I'm still trying to figure out these yeast starter basics

[NYShooterGuy]

I've been making yeast starters for over a year now (approx. 20-30 starters made in that time). I'll try to give all the info to help everyone understand my problems.

I use:

light DME
2L erlenmeyer flask
Stir plate (and magnet of course)
Approx 1/4 tsp yeast nutrient

I uttize:

http://www.brewunited.com/yeast_calculator.php

to calculate what I need to make the correct amount of yeast for my brew.

I store my yeast in sterile mason jars and sterile water (pre-boiled, cooled, and then the lids sanitized prior to opening the jars and adding the yeast to store.)

My biggest problem is estimating how much yeast I have in the jar prior to making the starter. If the yeast is at the 50ml line in the jar, I was told that I should have approx 1.2 - 1.5 billion cells per ml (60 - 75 billion cells)

I don't know if this translates to all the yeast varieties or if it just for most. I'm just confused about how many I should be able to guess I have.

As for the other problems, I just made a starter Saturday with yeast leveled in between the 0 and 50ml line (estimated 30ml) and added it to a 2L starter with 201grams DME.

I let it spin for 19 hours and noticed the highly focculant Wyeast London ESB yeast clump and swirl in a cottage cheese consistency before I cold crashed it.

I decanter the beer, added my harvest to a sterile jar and after it settled ended with approx 110-120ml of yeast.

The software I used estimated almost twice that amount so I was wrong somewhere.

The yeast was approx manufactured 3.5 months prior and I calculated that factor into the software, and I stopped the stir plate after only 19 hours because of the clumpy nature of the yeast in the flask.

I'm guessing either the yeast was not as hearty as expected, the time on the stir plate was not long enough, or the software was in error.

Any help with helping me understand this or solutions is greatly appreciated.

Thanks gang!

 

[TheMadKing]

2 billion cells/mL is a good average. Your starting cell count doesn't matter as much as your starter volume. Yeast will essentially multiply to fill a food supply, so whether you start with 30 billion cells or 50 billion cells, you're going to end up with pretty close to the same finished number of cells.

Your second problem, I think you had a math error in your prediction. I just calculated it out and got 159mL which is fairly close to your 120mL measurement.

My math:

30mL x 2billion cells/mL = 60 billion cells
3 months old gives a viability of 62% (per brewunited) so you actually pitched about 37 billion cells into your starter
201 g of DME in 2L = 1.037 SG
2L @ 1.037 with 37billion cells pitched on a stir-plate should result in 319 billion cells.
319 billion cells / 2 billion cells /mL = 159.5 mL of slurry.

This volume measurement method is very inaccurate and is dependent on a lot of factors (how long has it been sitting cold, yeast cell size, trub in your wort, etc).

Don't worry about getting the cell count correctly down to the nearest 1 billion. If you are within 50 billion cells of your desired pitch rate, I think you're doing fine. There are too many assumptions in yeast cell calculations to realistically have any certainty of accuracy.

 

[sky4meplease]

I told you 1.2-1.5 billion cells per milliliter. That is what I find in my cell counts on average.
Something to consider is we are typically working with many different strains of yeast with different characteristics and in an environment where we don't have a tremendous amount of control.
I remember when I started counting yeast my first strain was labeled "very flocculant". I pulled my hair out trying to break up flocs and get consistent counts and almost quit before I started.
Today I did a count and had 1.77 billion cells per milliliter. I have never seen 2.0 or higher.
Point is it's not an exact science at the level we are doing it.
Without a lab the best you can do is work with healthy yeast so you can assume high levels of viability, measure your slurry volume as accurately as possible and multiply that by a conservative per ml number to estimate your pitch rate.
If you do that and come up short then make another starter and build up some more yeast or pitch it as is. Some of this can depend on the beer you are brewing. Some beers are fine pitched a little low while I will put a brew day on hold to build up numbers for others (i.e. Big beers/lagers).
As far as the online calculators are concerned, I typically use the lowest model if I use one at all because I almost always find I come up short. Maybe I suck at making starters or maybe the people who built the models are really good at it.

