# Stepped Yeast Starter Calculator



## puffer555 (23/2/11)

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.


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## puffer555 (23/2/11)

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

Regards
Tim


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## felten (23/2/11)

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)


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## stux (23/2/11)

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


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## puffer555 (23/2/11)

Felten said:


> 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. 



Stux said:


> 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.


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## Wolfy (23/2/11)

puffer555 said:


> 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.


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## puffer555 (23/2/11)

Wolfy said:


> 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.


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## Thirsty Boy (23/2/11)

Wolfy said:


> 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


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## outbreak (23/2/11)

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


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## puffer555 (24/2/11)

Thirsty Boy said:


> 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.
> 
> ...



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


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## Wolfy (24/2/11)

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.


puffer555 said:


> *Step 2:*
> 
> Wort Addition 150 ml
> 
> ...



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.


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## Wolfy (24/2/11)

puffer555 said:


> 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).
> 
> ...


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.


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## felten (24/2/11)

Wolfy said:


> 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.


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## puffer555 (24/2/11)

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


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## Wolfy (24/2/11)

puffer555 said:


> 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.


puffer555 said:


> 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.


puffer555 said:


> 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.


puffer555 said:


> 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:


Thirsty Boy said:


> 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.


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## Thirsty Boy (24/2/11)

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


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## Wolfy (24/2/11)

Thirsty Boy said:


> 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.


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## stux (24/2/11)

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


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## diatonic (20/4/11)

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.


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## Wolfy (20/4/11)

diatonic said:


> 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.
> 
> ...


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.


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## haysie (20/4/11)

Wolfy said:


> 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.



I`ve always been a tad unconvinced re. the 6x and 10x that seems to be talked about a lot, i.e 1 pack of yeast x 6 = 600 ml starter.
Today I split a fresh pack of Wyeast1056 at approx 1pm, I didnt split the nutrient pack so the volume is about 90ml of yeast liquid. I took 4 x 15ml vials from the pack and added the remaining 30 ml to a fresh 1ltr starter (so thats about 35x). Just got in the door and the starter having been spinning the last 3 hrs is going off, huge krausen.


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## BjornJ (20/4/11)

Hi guys,
I hope this is not too off-topic as it leads towards the same goal : pitching enough yeast.

Rather than doing massive starters for lagers, would "douple dropping" do a similar kind of thing?

Thinking something along the lines of:
Stir plate starter of say 2 litres from Whitelabs vial.
Pitch entire 2L starter into 23 litres of wort at 15 degrees.
Next morning (say 10-15 hours later), splash wort from tap into another fermenter to add more oxygen.
Set temp to 11 degrees and leave to ferment.

Would the "double dropping" of aerating the wort by transferring it to another fermenter help to ensure enough yeast?

(and hopefully not create diacetyl) 


After making several lagers and stir plate starters I don't think I am pitching enough yeast.
Thinking of if trying again maybe the double drop technique would help the yeast grow bigger.



thanks
Bjorn


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## Wolfy (20/4/11)

haysie said:


> I`ve always been a tad unconvinced re. the 6x and 10x that seems to be talked about a lot, i.e 1 pack of yeast x 6 = 600 ml starter.
> Today I split a fresh pack of Wyeast1056 at approx 1pm, I didnt split the nutrient pack so the volume is about 90ml of yeast liquid. I took 4 x 15ml vials from the pack and added the remaining 30 ml to a fresh 1ltr starter (so thats about 35x). Just got in the door and the starter having been spinning the last 3 hrs is going off, huge krausen.


That's because you are right ... but you're just looking at it the wrong way. 

The "100million cells per ml" that TB is talking about on the previous page is the estimate for the density of yeast in a normal concentration of _starter_.
A Wyeast pack is super-concentrated highly viable yeast, 30ml of concentrated-yeast from that pack should have about 30billion cells, which is the equivalent of a 300ml starter.
Hence, by pitching 30ml of a Wyeast pack into 1L starter the step-up ratio is about 4x not 35x.
If you were to pitch 20ml of fresh-pack yeast into a 1L starter, you'd be stepping up about 5x (to 10x depending on age of the pack) which is close to the ideal step size.


BjornJ said:


> Rather than doing massive starters for lagers, would "douple dropping" do a similar kind of thing?


