A brand new yeast starter calculator

[homebrewdad]

Here's a labor of love that I hope you find useful - my new yeast starter calculator.

Like any good starter calculator, it will help you figure your yeast viability and what size starter you need to hit your desired cell count.

Unlike other calculators, this one allows you to "overbuild" your starter - i.e. to add in an extra number of cells that you intend to harvest for a future brew date.

Also, unlike other calculators, this one automatically figures subsequent steps for you until your desired cell count is achieved (up to four total steps).

I hope that you enjoy. Feedback is of course welcomed.

edit: new feature update!

I just added the ability for you to specify your own custom pitch rate, as opposed to picking only from ale (.75 million cells/ml), lager (1.5 million cells/ml), or hybrid (1 million cells/ml).

edit: another feature update!

Calculator now does a better job of optimizing steps, thus leading to less overall wort needed in multi step starters.

 

[flars]

I like it. I'll make some comparisons with the calculator I normally use, and my brewing notes, when I'm preparing to brew again.

 

[homebrewdad]

Thanks, I hope that you find it to be useful.

 

[NoahBeach]

Awesome! Really like the auto step logic and built in harvest addition.

Only thing that does not make perfect sense to me at a quick glance is the "overbuild harvest" at the bottom, are these numbers for after cold crashing/decanting? I ran 5.5G of ale at 1.051, harvest 100B cells, 90% viability on 100B cells. Gave me 1.5L starter to produce 302B cells, but the "overbuild harvest" total (pitch + harvest) = 500ml, where did the other 1L go?

Thanks and bookmarked!

 

[homebrewdad]

Awesome! Really like the auto step logic and built in harvest addition.

Only thing that does not make perfect sense to me at a quick glance is the "overbuild harvest" at the bottom, are these numbers for after cold crashing/decanting? I ran 5.5G of ale at 1.051, harvest 100B cells, 90% viability on 100B cells. Gave me 1.5L starter to produce 302B cells, but the "overbuild harvest" total (pitch + harvest) = 500ml, where did the other 1L go?

Thanks and bookmarked!

Understand that on the overbuild, it does assume that you have a homogenous mixture.

It projected 302 billion cells for you total, with 100 billion as your overbuild.

100/302 = 33.11% of your total cells.

So, 33.11% of your 1.5 liter starter is just a fuzz over 500ml. That is what you harvest to save for your next brew date. The other full liter, you pitch into your beer.

That's why there are two columns. "Amount to pitch" and "Amount to harvest".

 

[ABVIBUSRM]

i ran my numbers into brewers friend then through yeastcalc both were the same ..then i ran it through this one and it was off..im stickn with mr malty,yeastcalc or brewers friend

 

[homebrewdad]

i ran my numbers into brewers friend then through yeastcalc both were the same ..then i ran it through this one and it was off..im stickn with mr malty,yeastcalc or brewers friend

My numbers will be drastically different than Mr. Malty. I explain that on the page below the calculator; I exclusively use the Kai Troester formulae for estimating yeast growth.

 

[ABVIBUSRM]

My numbers will be drastically different than Mr. Malty. I explain that on the page below the calculator; I exclusively use the Kai Troester formulae for estimating yeast growth.

Im sure its a excellent calculator i'll check it out again except read the page this time

 

[homebrewdad]

Im sure its a excellent calculator i'll check it out again except read the page this time

No offense taken. If there are legit issues, I absolutely want to know about them!

 

[ABVIBUSRM]

No offense taken. If there are legit issues, I absolutely want to know about them!

Can you explain what Kai Troester formula is? not familiar

 

[homebrewdad]

Can you explain what Kai Troester formula is? not familiar

Sure. Kai Troester (Braukaiser.com) is a guy who has done a ton of scientific research related to homebrewing. Here's one of his more in depth posts on the subject.

There has been some question for some time about the Mr. Malty numbers, as they seem to be okay for simple (non agitated) starters. They scale up a bit for shaken, but the stirred numbers are very conservative - and, it seems, are based on just projecting the original formula (not on actual cell counts after stirring).

Troester did research on cell growth and found that while his simple starter numbers were similar, when he actually counted cells from a stirred starter, the output was MUCH higher than what Mr. Malty projects. He has repeated the experiment with similar results - his 2013 NHC presentation has an even higher measured growth rate than I use in my calculator.