 

[NYShooterGuy]

I have a microscope and yeast cell counting software on my wish list to more accurately know how many cells I have. Of course, for now, it's guess work.

As far as this last starter, all I know for certain is I started with about 30 ml of bright white yeast cells approx 3.5 months old, and in 19 hours on 201 grams of DME in 2L of water, it multiplied to about 120 ml of bright white yeast.

I then made my second starter with 1.8L water and 201 grams DME and pitched the 120 ml of yeast and 80 ml of water into the starter.

Based on the software, it hope to get at least 420 billion cells.

I always try to overbuild so I can take 100 billion away from the starter for the next batch's starter and pitch the cells needed for the current brew.

Based on the information that I've been getting in the past few days, I've been under pitching quite a few brews. The beers have been "okay", but I wonder if my errors with under pitching are why they're not "Great!"

I think I read somewhere that over pitching can be detrimental to the taste of the beer as well. If that's the case, then I would really like to get on target with my yeast counts. I guess the only way is to do many batches and only change 1 thing at a time...this could take a while.

 

[logdrum]

I have a microscope and yeast cell counting software on my wish list to more accurately know how many cells I have. Of course, for now, it's guess work.

As far as this last starter, all I know for certain is I started with about 30 ml of bright white yeast cells approx 3.5 months old, and in 19 hours on 201 grams of DME in 2L of water, it multiplied to about 120 ml of bright white yeast.

I then made my second starter with 1.8L water and 201 grams DME and pitched the 120 ml of yeast and 80 ml of water into the starter.

Based on the software, it hope to get at least 420 billion cells.

I always try to overbuild so I can take 100 billion away from the starter for the next batch's starter and pitch the cells needed for the current brew.

Based on the information that I've been getting in the past few days, I've been under pitching quite a few brews. The beers have been "okay", but I wonder if my errors with under pitching are why they're not "Great!"

I think I read somewhere that over pitching can be detrimental to the taste of the beer as well. If that's the case, then I would really like to get on target with my yeast counts. I guess the only way is to do many batches and only change 1 thing at a time...this could take a while.

How are you fitting all of this into a 2L flask? Also are you adding the cover water? Best practice is to store the yeast under the spent wort & decant before pitching

 

[sky4meplease]

Let us know how it works out.
If your starting with something that has been stored a while you can start with a slightly smaller lower gravity to wake the yeast up before you put them to work.

 

[NYShooterGuy]

How are you fitting all of this into a 2L flask? Also are you adding the cover water? Best practice is to store the yeast under the spent wort & decant before pitching

Sorry for the confusion, I didn't really go into detail on that.

I collect the yeast, wort and sterile water in 8 oz mason jars (slightly more than 200ml) and try to decant as much wort as possible to fill with sterile water. So if I know I'm making a 2L starter I make a 1800ml stater with 201 grams of DME, then, after it cools to the same temperature as the mason jar of yeast and water/wort mix, I add it to the flask to make a total of 2000ml.

It adds a little spent wort (I never do a gravity reading so I really don't know how diluted it is, but I try to make it only yeast and sterile water).

My very first yeast starter was an overflowing mess that I had to scramble to figure out a solution. The flask couldn't hold the 2L of water and DME I made and realized that the 32 oz jar of yeast would overflow the flask, so I had to store some and then retry again, and it was an awful beer after I worked it all out. It had the aftertaste of apples in an Imperial IPA that I pitched the overflow 3 days later into the fermenter after I grossly under pitched initially on brew day.

So now I have to remember the volume of the yeast and water/wort mixture prior to adding the water to the DME in the flask.

Egh. I know it's not the best way, but I'm still asking questions and trying to learn.