Yes ... there is some historical information that German brewers used to do something very similar, although they had a different name for it, I think there is a link from *BribieG*'s thread, either here or on JBK.


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## Thirsty Boy (20/4/11)

I think that what you arethinking of is Drauflassen. Or double batching. Not the same thing as double dropping from teh English brewing tradition.

Its about pitching your yeast to a portion of your wort, then later adding some more wort in one or more steps just before the yeast gets to fully active fermentation.

Something thats really very easy for a no-chill brewer to do, one cube - pitch - wait 12 hrs or so - pitch next cube. Similar effect in alot of ways to double dropping in that it adds oxygen, but its also kind of like a supersized starter and keeps the yeast in lag phase for longer because it kind of "tricks" them into thinking they are in a differeent environment to the one they are really in.

But don't be tricked into thinking that you now get to pitch just a single pack into your double batch of bock. It still works out that you really want to add 2/3rds of the proper amount of yeast for the whole wort amount (OK, maybe you will get away with half) so it can be handy if your calculations tell you that you need 7L of starter and you only have a 5L flask.... But it isn't knocking something like a 7L starter down to being able to do it in a 2L flask or anything quite qs dramatic as that.

I'm afraid that if you want to make lagers, and you want to pitch at the recommended rates, you just have to pony up for a big arsed vessel to do it in, or re-pitch yeast from a previous batch.

Braukaiser has a nice article on it ( http://www.braukaiser.com/wiki/index.php?title=Drauflassen ) although when he is trying to give you a way to manage the process at a HB level he has it harder than we enlightened folks, because he cant use No-Chill to help him make it easy.


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## felten (20/4/11)

Pick a bunch of styles that fit the yeast you want to use, and brew them in a progression with re-pitched yeast like TB said.

I'm stuck with a 2L flask as well, and that's the way I would go about it. Even then it's still a PITA because a small starting lager will still require a large (~3L) starter.


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## BjornJ (21/4/11)

thanks, read the Drauflassen article now.
Maybe that's what I can try next.

thanks
Bjorn


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## stux (20/5/11)

Based on what TB said about yeast growth, I've whipped up this simple spreadsheet.

View attachment Yeast_Stepping_Calculator.xlsx



The idea is that yeast in a starter will only grow to a certain density. 

For example, 100Mcells/mL if you only allow 12-18 hrs of growth, but if you were to allow the yeast to fully ferment then you might expect 150Mcells/mL

This spreadsheet assumes a fixed maximum growth density (which can be changed) and then iterates step sizes assuming a certain growth factor.

I split my WYeast activator packs 4 ways to end up with 30mL vials with the same cell density as the original package.

So for example, 

to obtain circa 525 Billion yeast cells (to pitch 55L of 1.052 Ale) you might start with 30mL of 56% viable WYeast, and then apply a growth factor of 6.25x

which at 100Mcells/mL starter density limit would mean I should pitch my 30mL vial into 840mL of wort, that'd then grow to 100Mcells/mL which is also a 6.25x growth factor, which I would then pitch into 5,250mL for a total of 525 Billion cells after 2 steps.

That's assuming 100Mcells/mL

If I were to assume 150 then the steps would be 560 and 3,500mL, respectively.

Of course, since we're assuming a fixed density the interim steps don't really matter that much, and in fact I could use 500 and then 3500, or whatever.

The other interesting thing is, once you have worked out your growth factor to use to get your final yeast count, then the maximum growth density just reduces the amount of wort required in your starters...

Now, the problems?

I'm assuming a certain maximum density. This does not correlate well with Mr Malty, but if you use 78 for the Growth Max Density, then it does correlate with a stirred starter from a single vial.

Also, I'm not calculating the differential step size, only the pure final volume, assuming 1.040.

Thoughts?


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## matho (20/5/11)

Have you also tried playing around with This

Cheers matho


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## Wolfy (20/5/11)

Stux said:


> Thoughts?


Firstly, I can't actually look at the spreadsheet since it seems I use an antiquated version of Office, so my comments are based only on what you said above.

When using stepped-yeast-starters, the MrMalty calculator becomes less and less useful, since the calculator is designed ONLY to work when inoculating a single step-starter with a pack of liquid yeast, and since that nearly always means you are pitching at a very high inoculation rate, the results are not always applicable to stepped starters.
The Wyeast calculator does allow for fractions of packets to be used, so you might find that more useful, if it correctly adjusts for the 1/4 pack that you use for your initial pitch, so its worth testing your numbers against that.

