Yeast growth calculator?

Is there a calculator that will show you how much yeast you are producing based on size of starter, mfg date etc?

Essentially like Mr Malty but you punch in size of starter etc and it will show you how many cells you can expect?

+1 I'd also like this for growing starters up in steps. Usually I just manipulate Jamil's calculator

There's a chart in "Yeast" for regular starters... I think you multiply by 2 if you use a stir plate.

I found I made a calculator that worked for making starters and it produced the same numbers for a given condition as MrMalty. So reversing the formula is not hard, the basis for the numbers was the maltosefalcon website on yeast maintenance and propagation. What you are asking for is really easy there is a section in there that describes the number of yeast cells in a given starter (assuming small steps ie 10fold or less) for it is something like 20MYC per ml traditional 60 shaken 92 for intermittent aeration and 180-360 for stirplate. So just take these numbers and multiple them by the size of your starter in milliliters

Clem

Nothing like that can actually be accurate enough though. It will just be a wild ass guess. Would be akin to you just guessing how much is multiplied by you dumping it into a 1L starter from a smack pack. Time, temp, actual viability, and SG will also NEED to play into it. To name but a few variables.

suprchunk said:

Nothing like that can actually be accurate enough though. It will just be a wild ass guess. Would be akin to you just guessing how much is multiplied by you dumping it into a 1L starter from a smack pack. Time, temp, actual viability, and SG will also NEED to play into it. To name but a few variables.

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Totally agree!

But then everything but a roll call is a wild ass guess! The article does back it self up with saying these are averages, time, temp and SG, nutrient level are specified. Viability is assumed at near 100% in the article so if you allow for that you would have better than no idea, but it is essentially an educated guess.

Clem

Clementine said:

I found I made a calculator that worked for making starters and it produced the same numbers for a given condition as MrMalty. So reversing the formula is not hard, the basis for the numbers was the maltosefalcon website on yeast maintenance and propagation. What you are asking for is really easy there is a section in there that describes the number of yeast cells in a given starter (assuming small steps ie 10fold or less) for it is something like 20MYC per ml traditional 60 shaken 92 for intermittent aeration and 180-360 for stirplate. So just take these numbers and multiple them by the size of your starter in milliliters

Clem

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This method will give you some rough numbers, but is not very accurate. The connection between the ratio of Step 1 (in mL) to Step 2 (in mL) is not quite a 1:1 proportional ratio with the resulting yeast. What I am trying to say is that if you have a 100mL step, and step up to a 2000mL, it is not 2x as much yeast as if you went from 100mL->1000mL. It is actually a very complex growth curve that is not entirely understoood.

There are a few charts on the internet that show what some expected results would be, but those are based off of averaging the results from experiments in the lab, not from some sort of formula. That is one benefit of using a smackpack or vial, you can have more certainty regarding your final yeast population since you are only making one step. When culturing from home stocks, you have to kind of aknowledge the fact that you are dealing with an unknown yeast cell count unless you have a microscope.

theredben said:

This method will give you some rough numbers, but is not very accurate. The connection between the ratio of Step 1 (in mL) to Step 2 (in mL) is not quite a 1:1 proportional ratio with the resulting yeast. What I am trying to say is that if you have a 100mL step, and step up to a 2000mL, it is not 2x as much yeast as if you went from 100mL->1000mL. It is actually a very complex growth curve that is not entirely understoood.

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Agreed more depends of the availability of nutrients, O2 and sugar than size of starter. The only reason the size of the starter even matters is to get enough sugar/nutrients and O2 into a small starter results in too high concentrations of these items that can become toxic for the yeast. Hence larger starter is kinder on them but not if you make the steps too big as then bacteria can get a foothold before the yeast has a chance If you read articles about stepping up yeast they recommend no greater than x10 steps most brewing schools teach X8 US x5 UK and X4 German step in starters.

Clem

Clementine said:

Totally agree!

But then everything but a roll call is a wild ass guess! The article does back it self up with saying these are averages, time, temp and SG, nutrient level are specified. Viability is assumed at near 100% in the article so if you allow for that you would have better than no idea, but it is essentially an educated guess.

Clem

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Very true. I'd rather not worry about it. Because if I did worry about it I would find myself buying more equipment that I would use infrequently. Or I would use it frequently and piss the wife off.

suprchunk said:

Or I would use it frequently and piss the wife off.

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Sounds like a good reason to do it well that and the old golden rule he who dies with the most tools wins!

I've been doing lots of reading on yeast trying to figure out a accurate way to approximate yeast numbers. There is not much out there other than that untamed ass we have been talking about.


Clem

You can get the lab equipment to count cells. Over the course of a few trials you can approximate the cell count. It would still be just an approximation, or guess, of how many you actually have. I don't think it would be so far off that you wouldn't be close enough.

