Stepped Yeast Starter Calculator

[puffer555]

I have always generally used Mr Malty's pitching rate calculator to calculate the volume of starter required for a specific OG and batch size: http://www.mrmalty.com/calc/calc.html

However, considering that I now subdivide my yeast packs into 5 x 20 ml tubes, I have been wondering how to properly step up a yeast starter to achieve the recommended pitching rates.

I know a lot of people advocate the use of stepped starters, however, after some reading, I get the feeling that most people just wing it with regards to volumes and cell counts. Most seem to keep to the basic rule of a max 10 fold increase in volume, however the actual pitching rates after multiple steps are anyone's guess.

Anyway, I have been working on a spreadsheet that allows you to calculate the amount of yeast grown in a stepped starter.

Essentially I played around with Mr Malty's yeast pitching calculator and managed to extract some of the raw data in terms of "step up ratio vs growth rate". This is essentially the scientifically determined data that most yeast calculators are based on. The spreadsheet I have developed allows you to input the starting yeast volume and the step up starter sizes and it determines final yeast count at the end of each step.

Note - At this stage, the spreadsheet is only a draft. I am sure I will get plenty of feedback (good and bad) which I am sure will change some things. Note that it is also only based on a "stir plate" starter at this stage

View attachment Stepped_Starter_Calculator.xlsx

To explain the workings of the spreadsheet I thought a quick explanation with an example may help.

Let's say I have 20 ml of 3 month old yeast in the fridge. I have assumed that the yeast has a 50% viability. This will depend on many factors, but lets assume 50 % (it can be changed in the spreadsheet anyway).

I want to make a 44 L batch of 1.065 Ale. Mr Malty says that I need 523 Billion yeast cells for a correct pitching rate.

I then set up the spreadsheet follows:

Step 1:
Original yeast volume 20 ml

Viability - 50%

o This calculates as 10 billion viable yeast cells or 10 ml of viable yeast (50% of the original 20 ml).

Starter Volume 100 ml

o This is a step up ratio of 10 (10 ml of yeast into 100 ml of wort)

o A max of 10 is recommended by some sources, but some use 5, and some use more.

o I try to stick to around 10 for each step.

o Note that a step up ratio below 4 will currently not work, as I don't have any data for below 4.

The step up ratio is then used to determine the growth rate (based on the data extracted from Mr Malty).

Final yeast count at end of first step is then 23.167 billion cells (or 23.167 ml of yeast)

Step 2:

Wort Addition 150 ml

o This is adding 150 ml of fresh 1.060 wort to the same starter (to give 250 ml of 1.040 total volume)

o The spreadsheet calculates the required OG of the addition for you to achieve 1.040.

o This achieves the same result as decanting off the spent wort (beer) and filling with 250 ml of 1.040 wort. It just saves a lot of mucking around.

o Note that the fermented starter is also assumed to have a FG of 1.010

23.167 ml into 250 ml is a step up ratio of 10.8

Final yeast count is 55.340 billion (55.340 ml)

Step 3:

Wort Addition 300 ml (1.065 Wort which gives a 550 ml starter).

Step up ratio of 9.9 which achieves 127.63 billion cells

Step 4:

Wort Addition 600 ml (1.068 Wort which gives a 1150 ml starter).

Step up ratio of 9 which achieves 282.49 billion cells

Step 5:

Wort Addition 600 ml (1.098 Wort which gives a 1750 ml starter).

Step up ratio of 6.2 which achieves 531 billion cells CLOSE ENOUGH !!

So essentially, for a given staring yeast volume and viability, I just play with my wort additions to achieve:

A step up of around 10 or less

the recommended pitching rate after as few step ups as possible.

Just to convince the sceptics, the spreadsheet predicts the same results as Mr Malty does (within 10 %). This can be verified (in an arse about face way) by doing the following:

In Mr Malty Put in the following data:

25 L of 1.055 Ale with a single pack of 70 % viable yeast (I'm using random numbers to demonstrate).

Mr Malty recommends a pitching rate of 253 Billion cells, and a "stirred" starter of 1.96 L

In the spreadsheet this can be verified by using the first step up calculator.

Put a 100 ml of yeast at 70% viability into a 1960 ml starter

Final cell count is 255 Billion cells which is pretty much the same as Mr Malty

Or for a similar check:

Put in the following data into Mr Malty:

40 L of 1.080 Lager with 80 % viable yeast

Mr Malty recommends a pitching rate of 1155 Billion cells, and a "stirred" starter of 12.99 L with three packs of yeast.