 

[NYShooterGuy]

Let us know how it works out.
If your starting with something that has been stored a while you can start with a slightly smaller lower gravity to wake the yeast up before you put them to work.

I have about 4 or 5 jars of about 1ml of stored yeast that I haven't touched in over 12 months. I'm guessing these are all almost entirely dead. I figure if I had some spare time on my hands when not chasing my 4 kids all under the age of 5 around, I could make VERY small starters (20ml) to see if there is any activity and then try to make a larger population, but I'm probably better off spending $7 for a healthy 80+ billion cells from the lab. I like to experiment so I might just see if they have any life in them to play around before I plan a brew day and end up in trouble.

 

[sky4meplease]

You might as well order yourself a 3&5 liter flask.
I haven't pulled the trigger on the 5 liter flask because I wouldn't get it on my stir plate where it is stored to keep it warm.
Once I max out in my 3 liter flask I move to 2 or 5 gallon buckets for starters and inject O2 during propagation.
I think you will find the limitation of your 2 liter flask when you reach cell counts that saturate your 1500ml starters. It will limit growth and you will need to step up in container size.

 

[catdaddy66]

You mention you have been making starters for a year or more. How has your beer turned out?

If you are pleased with the final results then I wouldn't sweat the minutia, personally. If not, more experiments may be necessary.

To me the end justifies the means (as far as yeast goes)!

 

[NYShooterGuy]

You might as well order yourself a 3&5 liter flask.
I haven't pulled the trigger on the 5 liter flask because I wouldn't get it on my stir plate where it is stored to keep it warm.
Once I max out in my 3 liter flask I move to 2 or 5 gallon buckets for starters and inject O2 during propagation.
I think you will find the limitation of your 2 liter flask when you reach cell counts that saturate your 1500ml starters. It will limit growth and you will need to step up in container size.

I was wondering if taking new cells from the finished starter to store (100 billion or so) and then making 2nd and 3rd steps with the lower cell count due to the removed cells would be effective?

 

[NYShooterGuy]

Update:

The batch I pitched 120 ml of yeast into the 1.080 OG porter was sampled today. Refractometer read 11 brix. (Calculated to 1.023 SG). According to wyeast website the strain (London ESB) the yeast fully attenuated.

Sample tasted great. Not sure what the factors were.

This was the first time I left the fermenter in the Kezzer at 64°F for 7 days, also from my understanding, porters stouts and IPA's are forgiving with off flavors from fermentation.

 

[sky4meplease]

What was your target pitch rate for that beer?
I think it's funny you probably pitched twice as much yeast as most home brewers would have and yet some would consider that under pitched by half.

 

[NYShooterGuy]

What was your target pitch rate for that beer?
I think it's funny you probably pitched twice as much yeast as most home brewers would have and yet some would consider that under pitched by half.

According to http://www.brewunited.com/yeast_calculator.php I needed 302 billion cells. I pitched 120 ml of the London ESB yeast that was stored from a previous starter approximately 3.5 months prior.

 

[specharka]

IME yeast cell counts matter very, very little. Whether it's 50 mL or 250 mL of slurry, the bigger factor in reaching terminal gravity is yeast vitality. If yeast is well oxygenated, has access to ample food and nutrient sources, and has been actively fermenting, there is no reason that it should not reach terminal gravity. I have tried under pitching several times to encourage ester formation and still reached terminal gravity due to the performance of the vitality starter.

 

[NYShooterGuy]

IME yeast cell counts matter very, very little. Whether it's 50 mL or 250 mL of slurry, the bigger factor in reaching terminal gravity is yeast vitality. If yeast is well oxygenated, has access to ample food and nutrient sources, and has been actively fermenting, there is no reason that it should not reach terminal gravity. I have tried under pitching several times to encourage ester formation and still reached terminal gravity due to the performance of the vitality starter.

I only had a few beers that had problems fully fermenting. One was a brew early in my homebrewing career.