If you know your cell doubling time and initial cell density it's simple to get an estimate. But to be more precise, a hemocytometer is necessary along with a P10 pipette.

N=N0*2^(t/g)

N=final cell count
N0 = initial cell count
t = incubation time
g = doubling time

Dhruv6911 - That formula is almost useless for the homebrewer. They have no accurate way to determine doubling time, nor do they have any idea how long the actual incubation took. Just because you leave a starter on a stirplate for 72 hours, that does not mean the yeast population is growing that entire time.

As stated before, there are some rough guidelines available on the web, but beyond that you need a microscope to determine actual cell counts. OTOH, If you always use a certain sized starter and it works for you, that is all that counts. It is not like those "official" numbers of cells/mL/Plato are actually based on objective science, they are really more of a rough guess based on what has worked for others.

Like most things with homebrew, RDWHAHB rules the day!

Jamil's calculator is based on formulas developed by himself emperically. I've heard his pitching rates are on the high side compared to professional brewing practices, but I'm happy with my beers using his calculator. For lagers and 10 gallon batches, you end up needing to grow up in steps to avoid buying so many smack packs/ vials. Has anyone determined the formulas based on gravity, batch size, and type of yeast (ale or lager)? I'm not so concerned about "how many cells I need" as I am "how many cells might I get with X sized starter at Y gravity using Z method"

After reading many posts like this, and asking the same questions myself, I decided to do something about it. This is the best I could come up with, please feel free to correct me on any mistakes or shortcomings you may find.
YeastCalc

Sulli, that is an amazing tool. Well done. (And very classy. You're a web designer and/or a programmer?)

I have one question -- why 50 - 100 million / ml inoculation rate? I just threw a WYeast pack into 4.5 L and after fermenting and decanting froze some of the slurry in glycerine... Was that a mistake?

Sulli said:

After reading many posts like this, and asking the same questions myself, I decided to do something about it. This is the best I could come up with, please feel free to correct me on any mistakes or shortcomings you may find.
YeastCalc

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I see that you just add new cells to the original cell count. I thought, but could be wrong, that some adjustment had to be made for some die off, or unviable yeast cells. Is that already accounted for in your "new cells created"?

Kurisu said:

Sulli, that is an amazing tool. Well done. (And very classy. You're a web designer and/or a programmer?)

I have one question -- why 50 - 100 million / ml inoculation rate? I just threw a WYeast pack into 4.5 L and after fermenting and decanting froze some of the slurry in glycerine... Was that a mistake?

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"The most important thing to know about starter size is that the inoculation rate affects the rate of growth. In other words, the "pitching rate" of your starter has a big effect on the amount of new yeast cells you will see from any propagation. It is not the volume of the starter that is important, but how many cells you add in relation to that volume. Too high an inoculation rate, and you get very little growth. If you use too low an inoculation rate, then you are not really making a starter, you are fermenting beer. Just as the pitching rate affects growth in a batch of beer, which is important to beer flavor; it also affects growth in a starter, except in the case of a starter you are not concerned about flavor, you are concerned about the health of the yeast and maximizing your growth rate.
Ideally, you want to grow your yeast in a large enough volume of wort to ensure optimal yeast health and to get a decent amount of growth for your trouble."
C.White and J.Zainasheff, "Yeast: The Practical Guide to Beer Fermentation", 2010

According to what I read in Chris White's "Yeast" book, an inoculation rate of 50 - 100 million cells/ml of wort appears to be the 'sweet spot' for maximizing cell growth and health in a starter.
That said; it does not mean that if you pitch outside that range you've hurt your yeast. Perhaps I should word the tool tip differently, like "50 - 100 million cells/ml is the optimal range to maximize yeast growth", or something along those lines.

The short answer is; no, you did not make a mistake, your yeast are fine.

BTW Thanks for the props. Cheers

cwi said:

I see that you just add new cells to the original cell count. I thought, but could be wrong, that some adjustment had to be made for some die off, or unviable yeast cells. Is that already accounted for in your "new cells created"?

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It's accounted for in the initial starter, but with each subsequent step the viability should be pretty close to 100%.
However, since all online yeast calculators can be off by as much as +/- 25 billion cells, I wouldn't worry too much about the few that might, or might not, die off.

Sulli said:

It's accounted for in the initial starter, but with each subsequent step the viability should be pretty close to 100%. Since all online yeast calculators can be off by as much as +/- 25 billion cells, I wouldn't worry too much about the few that might, or might not, die off.