In the spreadsheet this can again be verified by using the first step up calculator.

Put 300 ml of yeast (3 packs of yeast) at 80% viability into a 12990 ml starter

Final cell count is 1159 Billion cells which is again pretty much the same as Mr Malty

The main reason for the small difference is that I only have discrete data points for the "step up ratio vs growth rate". The unknown data is determined through linear interpolation between the data points which gives a small amount of error.

Anyway, hopefully I haven't confused you all. The spreadsheet is in a draft stage, but seems to work as expected, and could be a good tool for me and hopefully others. I am hoping for some independent verification of the methods as well as the spread sheet. A few short comings thus far such as, only for stirred starters, and growth rates for step ups below 4 times are very hard to find.

Anyway, feel free to comment good or bad. Any potential improvements will also be noted.

 

[puffer555]

Sorry for the long post and formatting. Typed it in Word.
Anyway, looking forward to you replies.

Regards
Tim

 

[felten]

A little OT but the yeast book has a lot of great info on this kind of stuff, well worth a read. (if you don't have it already)

 

[stux]

Would the remaining diluted alcohol that you're leaving in your starter at each stage by not pouring off the "beer" have any affect on the yeast viability/health?

My thoughts are that ideally a starter is made in a close to zero alcohol environment, but you actually end up with a slightly alcoholic environment... and perhaps that might cause the yeastybites to skip some earlier stages of their development?

I don't know enough about yeast propogation to actually say

 

[puffer555]

A little OT but the yeast book has a lot of great info on this kind of stuff, well worth a read. (if you don't have it already)

Thanks for the reply. Yeah I did buy and read it. Well worth it. It has opened my eyes somewhat to yeast management.
It is one of the main reasons why I am trying to get the right pitching rate for my beers.
The book does cover stepping up of yeast, but only in brief and not from a smaller yeast volume scenario.
It also doesn't give a quantitative method for determining growth.
Hence the spreadsheet.

Would the remaining diluted alcohol that you're leaving in your starter at each stage by not pouring off the "beer" have any affect on the yeast viability/health?

Very good point, and one I didn't think about.
It makes more sense to drain each step and replace with alcohol free wort.
Much better for yeast health.
I was just aiming to minimise handling of the yeast,, and hence minimise chance for contamination.
As long as the step up ratio is the same, the amount of yeast grown should not change.

Thanks for you comments.

 

[Wolfy]

Essentially I played around with Mr Malty's yeast pitching calculator and managed to extract some of the raw data in terms of "step up ratio vs growth rate". This is essentially the scientifically determined data that most yeast calculators are based on.

I believe the MrMalty calculations are based on the formula's in Designing Great Beers and then adjusted according to information provided by Whitelabs and Wyeast (but I've not read the yeast book yet, and that may have newer/better/more detailed formula's).

Your spreadsheet is a really good idea, but I'd be curious as to how different the results are to using MrMalty.

 

[puffer555]

I believe the MrMalty calculations are based on the formula's in Designing Great Beers and then adjusted according to information provided by Whitelabs and Wyeast (but I've not read the yeast book yet, and that may have newer/better/more detailed formula's).

Your spreadsheet is a really good idea, but I'd be curious as to how different the results are to using MrMalty.

Thanks for your reply.
The spreadsheet produces the same results as Mr Malty, just in a different way.
I tried to demonstrate this in the first post.

The difference is that Mr Malty tells you what size starter to use to achieve a given yeast cell count.
The spreadsheet tells you what yeast cell count is achieved from a given starter size.
In Mr Malty, I could put in 20 % viability for the yeast (which is 20 ml), but it tells me to use multple packs of this in a huge starter which is not what I want to know.
If I want to step up however, the spreadsheet (based on the same raw data as Mr Malty) tells me how much yeast I'll get at each step.
Just seems more logical to me, for stepping anyway.

Anyway, keep the feedback coming.
Thanks for your replies so far.

 

[Thirsty Boy]

I believe the MrMalty calculations are based on the formula's in Designing Great Beers and then adjusted according to information provided by Whitelabs and Wyeast (but I've not read the yeast book yet, and that may have newer/better/more detailed formula's).

Your spreadsheet is a really good idea, but I'd be curious as to how different the results are to using MrMalty.

