Counting Yeast Cells

The Wyeast Smack pack says 100 billion yeast cells... I suppose that is after it has swollen?

So if I use this and create a starter, with 3/4 wort and 3 cups of water to yield about an 800ml 1.040 starter. What kind of yeast growth can be expected over say 24 hours? Will the yeast double? More than double? How can you calculate or measure? Using a stir plate with the starter.

Thanks for any help!

It contains that before it swells. Smacking the pack does not grow cells, it just proofs them.

The Mr. Malty yeast calculator is really the best tool to figure this stuff out.

Labs usually measure cell count with a densitometer. Yeast viability is measured by methylene blue dye and counting under a microscope.

I was afraid you would say that ... years ago, maybe 30 I used those tools in the lab to count bacteria. I was just hoping there might be a better way to figure out how many cells you have. Mr. Malty is actually what got me thinking about this. My question really is: in 24 hours if you put 1 billion yeast cells in a 1.040 wort in a 1L flask on a stirplate, wouldn't the yeast have an exponential growth and number in the 10's of billions by then?

I ask because I don't really understand why I would pitch a starter over 1L ever. For a 1.070 wort and 5 gal Mr. M wants me to pitch about 1.5L or 250 billion cells. How can it be that 1 billion cells goes through a complete krausening on a stirplate over 24 hours and doesn't at least triple. I'm thinking it does way more than triple though. I guess I'm off to go research yeast growth rates.

I think you are on the right track, except for the fact that over that 24 hours, the yeast aren't multuplying. They go through their initial exponential growth phase, which is prolonged by a stirplate, then go into their respiration phases. A starter is as much about growing yeast as making sure they are very healthy. I'm not sure I completely understand growth rates, but I know Jamil has done extensive research on his own, and with Wyeast to determine these pitching rates.

Also, for large starters, you could stick it in the fridge for 24 hours, then decant off the liquid.

Netflyer said:

I was afraid you would say that ... years ago, maybe 30 I used those tools in the lab to count bacteria. I was just hoping there might be a better way to figure out how many cells you have. Mr. Malty is actually what got me thinking about this. My question really is: in 24 hours if you put 1 billion yeast cells in a 1.040 wort in a 1L flask on a stirplate, wouldn't the yeast have an exponential growth and number in the 10's of billions by then?

I ask because I don't really understand why I would pitch a starter over 1L ever. For a 1.070 wort and 5 gal Mr. M wants me to pitch about 1.5L or 250 billion cells. How can it be that 1 billion cells goes through a complete krausening on a stirplate over 24 hours and doesn't at least triple. I'm thinking it does way more than triple though. I guess I'm off to go research yeast growth rates.

Click to expand...

I've had questions about Mr. M myself. Almost sounds as if he is assuming there is a maximum density the yeast can reach?

Well, as far as max density, there are limiting factors. The amount of sugar will run out, the alcohol will cause the yeast to stop growing and multiplying, etc etc. I have been searching for good growth curves of yeast and it is hard to find a curve with just yeast in a wort. Most curves you find on the net are yeasts with other factors to test the way those factors limit the growth. It does seem though that the ratio of growth over 24 hours is about 2-4x as many cells as when the yeast were started. As for the Wyeast density, there may be 1 billion cells in that pack but the density is 6 million per ml. So another question arises about density per ml and the whole starter... When Mr. M has you make a 2 L starter that means 2L of wort, not 2L of yeast. I pitch my whole starter in the cooled wort instead of decanting liquid off the top and just attempting to pitch the yeast. My worts start to ferment in under 4 hours, and usually w/in 2 hours. Wyeast recommends 2 smack packs over 1.070 and 3 over 1.080 or the use of a starter...

I still think you can more than double your number of cells from a Wyeast smack pack using a stirplate in 24 hours...

Hermit said:

I've had questions about Mr. M myself. Almost sounds as if he is assuming there is a maximum density the yeast can reach?

Click to expand...

I'm assuming there is. If there weren't, then you could grow seventy quadruplebillion cells in 2 oz of wort. Obviously, thats not the case. Since you pretty much keep the gravity constant, bigger starter=more yeast. Wyeast also has a similar calculator which works a little differently. I'm almost positive its based pretty closely off of Jamil's.

Jamil comes around the forum every once and a while. Pretty sure his username is JamilZ. Think he has slacked off a little since the whole "I'm a Homebrewer" incident though.

You can also contact him at [email protected]. He may take a while, but he is pretty good at getting back to people.

Hermit said:

I've had questions about Mr. M myself. Almost sounds as if he is assuming there is a maximum density the yeast can reach?

Click to expand...