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I was just going off the behavior of some of the other calculators and charts. It seemed like they accounted for a significant die-off during propogation, but I never researched the background behind it, so it was probably a bad assumption. Reverse engineering their algorithms is a also little difficult, because so many jump from 1 vial to 2 vials of starter yeast. I understand why they rig them that way, but personally I would like the ability to switch to a continuous mode.

I hope it's not too late to post in this thread, but I have a question for Sulli:

It seems like the assumption in your calculator is that the wort is always 1.037. Is there a way that I can modify this assumption in the calculator? If not, can you point me to a place where I can find any equations you used that take SG into account in the calculations (or PM them to me)?

I'm asking because I'd really like the ability to vary the SG of the starter and not just the size; I'm growing some Pacman from dregs and my first two steps used 1.020 wort and not the 1.037 assumed in the calculator. From what I've been able to read so far, I've learned that yeast don't necessarily behave linearly so simply halving the outputs for each step from your model seems like a very wrong thing to do. I should probably mention that I'm very comfortable with math and creating spreadsheets/computer models, so you don't really need to worry about overwhelming me with calculations.

If any of this information is readily available, I apologize. If not, maybe we can work together a little bit to add one more thing to your already AWESOME tool (that made me delete my bookmark to Mr. Malty). Thanks for the help!

thisoneguy said:

I hope it's not too late to post in this thread, but I have a question for Sulli:

It seems like the assumption in your calculator is that the wort is always 1.037. Is there a way that I can modify this assumption in the calculator? If not, can you point me to a place where I can find any equations you used that take SG into account in the calculations (or PM them to me)?

I'm asking because I'd really like the ability to vary the SG of the starter and not just the size; I'm growing some Pacman from dregs and my first two steps used 1.020 wort and not the 1.037 assumed in the calculator. From what I've been able to read so far, I've learned that yeast don't necessarily behave linearly so simply halving the outputs for each step from your model seems like a very wrong thing to do. I should probably mention that I'm very comfortable with math and creating spreadsheets/computer models, so you don't really need to worry about overwhelming me with calculations.

If any of this information is readily available, I apologize. If not, maybe we can work together a little bit to add one more thing to your already AWESOME tool (that made me delete my bookmark to Mr. Malty). Thanks for the help!

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I'm glad that you've found my calculator useful. I've tried to make it as accurate as is possible with using only math formulas to determine cell counts, but with all the variables involved in yeast propagation, a calculator can really only give you a ball-park figure. It's no substitute for a hemacytometer and a good microscope.
The calculations in YeastCalc are based on data that I acquired from Chris Whites Yeast book, which I then cross checked with Mr. Malty; YeastCalc is not really designed to accommodate propagation of such small volumes. How are you determining what your initial cell count is?
I'm not sure that halving the amount of sugar in the wort is going to necessarily decrease the growth rate of the yeast cells, especially with the small volumes involved in propagating the dregs from a bottle [maybe someone more knowledgeable about this could chime in], but it will definitely give them an environment that is much less stressful, which is what you want when dealing with old or weak cells, i.e. dregs. What kind of volumes are you using to propagate the dregs?

For the initial cell counts, I referred to somebody's post about getting ~300 million cells from the dregs of a two-hearted bottle (I'm on my phone at work, so I'm not able to do too much more searching for a reference right now). I used the dregs from a bomber of Dad's Little Helper Black IPA and a 12 oz of Dead Guy; the black IPA had more than twice as much sediment as I see in 2HA, and the Dead Guy had a little less, so I estimated that I started with 900 million cells.

As far as volumes, I did 200 mL of 1.020, 400 mL of 1.020, 800 mL of 1.040 and now 2L of 1.040 (all using a stir plate). Ideally, I'd like to be able to chill this to let the yeast drop out and split the yeast into 2 jars - one to brew with on Monday and one to leave in the fridge for a few days that I can use to grow a starter for the following weekend.

thisoneguy, you've got me thinking today [thanks for that, I always appreciate food for thought], really the only way to know the effects of a 1.020 wort vs 1.040 wort, would be to propagate some yeast in each environment, under the same conditions, and count the cells. The problem with this, is that I haven't the equipment to do it. But...One could measure the amount of slurry produced from each starter and probably get a fair idea of the difference [if any] in cell production. I don't think the growth rate is going to change, but they are going to deplete their food resources sooner, and this might lower the number of cells produced. [I think this is what you were getting at in your earlier post]. Anyway I was thinking of making another version of YeastCalc specifically designed for smaller volumes and cell counts. I've already had several conversations in other forums with guys starting from slants or plates who are looking for something similar, and I have no doubt that a mathematical formula can be made that will calculate [roughly] the growth curve of a yeast cell. The biggest problem I see with it though, lies in determining what your initial cell count is. Your saying that you might get 300 million cells from the dregs of a bottle of Two-Hearted Ale, but the question then becomes, how many of those 300 million cells are actually viable? Without a microscope and some methylene blue, your shooting in the dark. Even White Labs doesn't claim to have exactly 100 billion cells in a vial of yeast, they actually claim 70 - 140 billion, 70 billion cells is a pretty big discrepancy [plug the two different numbers into yeastcalc and check out the final cell counts, huge difference with a stir plate]. So, really, in order for the calculator [any calculator] to work well, your initial cell count needs to be fairly accurate. Anyway I'm just rambling now. But yeah it would be cool to make a scaled down version of YeastCalc. It might require some experimentation, but that's what homebrewing is all about. I'm game.
Cheers.