I talked to chris white at ANHC about stepping up, in my case, specifically about doing so from slants. The rule of thumb he gave me is that the cell density in a starter will max out at around 100million cells per ml - assuming that the original pitching rate was around 10million cells per ml. So thats the 10x increase thing.

So going from a slant into 10ml gives you 1000million cells - multiply the volume by ten times and pitch the cells into 100ml & that equals a pitching rate of 10million cells per ml, which will grow to 100ml cells per ml or 10billion cells in the 100ml. Multiply the volumes by 10 again and go to 1L, pitch in your 10billion cells (still = 10milion cells per ml pitching rate) and that will grow to 100billion cells total - which is equal to a fresh wyeast or whitelabs pack and you can use Mr Malty from there if you dont want to continue with the maths.

Thats for ales cultured at warmer temps - for lagers cultured at cooler temps, you still end up with a cell density of 100million cells per ml - but you need to double the pitching rate to 20million cells per ml - so thats using fivefold increases. So to end up with basically a fresh smack pack/vials worth of cells you would go....

10ml from slant (1 bilion cells) - into 50ml starter (grows to 5billion cells) - into 250ml starter (grows to 25billion cells) - into 1L (grows to 100billion cells)

If you happen to pitch more cells initially, you wont really end up with more than the 100million cells per ml, but pitching less and increasing more than 5x for lagers 10x for ales can result in both less cells and/or less healthy yeast at the end. So pitching say your 20ml of split up pack... You'd pitch it into the next sized up increment (so using the 20ml eg - 100ml for ale, 50ml for lager) and then it would result in the same raw number of cells that that sized culture would have given whether it came originally from a slant or whatever other source.

So according to my understanding of what Mr White said, thats pretty much how to work it out from scratch - a spreadsheet to do the math and to work out the gravity and volume of wort you need to hit the next step... That would/will be pretty handy. Of couse, I suspect if you reverse engineer it from mr malty, the numbers will all end up pretty close, so i hope this info helps rather than confuses the development of that spreadsheet.

Cheers, well done.

TB

 

[outbreak]

Cheers for that post Thirsty Boy, it answered a lot of questions that I had been meaning to ask.

 

[puffer555]

I talked to chris white at ANHC about stepping up, in my case, specifically about doing so from slants. The rule of thumb he gave me is that the cell density in a starter will max out at around 100million cells per ml - assuming that the original pitching rate was around 10million cells per ml. So thats the 10x increase thing.

So going from a slant into 10ml gives you 1000million cells - multiply the volume by ten times and pitch the cells into 100ml & that equals a pitching rate of 10million cells per ml, which will grow to 100ml cells per ml or 10billion cells in the 100ml. Multiply the volumes by 10 again and go to 1L, pitch in your 10billion cells (still = 10milion cells per ml pitching rate) and that will grow to 100billion cells total - which is equal to a fresh wyeast or whitelabs pack and you can use Mr Malty from there if you dont want to continue with the maths.

Thats for ales cultured at warmer temps - for lagers cultured at cooler temps, you still end up with a cell density of 100million cells per ml - but you need to double the pitching rate to 20million cells per ml - so thats using fivefold increases. So to end up with basically a fresh smack pack/vials worth of cells you would go....

10ml from slant (1 bilion cells) - into 50ml starter (grows to 5billion cells) - into 250ml starter (grows to 25billion cells) - into 1L (grows to 100billion cells)

If you happen to pitch more cells initially, you wont really end up with more than the 100million cells per ml, but pitching less and increasing more than 5x for lagers 10x for ales can result in both less cells and/or less healthy yeast at the end. So pitching say your 20ml of split up pack... You'd pitch it into the next sized up increment (so using the 20ml eg - 100ml for ale, 50ml for lager) and then it would result in the same raw number of cells that that sized culture would have given whether it came originally from a slant or whatever other source.

So according to my understanding of what Mr White said, thats pretty much how to work it out from scratch - a spreadsheet to do the math and to work out the gravity and volume of wort you need to hit the next step... That would/will be pretty handy. Of couse, I suspect if you reverse engineer it from mr malty, the numbers will all end up pretty close, so i hope this info helps rather than confuses the development of that spreadsheet.

Cheers, well done.

TB

Thanks for your reply TB but you have slightly confused me.
After reading your post several times, I think the main thing you're saying is that starters max out at 100 million cells per ml.
Is this for a simple starter, aerated starter, or stirred starter?