However, from memory it is usual to expect yeast cells to spit maybe 2 or 3 times, this is usually called the 'growth factor' and if you are using more than 6x for the same thing it may be a little unrealistic.

While I'd suggest that the previously mentioned '100million per ml' is a good maximum cell density to base calculations on, it also makes it so simple to work out the required starter size, that one could not possibly need a spread sheet for it. 525 billion cells = 5.25L it's a no-brainier, so your spreadsheet must do more than that. 

It also seems that you have not taken into account the Inoculation Rate, but even then based on info on page 140 of the 'Yeast' book, when using an inoculation rate of anywhere between 25 and 125 million cells/ml you'll get much the same Yield factor (growth rate). However since there is a huge spread between those numbers, it mostly indicates that pretty-much-anything will work, especially keeping in mind that the 'industry standard' step size is 10x the previous volume.

Having said all that, you know the number of cells in your split-pack (adjust the usual 100billion total number of cells in the pack against manufacture date as per the MrMalty calculations) and you know the final volume (based on the maximum cell density of 100million per ml), so then all you need to do is apply an inoculation rate of anywhere between 25 and 125 million cells/ml. Interestingly, I'd guess that those numbers work out that mostly any resonable starter/step size will work, and only 1 step is required between the 1/4 of a pack and the total volume required.


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## stux (20/5/11)

Wolfy said:


> Firstly, I can't actually look at the spreadsheet since it seems I use an antiquated version of Office, so my comments are based only on what you said above.



Excel 2004 Version

View attachment Yeast_Stepping_Calculator.xls




> When using stepped-yeast-starters, the MrMalty calculator becomes less and less useful, since the calculator is designed ONLY to work when inoculating a single step-starter with a pack of liquid yeast, and since that nearly always means you are pitching at a very high inoculation rate, the results are not always applicable to stepped starters.
> The Wyeast calculator does allow for fractions of packets to be used, so you might find that more useful, if it correctly adjusts for the 1/4 pack that you use for your initial pitch, so its worth testing your numbers against that.
> 
> However, from memory it is usual to expect yeast cells to spit maybe 2 or 3 times, this is usually called the 'growth factor' and if you are using more than 6x for the same thing it may be a little unrealistic.



I think the issue is what I have called "Growth Factor" is actually step size

If you're doing step sizes of 10 fold, and you're always ending up with 100million/mL, then you have total growthof 9 fold, which I guess means the yeast split 2 and bit times? And that "2 and a bit" is that the true growth factor?



> While I'd suggest that the previously mentioned '100million per ml' is a good maximum cell density to base calculations on, it also makes it so simple to work out the required starter size, that one could not possibly need a spread sheet for it. 525 billion cells = 5.25L it's a no-brainier, so your spreadsheet must do more than that.



Yes, it splits the steps based on a maximum step size



> It also seems that you have not taken into account the Inoculation Rate, but even then based on info on page 140 of the 'Yeast' book, when using an inoculation rate of anywhere between 25 and 125 million cells/ml you'll get much the same Yield factor (growth rate). However since there is a huge spread between those numbers, it mostly indicates that pretty-much-anything will work, especially keeping in mind that the 'industry standard' step size is 10x the previous volume.



Exactly, assuming we reach maximum cell density, then the innoculation rate doesn't matter so much, what I'm trying to do is have the innoculation rate be the same for each step to minimize cell growth required at each step, before fresh wort is added



> Having said all that, you know the number of cells in your split-pack (adjust the usual 100billion total number of cells in the pack against manufacture date as per the MrMalty calculations) and you know the final volume (based on the maximum cell density of 100million per ml), so then all you need to do is apply an inoculation rate of anywhere between 25 and 125 million cells/ml. Interestingly, I'd guess that those numbers work out that mostly any resonable starter/step size will work, and only 1 step is required between the 1/4 of a pack and the total volume required.



Exactly

It is interesting to play with the step size and maximum cell density, the step size basically gets you to a certain number of cells after a certain number of steps, and the max density changes the amount of starter you need for those cells...