I didn't realize the yeast strain I was using had a lower alcohol tolerance and ended up using a champagne yeast to help it along (unsuccessfully). It carbonated in the bottles after about 8 months.

Another was White Labs Brettanomyces Bruxellensis Trois that I wanted to grossly underpitch (half the vial than for a 3.5 gallon batch of 1.058 OG) because I wanted the flavors of the stressed yeast. It was a good tasting beer, but didn't have the "liquid Skittles" flavor I was hoping.

And yet another 2 beers were more resent (both fermented with Wyeast London ESB) and slowed fermenting in the bucket. Even after 4 to 6 weeks in the bucket they hadn't finished fully fermented and I never checked the estimated FG before bottling. Those resulted in bottle bombs and I began a habit of sanitizing a brew spoon to agitate the yeast from the bottom to rouse the yeast and hopefully finish up when using this strain.

 

[sky4meplease]

IME yeast cell counts matter very, very little. Whether it's 50 mL or 250 mL of slurry, the bigger factor in reaching terminal gravity is yeast vitality. If yeast is well oxygenated, has access to ample food and nutrient sources, and has been actively fermenting, there is no reason that it should not reach terminal gravity. I have tried under pitching several times to encourage ester formation and still reached terminal gravity due to the performance of the vitality starter.

Check out this:
http://www.probrewer.com/library/archives/quality-control-in-the-brewery/

Dr. Michael J. Lewis wrote in that article:

Generally, brewers are well aware of the need for specification and consistency (quality) in the brewhouse operations. That might be said with less confidence in cellar management — in wort aeration, fermentation temperature, and so on — and there is one glaring shortcoming in many breweries that is worth mentioning: control of the yeast pitching rate.

Michael J. Lewis, Ph.D., is professor emeritus of brewing science at the University of California, Davis, and the academic director and lead instructor of UC Davis Extension’s Professional Brewing Programs. Lewis has been honored with the Master Brewers Association of the Americas’ Award of Merit and the Brewers Association’s Recognition Award. He is an elected fellow of the Institute of Brewing & Distilling. He is also a recipient of the UC Davis Distinguished Teaching Award.

If it's good enough for him it's good enough for me.

 

[NYShooterGuy]

I guess what I get out of that article is that consistency is important of you want a repeated product. Once you change a variable, the product can be different.

So if you're happy with a beer that is underpitched, do the same process. If not, change a variable.

I have yet to brew (out of 52 batches) the same beer the same way. My first beers were horrible, I changed variables (fermentation temps, equiptment, yeast propagation, etc.) and found them ,for the most part) improving.

On the ones that still didn't taste great, I have to change more variables. On the ones that tasted great, I'll do the same process and expect the same result when I finally get around to making those great beers again.

For now I'm still trying many different recipes and varieties and haven't found too many that I wanted to have a 2nd crack at just yet.

 

[sky4meplease]

Something I have gone to doing is pulling a 10ml sample from my flask when I believe the starter is done or almost done.
I put that sample into a 10ml graduated cylinder (I think I got the cylinder and 10ml pipette from my LHBS). The cylinder goes into the fridge for 24 hours to cold crash. Meanwhile the starter can continue to run if your going to split it or in the fridge with the cylinder if your pitching the whole thing or planning to step it up again.
So say you have 2000ml starter and your cylinder settles to 1ml of slurry then you should have 200ml of slurry in your flask when it settles. If you take your 200ml multiply by 1.5 you should have roughly 300 billion cells.
This is a little crude if your not physically counting the cells under a microscope but it will get you in the ballpark.
Another example 1500ml starter, 10ml sample settles to .08ml slurry = 1500 x .08 = 120ml slurry x 1.5 = 180 billion cells.

View attachment ImageUploadedByHome Brew1481915687.343604.jpg

 

[NYShooterGuy]

Something I have gone to doing is pulling a 10ml sample from my flask when I believe the starter is done or almost done.