The way I see it is that my 20 mls already has 20 billion cells (if its 100 % viable).
What your saying is that if I pitch it into 100 mls (5 times increase), I wont get any increase in population.
In fact, If I pitch it into 200 mls (10 times increase), i also wont get any increase in population?
Maybe your right, but it doesn't make sense to me.

According to the yeast book (Chris White co author), 1 yeast pack into 1 litre will result in 150 billion cells for a simple non stirred starter (150 million cells per litre). Mr Malty agrees with this too.

Further to this, for a full yeast pack into 1 litre using a stirred starter, Mr Malty predicts 231 billion cells (231 million per ml).

What I'm taking out of your analogy, is that yeast will max out to a number of cells per ml, as you say.
Although, from my reading, I think that they will max out at 150 million cells per ml for a simple starter and 230 million cells per ml for a stirred starter. The spreadsheet maybe already demonstrates this, but I may have to analyse the data further to see this trend.

Anyway, thanks for your post.
I suppose it just confirms my thoughts that many people have their own way of doing steps, but it doesn't necesarily produce the recomended pitching rate at the end of the day. The jury is still out on this one.
I'm happy for you to convince me further, however I have a feeling I may have changed your way of thinking.
Hopefully others find this discussion useful too.

Thanks again for your post.

regards
Tim

 

[Wolfy]

Like TB, I'm most interested in the concept of this spreadsheet to determine starter volumes when re-culturing from a slant. My previous guesstimates were (as per TB's suggestion) based on the fact that once stepped up the (second to last step of the) starter will have about the same number of viable cells as a fresh yeast pack, from which the starter volume can be calcuated via MrMalty. A more detailed spreadsheet would be nice, but I don't have a new enough version of Office to read the attached file above.

Step 2:

Wort Addition 150 ml

o This is adding 150 ml of fresh 1.060 wort to the same starter (to give 250 ml of 1.040 total volume)

o The spreadsheet calculates the required OG of the addition for you to achieve 1.040.

o This achieves the same result as decanting off the spent wort (beer) and filling with 250 ml of 1.040 wort. It just saves a lot of mucking around.

o Note that the fermented starter is also assumed to have a FG of 1.010

Step 3:
Wort Addition 300 ml (1.065 Wort which gives a 550 ml starter).

Step 4:
Wort Addition 600 ml (1.068 Wort which gives a 1150 ml starter).

Step 5:
Wort Addition 600 ml (1.098 Wort which gives a 1750 ml starter).

I'm curious about the increasing wort concentration and if the theory behind it is valid (I've not read the Yeast book so please correct me if I'm wrong).

As you say you are assuming that the starter has fully fermented at each step.
However this is not (I believe) a valid assumption given how most people make and step up starters.
The usual procedure is to keep the starter on the stir plate for 12-24 hours before stepping up.
12-24hours is (usually) long enough for maximum cell growth, but NOT for fermentation to complete - fermentation is usually only just starting at that time (but there is of course an overlap between growth and fermentation).
(Complete fermnetation would be a longer and unknown duration, most likely a few days or more and would need gravity tests to confirm.)
Hence if fermentation is only just starting when the starter is stepped up, by increasing the wort concentration at each level, you are not keeping the base gravity at 1.040 but increasing it quite dramatically and are getting into very high gravity levels not recommended for starters and that are often referenced to yeast stress and other issues.

Given that there is evidence of better yeast growth and health (assuming appropriate yeast nutrients additions and adequate oxygenation) at lower gravity, is it not a better to add each wort addition at 1.040?
This assumes and accepts that there will have been minimal fermentation and consumption of the sugars in previous steps and that the combined wort after the addition may be slightly lower than 1.040.

 

[Wolfy]

According to the yeast book (Chris White co author), 1 yeast pack into 1 litre will result in 150 billion cells for a simple non stirred starter (150 million cells per litre). Mr Malty agrees with this too.

Further to this, for a full yeast pack into 1 litre using a stirred starter, Mr Malty predicts 231 billion cells (231 million per ml).

What I'm taking out of your analogy, is that yeast will max out to a number of cells per ml, as you say.
Although, from my reading, I think that they will max out at 150 million cells per ml for a simple starter and 230 million cells per ml for a stirred starter. The spreadsheet maybe already demonstrates this, but I may have to analyse the data further to see this trend.