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## matho (20/5/11)

Hey wolfy the wyeast calculator does let you use fractions of the pack just put 0.25 in the no. of packets box 

Cheers


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## stux (20/5/11)

matho said:


> Hey wolfy the wyeast calculator does let you use fractions of the pack just put 0.25 in the no. of packets box
> 
> Cheers



I actually tried using "Propogator" which is a 30 ml packet and then "0.56" for the quantity which then becomes the viability


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## matho (20/5/11)

Don't worry about me I'm not reading very well tonight wolfy said does and I read doesn't


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## matho (20/5/11)

i actually plotted some numbers off the wyeast calculator onto a spreadsheet 

View attachment yeast.xls


this was done on open office and save as an xls if the graphs dont come up here is what they look like





as you can see the growth rate varies a bit in the calculator

cheers


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## Wolfy (21/5/11)

matho said:


> Hey wolfy the wyeast calculator does let you use fractions of the pack just put 0.25 in the no. of packets box


Yeah the calculator lets you put numbers in, I was more questioning its accuracy, especially at lower pitching rates, since I presume it was designed to be accurate for full or even multiple packs and higher pitching rates.


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## Wolfy (5/8/11)

I know this is an old thread, but a post I just made on the UK JBK forums made me realize how easy it is to work out.

*Based on the assumptions mentioned by TB on the previous page - it should all come down to a few easy steps:*

Work out how much yeast you need to pitch (_1 million cells of viable yeast, for every milliliter of wort, for every degree plato, adjusted for the type of beer you are brewing (or just use MrMalty it does this for you)_)
Assume a maximum cell density to determine the required starter volume size (_100million cells per ml, 100billion per L as per TB's info on previous page_).
Determine your starter pitching rate (_10milion cells per ml pitching rate, as per TB's info on previous page_)
Step that starter size 'down' by a factor of between 5 and 10, progressively until you get to the number of yeast cells you assume you are starting with
Adjust the step sizes and starter volumes to make them more even/logical
*Example:* Brewing 40L of Ale at 1.045, starting from 1billion cells (_an older split yeast pack or a 10ml starter from a slant_).

We need 336 billion yeast cells (_apply calculation or use MrMalty_)
That equates to 3.4L starter
Step that starter down by 10x is a 340ml starter (_into which we need to pitch 3.4billion cells, our 1billion is not yet enough so step again_)
Step that down by 10x to 34ml (_we need to pitch 0.34billion cells so we are at/below our starting target of 1billion cells_)
Now to even the step sizes and make the starter volumes more sensible:

Start with 1billion cells from 10ml slant-starter or old split yeast pack
Step up by 7x into 70ml starter (_~7billion cells_)
Step up by 7x into 500ml starter (_~50billion cells_)
Step up by 7x into 3.4L starter (= our required 340billion cells)
The process is quick and easy, however I have no idea how to put that kind of logic into a spreadsheet, especially when step sizes anywhere between 4x and 10x are equally valid and one step might be 5x and the next could be 10x and it would still work fine.


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## stux (5/8/11)

This is how my spreadsheet works

Except it doesn't iterate. But you enter 7x, you get your 7 fold result


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## Wolfy (5/8/11)

Stux said:


> This is how my spreadsheet works
> 
> Except it doesn't iterate. But you enter 7x, you get your 7 fold result


Yeah, I used a table to show the various step multipliers that I can then manually lookup to find the result, works for me, but it needs to be automated before it is user-friendly.


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## dustinsullivan (27/10/11)

A very good idea. Here is my take on the whole thing YeastCalc


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## stux (27/10/11)

sulli_42 said:


> A very good idea. Here is my take on the whole thing YeastCalc



Neat

Can you add an option to use L for batch size?


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## Amber Fluid (28/10/11)

Strange how everything is in ml and liters but the batch volumes are in US Gallons. :blink:


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## stux (28/10/11)

Amber Fluid said:


> Strange how everything is in ml and liters but the batch volumes are in US Gallons. :blink:



In the US, Yeast starters are often done in metric 

I assume this is the yeast scientists doing


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## dustinsullivan (29/10/11)

Stux said:


> In the US, Yeast starters are often done in metric
> 
> I assume this is the yeast scientists doing



Americans are a little confused when it comes to measuring things. 
I love the metric system, very easy to use. Unfortunately I grew up using U.S. system, I have a hard time visualizing the metric system, but I'm getting better. Homebrewing has helped a lot in that area. I am working on putting a menu in to change the volume units to metric. Thanks for the input.