Jamil comes around the forum every once and a while. Pretty sure his username is JamilZ. Looks like he is still active. Forum search - member JamilZ. Maybe he'll make his way here and clear some things up. I'm just kind of spouting off info I've heard in podcasts etc.

You can also contact him at [email protected].

I hope you keep pushing for specifics on this subject. I for one, would really like to have more definitive information.

It all seems quite fuzzy to me an that's after asking some specific questions directly to Chris White (I'm sure he knows, and some how it's my fault but...)

What about stir plates? Add continuous aeration? How about some SPECIFICS ALREADY!! (read frustration here.)

Thanks

From the Wyeast website:

http://www.wyeastlab.com/hb_pitchrates.cfm

Check out the pitching rates they recommend... Keep in mind that:

Activator Package:

The Wyeast Activator (125 ml) smack-pack is designed to directly inoculate 5 gallons of standard ale wort (O.G. < 1.060, 65-72°F). When brewing high gravity beer (O.G. >1.060) or cold fermented lagers or ales (<65 °F)) additional yeast will be required. An Activator contains approximately 100 billion cells which will deliver slightly less than 6 million cells per milliliter to a 5 gallon batch of beer.

So this means their 1 billion cells pack delivers 6 million cells per ml to a 5 gallon batch... if you make a starter you can use their pitching calculator to see what size starter you would need for the gravity you want:

http://www.wyeastlab.com/hb_pitchrate.cfm

So basically if I need 12-13 million cells per ml for a 1.07 to 1.078ish wort, you can mess with the pitchrate calculator to see how large of a starter you need. I must say this corresponds very nicely to the amounts Mr. Malty suggests (as it should). Basically by deduction we can see that it is possible to at least double the amount of cells we start with because the Wyeast site calculator is based upon 24-36 hours of growth.

This is important too (also from the Wyeast site:
A low pitch rate can lead to:

• Excess levels of diacetyl
• Increase in higher/fusel alcohol formation
• Increase in ester formation
• Increase in volatile sulfur compounds
• High terminal gravities
• Stuck fermentations
• Increased risk of infection

High pitch rates can lead to:

• Very low ester production
• Very fast fermentations
• Thin or lacking body/mouthfeel
• Autolysis (Yeasty flavors due to lysing of cells)

So as much as a short lag phase is very desireable it seems that we don't want to over shoot that or we can end up in trouble too...

The only way to know is a with a hemocytometer. Used properly you can count live cells and not the dead ones. There are too many variables for something like mrmalty to be very accurate.

You could also check out http://maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices, but if you're like me, you may have to read it a few times.

-a.

You could use serial dilutions and plating to make a count

I'm going to paste a graphic in here that completely contradicts the information on Wyeast's site. I'm thinking the graphic is wrong and not the experts over at Wyeast. The trouble is I have seen this graphic referenced several times on the web in various articles. Now remember, from previous research and post Wyeast 250ml activators start out with 1 billion cells total (their claim) and that translates to 6 million / ml ... the amount per ml is important because cell density is more important to keep in mind than the total number of cells. Again, as I said in a previous post Wyeast's pitch rate shows that for a 1.073 wort I need about 12-13 million cells per ml, about double what is in an activator pack. If I grow up a 1.3ish liters of starter, in 24-36 hours I should have that number of cells. I have done other research that shows that within a 24 hour period the yeasts can 2.5-3.5 their number, this overshoots Wyeasts estimate in a pure sense but Wyeast is taking into account other limiting factors such as reduction of fermentables, reduction of O2, presence of alcohol, volume of wort, and others I'm not thinking of. Anyhow, so this graphic is what I find in several places on the net:



What is wrong with this picture? I'm thinking that the legend on the graphic should be yeast counts in millions/volume starter and not per/ml ... Even that analysis seems wrong... just don't know...
If my stirred starter yielded 250 million cells/ml after 24/36 hours according to Wyeast we would be VASTLY overpitching. And, they claim their activators will go from 6 million/ml to 12 million/ml in 24-36 hours (1 Liter of starter)... not from 6 million to 250 million.

The point is you need the correct amount of cells to make a great beer, too many cells and you might take the body right out of it, if it doesn't have much body that might be exactly what you want...

I will always make a starter, Wyeast recommends using more than one activator package if your wort's OG is over 1.060 or making a starter, if over 1.080 they recommend 3 packs or a large starter

http://www.wyeastlab.com/com-yeast-harvest.cfm

This helps me understand yeast counts when I get confused. Scroll down until you see the yeast slurry percentages in test tubes. They estimate that 1 ml of pure yeast is around 2.4 billion cells. From there you can estimate how much you have by using their tip.

