ferment. A proper pitch will give you repeatable results - optimal flavors and a timely finish.


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Old 11-05-2013, 12:26 PM   #3
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Yeah, I think there is some skepticism among some home brewers about the pitching rates recommended on mrmalty and yeastcalc, but there is pretty widespread agreement with them too. It sounds link you want the skeptics to weigh in. I would just point out that you're mixing cases, insofar as you are counting actual yeast cells and then switching to talk about when fermentation starts and how vigorous you think it is (as if this is objectively measurable) as if those last things are dispositive. Even if we grant that your observations are valid, pitching rates are about things other than fermentation start time and vigor.
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Old 11-05-2013, 01:35 PM   #4
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My post was intent on asking the question of what I could be doing wrong. As we see so much in home brewing there isn't necessarily a right or wrong but preferred method.

I did make the leap on my pitching rate vs 'subjective' evaluation of air lock activity. My intent once again wasn't to look for a skeptic to reply but to ask the question to the folks who might be doing / asking these questions. If I am 5 times under the 'preferred' quantity where else could I be missing it?

When I dilute my 100 drops of water to 3 drops of yeast, I'm using a glass pipet with a very thin tip. The drop size seems to be similar between the (2). Just wondering is my multiplying factor might be off with respect to this?

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Old 11-05-2013, 02:12 PM   #5
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The factor 5 puzzles me. Shouldn't there also be an additional factor 4 or 5, depending on which and how many squares you count?
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Old 11-05-2013, 02:28 PM   #6
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The 5 multiplier is from the using the center grid of 25 squares. It is 1 mm x 1 mm. I count the corners (4) and the center (1) so I have to multiply by 5 to have the full area of (25).

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Old 11-05-2013, 03:25 PM   #7
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OK, I got ya. I see nothing wrong with your multipliers then. There could be somewhat variation when taking and dropping the yeast slurry, but nothing over say 5-10% from calculated, if that much.

The bigger question is how to assess the density of the yeast slurry. If Mr. Malty suggests 150ml should be appropriate and, while you've got even more at 175ml, at the same time you actually count way fewer cells than Mr. Malty predicted, something is off.

It is an interesting experiment, indeed.

We don't stand alone in finding Mr. Malty quite conservative in both calculating viability and estimating needed yeast cells for a good and active fermentation. That doesn't mean it's wrong, those could well be optimum amounts, scientifically proven and all. At the same time, it doesn't negate the fact that with less than half you can still blow off your airlock, or fail to taste stressed yeast syndrome. People have done qualitative side by side comparisons with pitching rates. I'm not sure what the outcomes were, and they'd still be highly subjective by any standard.

The 2 injections of pure O2 surely helped in the growth phase, and those may have contributed more than a larger starter would have. The yeast coming out of the starter is used to 1.040 while the yeast grown in your fermentor has adapted to your 1.081 wort.
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Old 11-06-2013, 02:10 AM   #8
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Just checked the intermediate gravity @1.054 using the hydrometer. Still actively burping away at a control fermentation chamber temperature of 68f. BTW, i used Denny's Favorite 50 1450. My mash efficiency was 80% and rested at 150 to 152 for 75 minutes.
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Old 11-06-2013, 03:34 AM   #9
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Quote:
Originally Posted by bbbrew
My post was intent on asking the question of what I could be doing wrong. As we see so much in home brewing there isn't necessarily a right or wrong but preferred method. I did make the leap on my pitching rate vs 'subjective' evaluation of air lock activity. My intent once again wasn't to look for a skeptic to reply but to ask the question to the folks who might be doing / asking these questions. If I am 5 times under the 'preferred' quantity where else could I be missing it? When I dilute my 100 drops of water to 3 drops of yeast, I'm using a glass pipet with a very thin tip. The drop size seems to be similar between the (2). Just wondering is my multiplying factor might be off with respect to this? BB
Why are your units in drops and not milliliters? Your dilution should be 1ml of yeast solution into 9ml water. Continue this dilution until you can accurately count cells. You counted 400 cells in 5 squares. I would recommend another dilution.

Make sure cells are evenly spread across the entire grid. Count the four corner and center squares. Then do the same for the other grid. If there is more than a 10% difference between the two grids; take another sample from your dilution and count again. It just takes practice.
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Old 11-06-2013, 07:17 PM   #10
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Indianaroller, I used drops just because I don't have a small graduated cylinder for 10 ml. My glass pipet has a long nose (for not knowing the technical term).

I decant off all the liquid (or as much as I can) from the starter and then just pull in yeast though that long nose of the pipet. It seem to be really consistent (creamy white) and since I only need one drop on the hemocytometer I didn't want to make a large amount. I thought this was a pretty good way of doing it.

I only count the center 1 mm x 1 mm square (25 small squares in all). And from that, I count the 4 corners and center. That's where my (5) multiplier comes in.
see here:
http://www.homebrewtalk.com/photo/he...rid-61305.html

I wish I knew how to insert a picture directly.


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