Specifically, the growth equations used are, as follows:

For stirred starters, if the initial cell count is less than 1.4 billion per gram of extract, the growth rate is 1.4 billion cells per gram of extract.
If the initial cell count is between 1.4 billion and 3.5 billion per gram of extract, the growth rate is 2.33 - (.67 * initial cells) billion cells per gram of extract.
If the initial cell count is greater than 3.5 billion per gram of extract, there is no growth.

For simple (non agitated starters), the growth rate is .4 billion cells per gram of extract, up to an inoculation rate of 3.5 billion cells per gram of extract. If you exceed this, there is no growth.

For shaken starters, the growth rate is .62 billion cells per gram of extract, up to an inoculation rate of 3.5 billion cells per gram of extract. If you exceed this, there is no growth.

 

[ABVIBUSRM]

Sure. Kai Troester (Braukaiser.com) is a guy who has done a ton of scientific research related to homebrewing. Here's one of his more in depth posts on the subject.

There has been some question for some time about the Mr. Malty numbers, as they seem to be okay for simple (non agitated) starters. They scale up a bit for shaken, but the stirred numbers are very conservative - and, it seems, are based on just projecting the original formula (not on actual cell counts after stirring).

Troester did research on cell growth and found that while his simple starter numbers were similar, when he actually counted cells from a stirred starter, the output was MUCH higher than what Mr. Malty projects. He has repeated the experiment with similar results - his 2013 NHC presentation has an even higher measured growth rate than I use in my calculator.

Specifically, the growth equations used are, as follows:

For stirred starters, if the initial cell count is less than 1.4 billion per gram of extract, the growth rate is 1.4 billion cells per gram of extract.
If the initial cell count is between 1.4 billion and 3.5 billion per gram of extract, the growth rate is 2.33 - (.67 * initial cells) billion cells per gram of extract.
If the initial cell count is greater than 3.5 billion per gram of extract, there is no growth.

For simple (non agitated starters), the growth rate is .4 billion cells per gram of extract, up to an inoculation rate of 3.5 billion cells per gram of extract. If you exceed this, there is no growth.

For shaken starters, the growth rate is .62 billion cells per gram of extract, up to an inoculation rate of 3.5 billion cells per gram of extract. If you exceed this, there is no growth.

Thanks alot for the info

 

[homebrewdad]

Thanks alot for the info

Happy to help.

 

[thekraken]

Cool.

Can you explain to a rookie what am I supposed to do between steps? For example: 5 gallon batch, 1.080 og, 0 overbuild, 1 liter flask size, stir plates. This creates two steps, I understand the first step, how do I get to the second?

 

[FourSeasonAngler]

This is great! I will give it a shot this week for my brewday Sunday!

 

[homebrewdad]

Cool.

Can you explain to a rookie what am I supposed to do between steps? For example: 5 gallon batch, 1.080 og, 0 overbuild, 1 liter flask size, stir plates. This creates two steps, I understand the first step, how do I get to the second?

No problem.

Chill your first starter once it's done - at least overnight. This will make the yeast flocc out and form a solid layer on the bottom of the flask (some yeast varieties require a longer cold crash than do others). Decant most of (i.e. gently pour it out until almost all of the clear liquid is gone, being careful to not pour out the solid yeast).

Now, go boil up your new starter solution on your stovetop. Allow the original step to warm back up to room temps while you are cooling the new down, then pour the new starter wort down right on top of the yeast. Stick it back on the stirplate.

 

[thekraken]

No problem.

Chill your first starter once it's done - at least overnight. This will make the yeast flocc out and form a solid layer on the bottom of the flask (some yeast varieties require a longer cold crash than do others). Decant most of (i.e. gently pour it out until almost all of the clear liquid is gone, being careful to not pour out the solid yeast).

Now, go boil up your new starter solution on your stovetop. Allow the original step to warm back up to room temps while you are cooling the new down, then pour the new starter wort down right on top of the yeast. Stick it back on the stirplate.

So in your calcs you estimate how much volume will be decanted each step? I assume it's the starter solution gravity is the same for each step? Or should the gravity be somehow adjusted between steps to compensate for the growing inoculation rates?

Also, how long do you let the starters go for each method of aeration?

A starter scheduler might be a nice feature for your calculator.

 

[homebrewdad]

So in your calcs you estimate how much volume will be decanted each step? I assume it's the same solution for the starter is the same gravity for each step? Or should the gravity be somehow adjusted between steps to compensate for the growing inoculation rates?

Also, how long do you let the starters go for each method of aeration?

A starter scheduler might be a nice feature for your calculator.

Basically, I'm assuming that you are adding the full amount of any subsequent steps to your leftover yeast slurry/wort from the previous step. It's not enough of a factor to worry about the exact amount that you have left, especially since the Troester methods key on the amount of available extract more than they do total volume.