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## [email protected] (29/10/11)

sulli_42 said:


> A very good idea. Here is my take on the whole thing YeastCalc



I have to agree with stux, this is very neat! Bookmarked! 

Seems to use the same calculations on inoculation rates producing X amount of cell growth as i had been doing from the charts out of the yeast book.
I still make initial assumptions on my small amounts of saved yeast cell count with Mrmalty.

Its so handy i dont mind having to convert the gallons


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## dustinsullivan (29/10/11)

Beer4U said:


> I have to agree with stux, this is very neat! Bookmarked!
> 
> Seems to use the same calculations on inoculation rates producing X amount of cell growth as i had been doing from the charts out of the yeast book.
> I still make initial assumptions on my small amounts of saved yeast cell count with Mrmalty.
> ...



I added a conversion menu today, just for you aussies  . It looks a little clunky, but maybe I can refine it some. And you are correct, it is based on the same data. I plotted the data on page 140 of White's 'Yeast" book, in excel and came up with a nice exponential curve that seemed to fit Mr.Malty's growth rate as well.


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## Amber Fluid (29/10/11)

Good work Sulli. Thanks


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## stux (29/10/11)

What was the source for the yeast viability vs age?


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## dustinsullivan (30/10/11)

Chris White


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## dustinsullivan (3/11/11)

Hello Gents,

I put together some charts showing how I got at the formulas that I'm using in my calculator, thought it might be of interest to some of you. Anyway, check it out, and let me hear your thoughts. 

Growth Charts


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## stux (3/11/11)

I enjoyed your growth charts 

The problem with the viability is if you enter June 3rd, 2011, then it spits out 0% viability. Mr Malty spits out 10% viability, and BeerSmith2 spits out 28.85%

Vast difference 

Looking at my 4month old vials, I can certainly say that they are better than 0%

And I don't think there is a way for me to override the viability :-\

Might be worthwhile doing a similar curve analysis against the Mr Malty calculator, as I think its numbers are fairly good...

PS: I haven't read "Yeast", its on my Christmas wishlist


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## stux (3/11/11)

Stux said:


> I enjoyed your growth charts
> 
> The problem with the viability is if you enter June 3rd, 2011, then it spits out 0% viability. Mr Malty spits out 10% viability, and BeerSmith2 spits out 28.85%
> 
> ...



More so, Although White Labs say that the Shelf Life for their yeast is 4 months, that is not the same as the viability, rather its based on a retail realities of expectations of minimum viability 

"
The shelf life for White Labs Yeast is four months. *Yeast used after this point is usually fine*, but lag times will be longer. There will be *living yeast in most vials for 6-12 months*, so if a starter is made to activate the yeast, successful fermentations can be carried out with aged yeast.
"

So, I would guess that at a minimum viability should be >0 for 6-12 month old yeast

From my quick checks Mr Malty uses 1% for >365 days and 10% for >4 months


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## [email protected] (3/11/11)

Stux said:


> I enjoyed your growth charts
> 
> The problem with the viability is if you enter June 3rd, 2011, then it spits out 0% viability. Mr Malty spits out 10% viability, and BeerSmith2 spits out 28.85%
> 
> ...



I had the same viability issue.

I just punched in what ever date made it say the viability i get from Mr malty, then use the calculator as normal.


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## dustinsullivan (4/11/11)

I agree the viability seems a little on the high side. I personal have made starters from really old yeast and they fermented out just fine, I think viability is a pretty generic number and is very hard to pin down due to so many variables on handling and storage. my calculator uses 0.6% viability lost per day, and I thought that's what mr. malty used as well, I'll be looking into this some more. it would be very easy to lower it. But one way around it is to set the date to anytime in the future, the viability then goes to 100% and you can just manually enter a cell count to correlate with whatever viability you want.


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## dustinsullivan (4/11/11)

Okay, I made some adjustments. Turned out to be easier than I thought. Give it a try now, it should be pretty close to mr. malty's calculations for viability.


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## stux (4/11/11)

Cool

Viable Cell Count seems to be ignoring Initial Cell Count when its in the 10% viable range

So, if you are at 84% viability, then modifying initial cell count seems to work as expected, but if its in the 10%, then it seems to assume 100billion Initial Cells and ignores the Initial Cell Count (which could be 50 or 25 billion for example)

The red/green cell counts is a nice touch 

PS: this is about to become my go-to yeast starter calculator


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## Hogan (4/11/11)

Nice job Sulli. I like it.