I have 150billion cells from a pack pitched into a 1l starter (200billion into 2l starter, 400billion 4l stepped from 1l) penciled into the back of my BCS book, most likely I got them from one of Jamil's pod-casts.
However, given the large concentration of yeast cells in a fresh smack-pack (enough for ~20l of beer), when compared to stepping up starters, I don't think it's a valid assumption to use those numbers as a basis for growth rate analysis.
The lack of nutrients in such a small starter is the limiting factor and on some of the pod-casts the White brothers even say that pitching a full pack into a small volume starter can be detrimental to yeast viability and health.
All very different to stepping up small quantities of yeast via the step-up starter process in order to grow yeast cells.

In addition the liquid in a smack pack is well fed and highly concentrated yeast-liquid, so your 20billion cells in 20ml is about 10x more concentrated than 20ml of wort inoculated from a slant. As a consequence, and based on what the White's said on various pod-casts, pitching 20ml of super concentrated yeast into a small volume of wort may actually give little to no growth, because the yeast will burn up the nutrients so quickly no growth will be achieved. The reason it does not make sense is that you are not comparing the same thing, TB is talking about the maximum cell density of yeast when grown from small samples in wort, and you are working with highly concentrated super fed yeast from a smack pack.

 

[felten]

I believe the MrMalty calculations are based on the formula's in Designing Great Beers and then adjusted according to information provided by Whitelabs and Wyeast (but I've not read the yeast book yet, and that may have newer/better/more detailed formula's).

Your spreadsheet is a really good idea, but I'd be curious as to how different the results are to using MrMalty.

He did all the cell counting himself, months and months of making starters heh.

 

[puffer555]

Wolfy,

Here is another copy of the spreadsheet for you, and others who dont have office 2007.

View attachment Stepped_Starter_Calculator.xls

I agree with you on some points you made. My assumption that the wort is fully fermented at the end of each step (24 hrs) is probably not correct. There must be some fermentation, and so the gravity of the wort will decrease, but probably not down to 1.010. As you say, only way to really tell how much fermentation is occurring is by testing. Anyway, adding the higher gravity wort may not be necessary, and it is definitely not good for yeast health. Wort additions should prob be 1.040, or maybe 1.045.

The main approach to this method is that I dont want to have to chill the starter and decant off the spent wort at the end of each step. Adding more wort to the same vessel to achieve the 1.040 minimises handling and also decreases risk of contamination. It also reduces the time from step 1 to final pitch. As stated in a previous post the alcohol that is produced may be detrimental, however, if the above is true, then not much alcohol is produced. However, if you are stepping up five times (without decanting) then the amount of alcohol contained towards the end may be worth worrying about.

Anyway, the aim of the spreadsheet was not to determine the OG of wort additions (which it does anyway), but more how much yeast growth is achieved from a given starter size and pitching rate.

As far as your analogy of highly concentrated super fed yeast from a smack pack, I disagree. If I put 1 smack pack into a litre starter (step up ratio of 10), I get 150 billion cells, or a growth rate of 1.5. Therefore, if I add my 20 ml into 200 ml, which is a step up rate of 10, I should also expect to get a growth rate of 1.5. As long as step up ratios are the same, each yeast cell will have the same amount of wort to use and grow.

As far as stepping from slants goes, the growth factors should still be based on the step up ratio. The hard part is knowing how much yeast you start with. If you get say 1 ml of yeast from your slant, is that 1 billion cells? The general assumption that the spreadsheet is based on is that in 1 ml of concentrated yeast, there are 1 billion cells, Ie. in a 100 ml yeast pack, there are 100 billion cells. If the pack is only at 70 % viability then there is only 70 billion cells or 70 ml of yeast.

For more explanation, lets say that at the end of your first step (100 ml) you have 20 billion cells. This is treated as 20 ml of concentrated yeast. If you then step up to 200 ml, the step up ratio is not 2 (200/100) but actually 10 (200/20). It is not the volume of wort in the original starter that is used but the volume of yeast. Hopefully that makes sense.

Anyway, as discussed, the results agree with Mr Malty, and other calculators that I have seen so the method seems sound. However I am happy to be convinced otherwise. Lets keep the discussion going. If anything, we are increasing our understanding of yeast, which can only improve our beer.