Sounds like you have a good routine.

I'm much lazier, or just stubborn to my routine. I put the flask in the fridge to cold crash, decant the beer into sanitized mason jars, and and pre-boiled and cooled water into the flask to know I would need a precalculated fraction of the total in the mason jar for the wort I had made in brew day. Then the rest gets stored into yet another sanitized mason jar (usually much smaller jar) and stored for the next starter.

It's more steps but, again, I'm probably just stubborn to my routine.

 

[CA_Mouse]

I think I read somewhere that over pitching can be detrimental to the taste of the beer as well. If that's the case, then I would really like to get on target with my yeast counts. I guess the only way is to do many batches and only change 1 thing at a time...this could take a while.

It is very difficult for us as homebrewers to severely overpitch our beers. unless you are doing one gallon batches and pitching enough yeast to ferment out a one barrel batch.

I have played with different pitching rates, specifically with Belgian yeast strains, and, other than the expected differences in esters, they have all been very good beers. Yeast vitality is the most important thing, followed by proper temperature control.

 

[sky4meplease]

Seems like everyone agrees the yeast have to be alive.

 

[NYShooterGuy]

Yeast vitality is the most important thing, followed by proper temperature control.

Agreed. I think I'll err on the side of caution for my subsequent batches from now on. I'll assume 1B cells per ml of slurry, always make starters to assure my yeast is alive, and (hopefully) have many great beers to enjoy in the future.

So many batches have I made that just ended up carbonated liquid that I was disappointed with.

After I acquired a kezzer, I was able to control fermentation temps much better, and at least the beers got slightly better. Now I will address my pitch rate and better lock in a standard.

 

[sky4meplease]

Agreed. I think I'll err on the side of caution for my subsequent batches from now on. I'll assume 1B cells per ml of slurry

I think that is a good plan given your strategy for harvesting for future brews. It may have you slightly over pitching but allows for some cell death due to long storage. Slightly over pitching is better than under pitching.
Look into water chemistry as well. In my opinion that took my brewing to another level. Using the right water for the beer you are brewing puts your PH in line which is good for the yeast and gives you control over chloride to sulfate ratio (malt to bitterness balance).
Good luck. Let us know how things progress.

 

[NYShooterGuy]

Look into water chemistry as well. In my opinion that took my brewing to another level. Using the right water for the beer you are brewing puts your PH in line which is good for the yeast and gives you control over chloride to sulfate ratio (malt to bitterness balance).
Good luck. Let us know how things progress.

That could be why the darker beers turn out best for me especially when all grain BIAB. I never have test PH before, and I just assumed it would be expensive? If you have any resources on equipment / products / links on adjusting PH for recipes I'd really be interested in learning about that to make my beer better.

 

[sky4meplease]

I don't want to hack your thread here so feel free to pm me and I will see what I can do to get you started.

 

[CA_Mouse]

After I acquired a kezzer, I was able to control fermentation temps much better, and at least the beers got slightly better. Now I will address my pitch rate and better lock in a standard.

Some of my best beers have been fermented starting at the lowest range for that particular yeast and allowing it to run free up to close to it's maximum temperature. So for Cal Ale I would start it at about 62*F and let it free rise to about 66*F.

That could be why the darker beers turn out best for me especially when all grain BIAB. I never have test PH before, and I just assumed it would be expensive? If you have any resources on equipment / products / links on adjusting PH for recipes I'd really be interested in learning about that to make my beer better.

Your darker malts will add a bit more of a buffer to your wort. All light beers may need help depending on your water chemistry. You should be able to get a Water Report from your city or Municipal Water District. Use your brewing software if you have some or use Bru'n Water.

 

[NYShooterGuy]

Not exactly sure where I went wrong with my last step since my previous posts. I had 150 milliliters of yeast and ended up with just over 200 milliliters of yeast. The starter I used had 1800 milliliters of water, 201 grams of DME, and the 50 milliliters of sterile water, + 150 milliliters of yeast in the Mason jar. 1800, plus 150, plus 50 equals 2 liters.