Cheers, Hoges.


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## dustinsullivan (4/11/11)

Stux said:


> <br />Cool<br /><br />Viable Cell Count seems to be ignoring Initial Cell Count when its in the 10% viable range<br /><br />So, if you are at 84% viability, then modifying initial cell count seems to work as expected, but if its in the 10%, then it seems to assume 100billion Initial Cells and ignores the Initial Cell Count (which could be 50 or 25 billion for example)<br /><br />The red/green cell counts is a nice touch <img src="http://www.aussiehomebrewer.com/forum/style_emoticons/default/smile.gif" style="vertical-align:middle" emoid="" border="0" alt="smile.gif" /><br /><br />PS: this is about to become my go-to yeast starter calculator <img src="http://www.aussiehomebrewer.com/forum/style_emoticons/default/wink.gif" style="vertical-align:middle" emoid="" border="0" alt="wink.gif" /><br />


<br /><br /><br />

Ah, I see. I'll have to go back in and fix that, good catch. I'm glad you find it useful, I hope other people will as well.


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## dustinsullivan (4/11/11)

Okay, I think I've got it. Give it a go now. I really appreciate you blokes giving me some productive feedback on this thing, I've posted it on several different brewing forums, and you guys are the only ones who have been helpful in working out the bugs. Thank You.


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## Yob (4/11/11)

Stux said:


> can you add an option to use L for batch size?




you didnt look too hard unless it was just done...


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## [email protected] (4/11/11)

iamozziyob said:


> you didnt look too hard unless it was just done...  yes mate he made the addition earlier just for us aussies
> 
> View attachment 49793






sulli_42 said:


> Americans are a little confused when it comes to measuring things.
> I love the metric system, very easy to use. Unfortunately I grew up using U.S. system, I have a hard time visualizing the metric system, but I'm getting better. Homebrewing has helped a lot in that area. I am working on putting a menu in to change the volume units to metric. Thanks for the input.






sulli_42 said:


> I added a conversion menu today, just for you aussies  . It looks a little clunky, but maybe I can refine it some. And you are correct, it is based on the same data. I plotted the data on page 140 of White's 'Yeast" book, in excel and came up with a nice exponential curve that seemed to fit Mr.Malty's growth rate as well.


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## stux (4/11/11)

sulli_42 said:


> Okay, I think I've got it. Give it a go now. I really appreciate you blokes giving me some productive feedback on this thing, I've posted it on several different brewing forums, and you guys are the only ones who have been helpful in working out the bugs. Thank You.



Welcome 

Its good to have someone responsive to feedback 

I think the tab order could use a bit of improvement too

I think it should go from the Top left cell across and down

at the moment it goes from the yeast cells, back up to the top, then back down to the steps... which I think could be on purpose... but I keep on clicking in the batch size, and then tabbing and it skips straight to the steps over the yeast, which is not what I expect


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## Brad Churchill (4/11/11)

That is one brilliant calculator Sulli. 
Well done and thanks!!

Cheers Brad


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## dustinsullivan (4/11/11)

To be perfectly honest, I haven't even set the tab order. I hadn't tried tabbing through the application till now. I see what your saying; the order doesn't make any sense. It definitely needs to go from top left across and down, that makes the most sense to me as well. I'll work on it tonight. Thanks again.


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## dustinsullivan (5/11/11)

Got it. Nice suggestion Stux. That's much better.


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## stux (18/2/12)

Heya sulli,

I noticed that you've now registered the domain http://www.yeastcalc.com, nice

Also, you don't have a contact/suggestions link that I can see 

Perhaps put a link to a thread on this forum 

Anyway, I have a suggestion

I would like to see the multiplication factors between steps, 

So, for example, I'm stepping up from 9.75B cells to 40B, I'd like to see the growth factor of x4.1

I figured a good place would be to just put some text next to the result field for each step


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## dustinsullivan (21/2/12)

Stux said:


> Heya sulli,
> 
> I noticed that you've now registered the domain http://www.yeastcalc.com, nice
> 
> ...



Hello Stux,

Yes, I have been wanting to put a Feedback/Contact link up for awhile, it is done now. :beerbang: 

Not sure about the growth factor though, how useful is this information really? I also think it could create a slew of questions from less knowledgeable users.