I personally let starters go 2-3 days per step, but that's likely overdoing it. Smaller starters especially can be completely done in a day.

A scheduler is not a bad idea; I could see adding this as a future enhancement.

 

[thekraken]

Good work. I'll be doing my first starter pretty soon, I'll go by your calculator. I'll let you know how it goes.

Some final questions: what am I to do with the overbuild, freezer or fridge? And what rates should I then figure for viability?

 

[homebrewdad]

Good work. I'll be doing my first starter pretty soon, I'll go buy your calculator. I'll let you know how it goes.

Some final questions: what am I to do with the overbuild, freezer or fridge? And what rates should I then figure for viability?

lol... I'm guessing that was a typo. No need to "buy" it, it's free.

Fridge for overbuild unless you are planning to add glycerine. Freezing causes yeast cells to expand and cell walls to burst, which leads to death.

I personally use the same 20% per month calculation. So next time you go make a starter, use the harvest date as your production date. There's evidence that home harvested yeast is not quite as viable as lab yeast, but I've never had an issue with this method.

Just know that once your yeast gets in the 4-6 month old range, you should plan to make a starter to keep it healthy, even if you are not planning to brew with it for a while.

 

[thekraken]

lol... I'm guessing that was a typo. No need to "buy" it, it's free.

Ahh dang, you saw that! I was hoping I edited it before anyone noticed.

 

[homebrewdad]

Ahh dang, you saw that! I was hoping I edited it before anyone noticed.

Psh, no worries. I could simply see somebody going and saying, "man, that a-hole homebrewdad is such a sellout. He wants people to pay to use his stupid calculator!"

 

[testingapril]

lol... I'm guessing that was a typo. No need to "buy" it, it's free.

Fridge for overbuild unless you are planning to add glycerine. Freezing causes yeast cells to expand and cell walls to burst, which leads to death.

I personally use the same 20% per month calculation. So next time you go make a starter, use the harvest date as your production date. There's evidence that home harvested yeast is not quite as viable as lab yeast, but I've never had an issue with this method.

Just know that once your yeast gets in the 4-6 month old range, you should plan to make a starter to keep it healthy, even if you are not planning to brew with it for a while.

FTFY in bold.

 

[homebrewdad]

FTFY in bold.

Durr. I just bought more of the stupid stuff. That's what I get for trying to make tons of posts while theoretically also trying to work.

Edited the post in question, thanks.

 

[eric19312]

I like it!

Thanks for doing this. Here is a feature suggestion that would be nice:
A calculator for determining White labs manufactured on date. Subtracting months I always end up counting on fingers or breaking out Excel. Dont know why but that stupid date drives me nuts. It would be nice to have toggle button for yeast source, along with calendar for "date on package".

Guess that could get complicated with more liquid yeast manufacturers showing up all the time.

But it is easy to see that the most important number is the viability of the yeast in your hand when you start. The manufacturers of the yeast should really provide a viability calculator on their web pages.

 

[eric19312]

Oh and that inoculation rate calculation is fantastic. I finally understand logic of stepping up.

 

[eric19312]

ok one more..

Shouldn't the overbuild harvest be coming from the last step? It seems to be collected from the first step in the calculator.

 

[homebrewdad]

Re: the calendar date - I may consider adding this, I can see the value.

Re: the overbuild - this amount is factored in all along. If the calculator can get you to your desired amount for brewing + the overbuild in one step, it will. If not, it keeps going until that it done. However, the overbuilt cells should be deducted from the final step.

I have tested this with different sized steps, but if you are seeing a bug (or think that you might), please do not hesitate to let me know. To reproduce the issue, I'll need to know all of your numbers for the top three steps - your wort details, your yeast details, and your starter details.

 

[homebrewdad]

Feature update: I just added the ability for you to specify your own custom pitch rate, as opposed to picking only from ale (.75 million cells/ml), lager (1.5 million cells/ml), or hybrid (1 million cells/ml).

 

[eric19312]

Re: the overbuild - this amount is factored in all along. If the calculator can get you to your desired amount for brewing + the overbuild in one step, it will. If not, it keeps going until that it done. However, the overbuilt cells should be deducted from the final step.

Ale
11 gal batch
1.070 wort
100 billion overbuild
yeast production Oct 1
4 liter flask

I get a two step process, second step is 2.5 liters. But only tells me what to do with 2 of the liters... 1.831 liters into batch, 0.169 liters for the overbuild.