Cheers

Tim

 

[Wolfy]

Anyway, the aim of the spreadsheet was not to determine the OG of wort additions (which it does anyway), but more how much yeast growth is achieved from a given starter size and pitching rate.

True, but if someone followed the instructions provided in the first post (most likely the results from the speadsheet), they'd be adding wort at a much higher gravity than required.

The main approach to this method is that I don't want to have to chill the starter and decant off the spent wort at the end of each step. Adding more wort to the same vessel to achieve the 1.040 minimises handling and also decreases risk of contamination. It also reduces the time from step 1 to final pitch. As stated in a previous post the alcohol that is produced may be detrimental, however, if the above is true, then not much alcohol is produced. However, if you are stepping up five times (without decanting) then the amount of alcohol contained towards the end may be worth worrying about.

Not decanting the wort at each step is the most logical and reasonable approach, however - as I suggested - if you assume that minimal fermentation has taken place in the 12-24 hour cell-growth window, then very little alcohol will have been produced and its impact on yeast growth will be far less significant than other things such as nutrient and oxygen availability.
It would actually be very easy to test, simply take gravity readings at each step (with a refractometer) of the starter process and record the changes.
Since any alcohol will be diluted 5 to 10 times by the next step of the start, I'd suggest that (as per details in How to Brew) stepping up the yeast into virtually identical wort each time is far more important, if you were to change the wort properties as suggested in your first post, the yeast would suffer great deal of shock - which is especially relevant because you are not letting it develop reserves to cope with such shock but rather pitching new wort into yeast that is still in the growth phase.

As far as your analogy of "highly concentrated super fed yeast from a smack pack", I disagree. If I put 1 smack pack into a litre starter (step up ratio of 10), I get 150 billion cells, or a growth rate of 1.5. Therefore, if I add my 20 ml into 200 ml, which is a step up rate of 10, I should also expect to get a growth rate of 1.5. As long as step up ratios are the same, each yeast cell will have the same amount of wort to use and grow.

The standard numbers quoted for yeast/volume in a new pack/vial of yeast is 100billion cells in 100ml of liquid (20billion cells in 20ml)
As TB suggested earlier, the standard cell density in a starter is usually estimated to be around 100million cells per ml (2billion cells in 20ml).
There cannot be much disagreement with these basic numbers since they are referenced and quoted numerous times.
As a consequence, when working with yeast directly from a new pack/vial, you MUST recognise that its 10 times more concentrated than what one would get if you grew it in a wort starter of the same volume.
Also of vital importance is the fact that if you do pitch more yeast it does NOT mean that you will end up with more than the 100million cells per ml, the yeast will simply consume all the nutrients and there will be less cell division, and the growth factor of the yeast does NOT work from a set multiplier.

An alternate way to look at it is to consider that pitching a new 100ml pack/vial of yeast into 1l is NOT giving a step up ratio of 10x, because the yeast in the pack has been force fed and super concentrated, so the step up ratio is actually only 1x. The step up ratio is based on the fact that the cell density will be the same before and after it's stepped up, this is true if the starter is made from a slant or if it stepped up from another starter grown in wort, the only consideration then is the change in volume. However, that is not true if the first step of the starter comes from a pack of concentrated yeast, in which case the number of viable yeast cells is more important than the volume they have been condensed in.

The White brothers have said quite clearly in several pod-casts that when pitching a full pack of yeast into a small volume of wort, that the yeast will consume the nutrients very quickly, you'll get little to no growth and that it may actually have an adverse effect on the yeast's viability. To obtain maximum yeast cell growth it must be supplied with an abundance of nutrients and oxygen (the gravity of the wort is less important) and that is not provided when a full pack is pitched into a small starter.

If you still disagree then the only other analogy I can think of is to consider a full volume starter when compared to just the yeast slurry. If you pitch the full volume (say 1l or 100billlion cells) of a starter the concentration is 10million cells per ml of the total volume. However if you decant 9/10 of the liquid that leaves the 100billion cells in only 100ml of yeast slurry, which is pretty much the same as what the yeast manufacturers do when shipping packs of yeast, why send 100billion cells in 1l when they can send the same in 100ml of super concentrated liquid.