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## cdbrown (21/2/12)

sulli,

excellent site, am now basing my starters and steps on your info. A potential improvement is to state clearly on the site to try and get the 50-100 target innoculation rate. It's not mentioned on the care and feeding page even though it states the innoculation rate is important, and unless you hover over innoculation cell the user wouldn't really know if the rate is right. Is it possible to have the colour change when outside the target just like the total finished cells is red when it's below target.

Also what is the impact of say stepping up a starter where the first step innoculation is only 17M/ml compared to trying for 50M/ml?

Cheers
-cdbrown


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## stux (21/2/12)

sulli_42 said:


> Hello Stux,
> 
> Yes, I have been wanting to put a Feedback/Contact link up for awhile, it is done now. :beerbang:
> 
> Not sure about the growth factor though, how useful is this information really? I also think it could create a slew of questions from less knowledgeable users.



I try to keep my steps between 4-5x increase

Being able to see the increase as a multiple makes it easier for me to keep my steps even, generally favouring large steps early on rather than later


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## cdbrown (21/2/12)

Stux said:


> I try to keep my steps between 4-5x increase
> 
> Being able to see the increase as a multiple makes it easier for me to keep my steps even, generally favouring large steps early on rather than later



Do you find that in order to get the 4-5x increase in the first step or so your innoculation rate is about 15-20M/ml? An example is a lager yeast from November last year = 27B viable cells. 1.5L starter on stir plate produces 135B cells with an innoc rate of 18M/ml. Targeting a 50 innoc rate, the starter would be 0.5L and the outcome 82B viable cells (x3 growth).


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## hando (21/2/12)

Is this going to be airlocked?

Well done - it's a great calculator!


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## stux (21/2/12)

cdbrown said:


> Do you find that in order to get the 4-5x increase in the first step or so your innoculation rate is about 15-20M/ml? An example is a lager yeast from November last year = 27B viable cells. 1.5L starter on stir plate produces 135B cells with an innoc rate of 18M/ml. Targeting a 50 innoc rate, the starter would be 0.5L and the outcome 82B viable cells (x3 growth).



I find the biggest factor is actually time. If there are enough nutrients and constant O2, then the yeast will continue growing until they use up the nutrients, or reach a certain density.

That's been my experience anyway, but this means spending 36-48 hours on a step

BUT its not like I'm pulling out a microscope and counting cells 

I tend to do 2 or 3 step starters over a period of week because I'm starting from generally very old 1/4 packets of wyeast. From readings I've done, the advice is to do the bigger steps first

http://www.maltosefalcons.com/tech/yeast-p...s-and-practices


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## stux (21/2/12)

Example of a yeast step i just did this morning


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## dustinsullivan (21/2/12)

cdbrown said:


> sulli,
> 
> excellent site, am now basing my starters and steps on your info. A potential improvement is to state clearly on the site to try and get the 50-100 target innoculation rate. It's not mentioned on the care and feeding page even though it states the innoculation rate is important, and unless you hover over innoculation cell the user wouldn't really know if the rate is right. Is it possible to have the colour change when outside the target just like the total finished cells is red when it's below target.
> 
> ...



The 50-100 million cells/ml target inoculation rate is based off of data from Chris White's book "Yeast". It appears to be the most effective inoculation rate for optimizing the health and growth rate of the yeast. 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. As the inoculation rate decreases the growth rate increases, this places more and more stress upon the individual yeast cells as the number of divisions per cell increases. So, in other words, you will get the most bang for your buck in the 50-100 million cells/ml range, but decreasing or increasing the inoculation rate will still produce yeast cells capable of doing their job.


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## Wolfy (21/2/12)

Stux said:


> BUT its not like I'm pulling out a microscope and counting cells


I have two microscopes, but to be totally honest have never yet bothered to use them for counting yeast.
However, if you don't count cells and test your formula and theories how do you know that the information you have published is correct?


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## stux (21/2/12)

Wolfy said:


> I have two microscopes, but to be totally honest have never yet bothered to use them for counting yeast.
> However, if you don't count cells and test your formula and theories how do you know that the information you have published is correct?