 

[sky4meplease]

This is where you are realizing the limitations of your equipment.
You put 225 billion cells into 1,800 milliliters of wort.
That is 125 million cells per milliliter inoculation rate which is pretty high or saturated.
At the stage you were at you would have been better off separating 150 billion cells (1,333 milliliters) of the starter, cold crash and decant the remaining 667 milliliters (75 billion cells) and adding 1,800ml +\- fresh wort to that.
That would keep your inoculation rate to about 40 million cells per milliliter. Much better growth at that rate.
Basically you will be leaving enough in your flask to maintain an optimal inoculation rate and harvesting the rest.
Otherwise you are just wasting precious wort.

 

[sky4meplease]

And those aren't hard numbers.
You can tweak them to work with your harvesting container sizes but try to keep your inoculation rates to 40-60 million cells per milliliter. I think you will get the best bang for your buck there.

 

[AndrewduToit]

Tried to calculate how big my yeast starter should be with for a 60L batch. According to Brewers Friend on the internet, I need a 10 Litre starter. Not even bothered about the cell count. Just want my beer to ferment. It seems the gravity reading before and after you adding the yeast is more important.

 

[sky4meplease]

Tried to calculate how big my yeast starter should be with for a 60L batch. According to Brewers Friend on the internet, I need a 10 Litre starter. Not even bothered about the cell count. Just want my beer to ferment. It seems the gravity reading before and after you adding the yeast is more important.

Just buy extra packs of yeast if you don't want to make a starter.
Tell your LHBS you are doing a 15 gallon batch and your OG and they will tell you how much you need.

 

[allanmorgan]

Not sure if this is relevant to you guys or not, but Neva Parker from White Labs had this to say about starters:

there is a general consensus among homebrewers that a starter is always necessary with any yeast. While I don’t necessarily disagree, what I always try to guide people towards is the right way to make a starter, or at least understanding that a starter in and of itself is not growing a whole bunch of new yeast. I think that’s just a misconception that people have about starters in general. You know, “I’m just going to take a package of yeast that I buy, throw it into a one- or two-liter starter, and I’m just going to double or triple or quadruple the amount of yeast that I have,” but that’s just not true. There’s not enough food and nutrients there to have that happen.

Essentially, a starter is beneficial in that it wakes the yeast up, it gets their metabolism going so that by the time you add it, your fermentation is going to be kick started because the yeast is already active. I think that’s one thing to always remember. It’s not absolutely necessary to have a starter every time unless you’re brewing high gravity beers. If you want to make a starter, just keep in mind that you’re not getting a ton of yeast growth, it’s mostly just an activation process

The whole article is on HBT's home page.

 

[sky4meplease]

Not sure if this is relevant to your guys or not, but Neva Parker from White Labs had this to say about starters:

there is a general consensus among homebrewers that a starter is always necessary with any yeast. While I don’t necessarily disagree, what I always try to guide people towards is the right way to make a starter, or at least understanding that a starter in and of itself is not growing a whole bunch of new yeast. I think that’s just a misconception that people have about starters in general. You know, “I’m just going to take a package of yeast that I buy, throw it into a one- or two-liter starter, and I’m just going to double or triple or quadruple the amount of yeast that I have,” but that’s just not true. There’s not enough food and nutrients there to have that happen.

Essentially, a starter is beneficial in that it wakes the yeast up, it gets their metabolism going so that by the time you add it, your fermentation is going to be kick started because the yeast is already active. I think that’s one thing to always remember. It’s not absolutely necessary to have a starter every time unless you’re brewing high gravity beers. If you want to make a starter, just keep in mind that you’re not getting a ton of yeast growth, it’s mostly just an activation process

The whole article is on HBT's home page.