As a result IF the spreadsheet is based on a fixed ratio of what happens when you pitch 1pack of yeast into 1l of wort, then the basic premise is wrong, especially considering that yeast growth is based on cell division and that is determined by many factors. Once again, (based on what the White brothers and others have said on various pod casts) the growth factor for yeast grown in wort is not a constant and depends on many factors, (from memory) it might be as low as 1x and it may be as high as 4x or more. If there are many cells they will not divide so often, but if there are few cells there will be more cell division and growth - once again this comes back to the initial concentration of yeast and the volume into which it is pitched as well as other conditions such as nutrients and oxygen availability. To further complicate things the more cell division there is the more stressed the yeast can become and the higher the risk of mutations, which is why most often a step up size of between 5 and 10 times is recommended when making starters, its seen as the best balance between food supply, cell division and yeast viability and health.

As far as stepping from slants goes, the growth factors should still be based on the step up ratio. The hard part is knowing how much yeast you start with. If you get say 1 ml of yeast from your slant, is that 1 billion cells? The general assumption that the spreadsheet is based on is that in 1 ml of concentrated yeast, there are 1 billion cells, Ie. in a 100 ml yeast pack, there are 100 billion cells. If the pack is only at 70 % viability then there is only 70 billion cells or 70 ml of yeast.

Not if you follow the conventional wisdom as explained in TB's approach.
Rather than applying a fixed ratio for cell growth, calculations can be based on the expected cell density in the starter (100million cells per ml), this acknowledges that the yeast's growth factor will change depending on the initial conditions, sometimes the growth factor will be low and other times higher - this is adjusted on the MrMalty calculator via the condition slider at the bottom (it directly adjusts the growth factor).
Assuming small initial first step sizes and viable yeast from the slant, you can simply apply the standard cell density so the number of yeast cells is easier to estimate than a random calculation based on a fixed growth rate and/or the viability of the yeast declining depending on its age.

In the past I've worked with pretty much the assumption, theory and steps that TB outlined above:

So to end up with basically a fresh smack pack/vials worth of cells you would go....

10ml from slant (1 bilion cells) - into 50ml starter (grows to 5billion cells) - into 250ml starter (grows to 25billion cells) - into 1L (grows to 100billion cells)

Where a spreadsheet like yours will be most useful is to take that standard cell density and apply appropriate adjustments based on wort concentration, nutrient and oxygen availability and starter volume, as per what MrMalty does, but at each step of the starter process.

 

[Thirsty Boy]

Yep, what wolfy said.

The Mr malty calculator is great, its what i use, but only when i get to the right volumes - In general its numbers are calculated from pitching whole wyeast or whitelabs packs - and their cell densities are through the roof. So by pitching a pack into a liter, you are basically pitching a zero times increase - just supplying more nutrients. Yes, you will get some growth, maybe 50-100% depending on whether you use a stirplate or not. And thats why the final cell counts end up so high at about 150-250 million cells per ml, because of the massive pitching rates. But its not the case generally, not even on the Mr Malty calculator - try pushing it so you pitch a full fresh pack into the biggest possible starter it will allow you to have without using more than one pack (about 23L for a simple stater, or 8.5 for a stirred starter) and you will see that the predicted number of cells is actually considerably lower than 100million cells per ml - so the very high finishing cell densities you get pitching a full pack into a small starter is the exception not the rule. Its not simply that stirplates or starters "generally" result in higher final cell densities.

Your 20ml splits dont supply such a massive initial numbers of cells, so they wont result in such high finishing cell densities. Its true that its probably a waste to pitch them into the "next sized up" increment as I suggested in my previous post, that would be a massive pitching rate, and would result in some growth.. But on a similar scale to a whole pack in a liter... Maybe a 50% increase - instead, throw your 20ml (a fifth of the initial 100billion cells, so 20billion - and equivalent to a cultured sample of 200ml) into a 1L starter (stirred) and you will end up with pretty close to 100million cells per ml in the final volume, or the same as a nice fresh smack pack. Or maybe onto a 2L starter and end up with a similar number of cells as pitching a full pack into a 1L starter... No intermediate steps required, just a higher growth rate.

And thats what i think is the simplest way to manage it - pitch at 10million cells per ml and get 100million - end up at a 1L volume with 100billion cells - then you can just work off Mr Malty with its accuracy at the volumes and pitching rates normally involved in homebrew starters.