As for the graphic above, it is a bit confusing but that article as a whole is very good. Notice there is an error bar for the stirred bar too. I've found by estimating that the limit is 180 million/ml in a starter solution at 1.039 sg. I think Mr Malty's numbers are around 150 million/ml of starter solution. I trust Jamil's calculator has is numbers have been verified by wyeast and that my rough estimates were close enough to his.

If you want to take this further, I suggest getting a micropipet, some inoculation plates and some test tubes and start doing serial dilutions, plating and colony counts. That is a good enough way to show how many living cells are in the original solution.

Netflyer said:

I was afraid you would say that ... years ago, maybe 30 I used those tools in the lab to count bacteria. I was just hoping there might be a better way to figure out how many cells you have. Mr. Malty is actually what got me thinking about this. My question really is: in 24 hours if you put 1 billion yeast cells in a 1.040 wort in a 1L flask on a stirplate, wouldn't the yeast have an exponential growth and number in the 10's of billions by then?

I ask because I don't really understand why I would pitch a starter over 1L ever. For a 1.070 wort and 5 gal Mr. M wants me to pitch about 1.5L or 250 billion cells. How can it be that 1 billion cells goes through a complete krausening on a stirplate over 24 hours and doesn't at least triple. I'm thinking it does way more than triple though. I guess I'm off to go research yeast growth rates.

Click to expand...

A constantly aerated starter (think stirplate) produces 10M-15M cells/(mL*P) by the time all the resources (sugars) are depleted. Since 1.040 is about 10 degrees Plato, you'll produce about 10M * 800 * 10 = 80 billion.

rocketman768 said:

A constantly aerated starter (think stirplate) produces 10M-15M cells/(mL*P) by the time all the resources (sugars) are depleted. Since 1.040 is about 10 degrees Plato, you'll produce about 10M * 800 * 10 = 80 billion.

Click to expand...

A 1L starter?

Netflyer said:

A 1L starter?

Click to expand...

10M cells/(mL*P) * 10P * 1000 mL = 100 billion cells.

Thanks man

A constantly aerated starter (think stirplate) produces 10M-15M cells/(mL*P) by the time all the resources (sugars) are depleted. Since 1.040 is about 10 degrees Plato, you'll produce about 10M * 800 * 10 = 80 billion.

Click to expand...

Rocketman, I'm having these number square with Mr. Malty's numbers.
What is the '800' number here?
Also, do you remember the source of the 10-15mm cells/ml?
I'm trying to fashion a spreadsheet for future reference and appreciate your help.

Edcculus said:

Jamil comes around the forum every once and a while. Pretty sure his username is JamilZ. Looks like he is still active. Forum search - member JamilZ. Maybe he'll make his way here and clear some things up. I'm just kind of spouting off info I've heard in podcasts etc.

You can also contact him at [email protected].

Click to expand...

He's also writing a book with Chris White (White Labs) on yeast, due out towards the year's end. I think I read the first draft is done...

If you have any suggestions for the book, he's looking:
http://www.thebrewingnetwork.com/forum/viewtopic.php?f=19&t=18526

nealperkins said:

Rocketman, I'm having these number square with Mr. Malty's numbers.
What is the '800' number here?
Also, do you remember the source of the 10-15mm cells/ml?
I'm trying to fashion a spreadsheet for future reference and appreciate your help.

Click to expand...

It was 800 mL. I'm not sure what the original source of 10-15M cells/(mL*P) was. The calculator looks pretty spot on to me. Set the aeration method to stir plate, OG to 1.084, and volume to 5.25 gal. It tells you you need 300G cells. It tells you that you need 2 vials of yeast (which is 200G cells) and 1 L of starter which is 100G more cells if you assume 10M cells/(mL*P), and the starter gravity is 10 Plato.

Got it, thanks.

Next question: If I have a 3L starter, begun with 1 vial of yeast, finish it, pour off the 'beer', and step it up with another 3L of wort; what would that produce?

The more general question has to do with the starting yeast count.

Thanks

nealperkins said:

Got it, thanks.

Next question: If I have a 3L starter, begun with 1 vial of yeast, finish it, pour off the 'beer', and step it up with another 3L of wort; what would that produce?

The more general question has to do with the starting yeast count.

Thanks

Click to expand...

After you decant, there's no telling how much yeast you poured off since each yeast has different flocculation levels. However, if you assume that somehow you didn't pour off any yeast, the effect (as far as yeast count) would be the same as if you had made a 6L starter from 1 vial.

Thanks.
I should have mentioned that I let the starter drop clear prior to pouring.

A couple observations:

1. If you're making 10 or more gallons of lager, that's a lot of starter. Maybe there's a place for dry yeast..or

2. Pitching on top of a 5 gallon batch is starting to make perfect sense!