That is true at certain inoculation rates. At others you are certainly growing yeast.
This is where this thread has gone recently if you read back. The OP is having trouble growing yeast in any appreciable numbers because he has maxed out his equipment.
Keeping the inoculation rate low but not too low and you will grow yeast.
I recently maxed out my 3L flask and did a 2 gallon starter to get the 600 billion cells I needed for a big Ale.
If you have 200 billion cells and throw 1500 ml wort at it (133.33 million cell per milliliter) you won't see much growth but throw 5,000 milliliters at it and see what happens.

 

[allanmorgan]

That is true at certain inoculation rates. At others you are certainly growing yeast.

I figured that might be the case, but wanted to throw it out there anyway. Thanks sky4meplease!

 

[peterlonz]

An awful lot of concern over something which in practice is not very important.
You do need healthy yeast in sufficient quantity.
7 sometimes 11 grams of quality dried yeast is sufficient for a 23 litre brew & it can be pitched directly.
The difference between "direct dry pitched" & "starter pitched" is mainly one of cost not final taste, at least that is my experience.
BTW I don't believe over pitching or pitching a trub+yeast mix will create problems either.

 

[ScrewyBrewer]

This is where you are realizing the limitations of your equipment.
You put 225 billion cells into 1,800 milliliters of wort.
That is 125 million cells per milliliter inoculation rate which is pretty high or saturated.
At the stage you were at you would have been better off separating 150 billion cells (1,333 milliliters) of the starter, cold crash and decant the remaining 667 milliliters (75 billion cells) and adding 1,800ml +\- fresh wort to that.
That would keep your inoculation rate to about 40 million cells per milliliter. Much better growth at that rate.
Basically you will be leaving enough in your flask to maintain an optimal inoculation rate and harvesting the rest.
Otherwise you are just wasting precious wort.

From the chart in the book Yeast, on pg.143, it seems to show that 100 billion cells in a 2 liter 1.035 wort will yield around 200 billion cells. Doubling the yeast count and the starter wort volume to 4 liters and 200 billion cells will yield about 400 billion cells.

"2L @ 1.037 with 37billion cells pitched on a stir-plate should result in 319 billion cells."

 

[sky4meplease]

From the chart in the book Yeast, on pg.143, it seems to show that 100 billion cells in a 2 liter 1.035 wort will yield around 200 billion cells. Doubling the yeast count and the starter wort volume to 4 liters and 200 billion cells will yield about 400 billion cells.

That is fairly consistent with what I have experienced in my lab.
In both cases the inoculation rate is 50 million cells per milliliter. Plenty of food to go around.
I like to stay between 30-50 million cells per milliliter because I typically wait until the later stages before I start counting so as to make sure there is plenty of sugar to promote growth. At this point the yeast are plenty viable. I am making yeast.

 

[sky4meplease]

"2L @ 1.037 with 37billion cells pitched on a stir-plate should result in 319 billion cells."

I have never seen growth like that. It sure would be nice though.

 

[sky4meplease]

Check out this:
http://www.probrewer.com/library/archives/quality-control-in-the-brewery/

Dr. Michael J. Lewis wrote in that article:

Generally, brewers are well aware of the need for specification and consistency (quality) in the brewhouse operations. That might be said with less confidence in cellar management — in wort aeration, fermentation temperature, and so on — and there is one glaring shortcoming in many breweries that is worth mentioning: control of the yeast pitching rate.

Michael J. Lewis, Ph.D., is professor emeritus of brewing science at the University of California, Davis, and the academic director and lead instructor of UC Davis Extension’s Professional Brewing Programs. Lewis has been honored with the Master Brewers Association of the Americas’ Award of Merit and the Brewers Association’s Recognition Award. He is an elected fellow of the Institute of Brewing & Distilling. He is also a recipient of the UC Davis Distinguished Teaching Award.

If it's good enough for him it's good enough for me.

I will quote my quote for those who don't think pitch rates matter.