My possibly mistaken reading of what i have discussed with people like Chris White, the guys from Wyeast & Jamil - is that in very small volumes, like the 10ml first step from a slant, the starting number of cells doesn't really matter so much. And that in the smaller "steps" at 10ml, 50ml & maybe even 100ml, whether you use a stirplate or not doesn't really make much difference - once you get up to more homebrew volumes, it starts to make a big difference and continues to do so right up to commercial brewery volumes (although they aren't using stirplates in those sorts of volumes)

I am not completely with wolfy about your increasing gravity additions, i tend to do something pretty similar. I start my starters out at a quite low gravity and i do assume that the starter ferments out completely... I know it probably doesn't and that the gravity creeps up as i step up - but i go 24hrs between steps partially for this reason and like you have no intention of chilling and decanting at each step. It becomes less important when you are stepping up in 10x increments anyway.. The starting gravity has less influence. So really you might only need to care if you want a really big cell count for a high gravity starter, and you need to do another high pitching rate step beyond a "whole pack" level of starter.

Like i said, i wasn't trying to make it complex, i was trying to make it simpler. 10 millon cells per ml in = 100million cells per ml out = the same as a smack pack or vial in a 1L volume and you just use Mr malty from there.

Sorry it turned into such a type fest.

TB

 

[Wolfy]

My possibly mistaken reading of what i have discussed with people like Chris White, the guys from Wyeast & Jamil - is that in very small volumes, like the 10ml first step from a slant, the starting number of cells doesn't really matter so much. And that in the smaller "steps" at 10ml, 50ml & maybe even 100ml, whether you use a stirplate or not doesn't really make much difference - once you get up to more homebrew volumes, it starts to make a big difference and continues to do so right up to commercial brewery volumes (although they aren't using stirplates in those sorts of volumes)

Rightly or wrongly I see those first few small steps being as much about quality and infection control than anything else. Since I don't have ideal sanitary laboratory conditions, the smaller steps help the yeast get established and out-compete any bugs that may otherwise cause contamination if pitched directly into a larger sample. In theory they should also keep the required growth factor at a reasonable number since I recall a suggestion that very large growth factors are not desirable.

 

[stux]

Now I'm all confused when before I wasn't

 

[diatonic]

Have you done any testing with this for big step-ups? I'm trying to get to ~700B cells from a single vial of WLP007. I have a fresh vial which should be ~100B cells. Not sure how to do the math on the first step.

I started with 500ml of 1.040, pithcing 90% viable yeast, which puts me at 162B cells.

Step 2 400ml of 1.078 wort gives me 291B cells

Step 3 400ml of 1.108 wort gives me 476B cells

Step 4 700ml of 1.096 wort gives me 756B cells

Theoretically, giving me the 756B cells in a 2L starter. Almost seems to good to be true. Have you tested these big ramps to see if you get close? Also, trying to do this over 4 days, 1 day for each step.

EDIT: My other thought was to decant after each step and add fresh 1.040 wort to eliminate the affects of alcohol on the yeast, but don't want to crash cool & decant after each step if it isn't necessary.

 

[Wolfy]

Have you done any testing with this for big step-ups? I'm trying to get to ~700B cells from a single vial of WLP007. I have a fresh vial which should be ~100B cells. Not sure how to do the math on the first step.

I started with 500ml of 1.040, pithcing 90% viable yeast, which puts me at 162B cells.

Step 2 400ml of 1.078 wort gives me 291B cells

Step 3 400ml of 1.108 wort gives me 476B cells

Step 4 700ml of 1.096 wort gives me 756B cells

Theoretically, giving me the 756B cells in a 2L starter. Almost seems to good to be true. Have you tested these big ramps to see if you get close? Also, trying to do this over 4 days, 1 day for each step.

The MrMalty calculator is designed for the first step, much research has been put into that, so just use the numbers there.

Other than that the rest of your calculations, assumptions and theory appear to be vastly incorrect, it IS "too good to be true".
If you want ~700 billion cells, you will need (in a non commercial home-brew type situation) ~7L of starter wort, your 2L starter and multiple steps may result in only a few more cells than in the original pack and they may well be in worse condition than you started, since each small step size may not be providing enough nutrients.

When you pitch increasingly larger quantities of yeast into small volume starters, they consume all the nutrients very quickly and do not grow at all (reference table on page 140 "Yeast" book)
In addition if you listen to the BN podcasts featuring Chris White, he says quite clearly that pitching 1 new pack of yeast into small starter (500ml in your case) will result in little to no growth, so (from what I have read, listened to and understood) there appears to be little basis for any of the growth factors or assumptions that you have made above.