thisoneguy said:

For the initial cell counts, I referred to somebody's post about getting ~300 million cells from the dregs of a two-hearted bottle (I'm on my phone at work, so I'm not able to do too much more searching for a reference right now). I used the dregs from a bomber of Dad's Little Helper Black IPA and a 12 oz of Dead Guy; the black IPA had more than twice as much sediment as I see in 2HA, and the Dead Guy had a little less, so I estimated that I started with 900 million cells.

As far as volumes, I did 200 mL of 1.020, 400 mL of 1.020, 800 mL of 1.040 and now 2L of 1.040 (all using a stir plate). Ideally, I'd like to be able to chill this to let the yeast drop out and split the yeast into 2 jars - one to brew with on Monday and one to leave in the fridge for a few days that I can use to grow a starter for the following weekend.

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I'm curious as to how much yeast slurry you end up with, would you post your results when it's done?

I'll definitely post the results. The 2L step is in the fridge right now helping the yeast fall out. I have kind of a busy weekend, so I'll post sometime between late tonight or Sunday morning

After chilling, it looks like I have about 38 mL of thick yeast slurry (a little looser than a white labs vial) based on 2 different ways of estimating. Both ways get to the same place, but i'll try to get a more reliable number soon.

Nice! Congratulations on successful propagation from a bottle.
So if we assume a yeast cell density of about 4.5 billion/ml, and that's probably being generous [ala Mr. Malty].
You've grown approximately 171 billions cells, which is about half of what YeastCalc predicted. This tells me you didn't have anywhere near 900 million cells to start with. In fact you probably started with less than 100 million viable cells; but now that you have a quantifiable amount of yeast to work with, the calculator can help you determine how to step it from here, and you know it's pretty close to 100% viable as well.
Also, I did some reading on propagating yeast from a bottle. White recommends starting with a volume of 10-25 milliliters of 1.020 wort, and after the first growth you can switch to a more concentrated wort, like 1.040. I assume this is because after the first growth they have regained their vitality.

I'm happy it worked! Not bad for my first try; if it's beginner's luck, I can't complain. :rockin:

Next time I culture from a bottle, I'll be a little better equipped. I got some smaller Erlenmeyer flasks (125, 250, and 500 mL in addition to my 1L and 2L) so smaller quantities will be easier to work with. I think I may have actually underestimated the volume in my last post, but I'm still going to do another small step up before brewing tomorrow (5.5 gallons of 1.065, so 171B cells is a little light). I might end up overpitching a little, but that's a chance I'm going to take.

To get a more accurate volume, I marked the level that the yeast was at yesterday, and I'll pour that amount of water into a smaller flask (or graduated cylinder if I have one laying around) after I use this starter in tomorrow's brew. Tomorrow night I'll post a better estimate.

I was thinking about washing this yeast after my batch ferments out, but I'm tempted to just do this again (start from dregs) just to get some practice doing it.

A recycled White Labs vial would work well for the first growth, they have a total volume of 47 milliliters. You could measure up in 10 mil increments and mark it on the side of the vial, then you would have a pretty good idea of how much yeast you have in the vial after it ferments out. Just a thought.
From there you could step up to either 125 or 250.
I've never cultured up yeast from the dregs of a bottle, but discussing all this with you has got me thinking it would be interesting to give it a try.

I'll have to try that. As it turns out, what I thought was yeast in the starter must have been trub or undissolved DME...

After pitching into my IPA, there was no activity at all after 3 days (verified by gravity reading). I ended up pitching some Notty instead. I'm going to try to harvest again soon, but probably Bell's yeast; I ended up ordering a smack pack of Pacman.

Bummer man. Better luck next time.

Sulli said:

After reading many posts like this, and asking the same questions myself, I decided to do something about it. This is the best I could come up with, please feel free to correct me on any mistakes or shortcomings you may find.
YeastCalc

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You calculator is awesome and I use it all the time. Thanks for taking the time to put it together.

bmbigda said:

You calculator is awesome and I use it all the time. Thanks for taking the time to put it together.

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Glad you like it! Thank You.