Yeast slurry volumes


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## TSMill (21/2/12)

cdbrown said:


> Do you find that in order to get the 4-5x increase in the first step or so your innoculation rate is about 15-20M/ml? An example is a lager yeast from November last year = 27B viable cells. 1.5L starter on stir plate produces 135B cells with an innoc rate of 18M/ml. Targeting a 50 innoc rate, the starter would be 0.5L and the outcome 82B viable cells (x3 growth).


The 50-100 gives you the best hang for your buck, all else being equal. yes in that example the 1.5L starter results in a higher yield, but a 0.5L starter followed by a 1L starter gives you more cells (206) for the same 1.5L total word used.


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## stux (22/2/12)

sulli_42 said:


> Alright Stux, because I like you, and because I'm curious to see what kind of reactions I get.  I'm calling it "doublings" because thats what it is, but it is the same as growth rate.
> 
> Just so you know, this might be coming back down if I get too many noob questions about what it is and why it is there.



Still getting version 2.15 at the moment


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## dustinsullivan (22/2/12)

Stux said:


> Still getting version 2.15 at the moment


 Try refreshing your browser.


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## dustinsullivan (22/2/12)

Nevermind, I can't get it up on my laptop either, it must not have posted to the server correctly. I'm in class right now, but I'll try to get it working when I get home in a few hours.


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## [email protected] (22/2/12)

sulli_42 said:


> The new version is online now, but I've been thinking about this growth rate number today, and I don't think it is such a good idea. I think it is going to confuse people. If you make a 1.5 liter starter with 100 billion cells on a stir plate you get a growth rate of 1.76, but if you make a 3 liter starter with 100 billion cells on a stir plate you get a growth rate of 2.8; obviously a 2.8 growth rate is better than 1.76 growth rate, in fact the bigger I make my starter the bigger the growth rate becomes, and we all know that bigger is better right?
> Wrong. Bigger is not better; bigger starters put more stress on the yeast, resulting in less healthy yeast cells.
> Joe brewer is going to be confused by this seeming paradox, which makes the growth rate number meaningless.
> The number you should be looking at is the inoculation rate.



Can you make the inoculation rate number go red/green if it falls outside/inside the recommended range? 
Like the pitch rate and finished cell count.


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## [email protected] (23/2/12)

sulli_42 said:


> Done. This was a good suggestion, I think it helps to clarify things a bit. I also changed the "growth rate" label back to "number of doublings". I think these two changes will help prevent confusion. Thanks.
> 
> I also bumped the maximum inoculation rate up to 249 million cells/ml, this is literally the highest number the calcs can go to, once the inoculation rate surpasses 249 it actually calculates a _negative_ number of new cells produced.
> 
> Once again my thanks goes out to the AussieHombrewers, you guys ROCK! :super:



Very Nice work sulli, you have created a very useful tool for home brewers to make better beer!


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## mckenry (23/2/12)

This seems pretty good.

I have been playing around with it. Still trying to decide if minimum steps, whilst keeping the innoc rate between 50-100 is the way to go, or evening out step volumes...

One thing though. From the Wyeast webpage, they state 100B cells is enough to innoc 5 gallons. Assuming 100% viability. and OG between 1.034 & 1.060

When I have 100% viability in the calc and 5 gallons at 1.034 - the calc says its underpitching by 21B cells (21%) or at a rate of 1.1mill cells/mL. 21% is enough to think about.

This is without a starter as the wyeast page states its enough to go directly into 5 gallons.

Comments?


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## [email protected] (23/2/12)

mckenry said:


> This seems pretty good.
> 
> I have been playing around with it. Still trying to decide if minimum steps, whilst keeping the innoc rate between 50-100 is the way to go, or evening out step volumes...
> 
> ...



This calculator uses pitching rates same as MR malty calculator / info from Yeast book / Mr white ect.

Wyeast also recommend pitching slightly warmer than your desired ferment temp, which encourages yeast growth and you can subsequently get away with the large SG range they say the packs will inoculate.

For me i certainty would not be treating a 1034 wort the same as 1060.


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## stux (23/2/12)

End of the day, its in WYeast's best interests to imply you don't need a starter.

Its very hard to get 100% viable Wyeast in australia anyway


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## mckenry (23/2/12)

Beer4U said:


> Wyeast also recommend pitching slightly warmer than your desired ferment temp, which encourages yeast growth and you can subsequently get away with the large SG range they say the packs will inoculate
> 
> For me i certainty would not be treating a 1034 wort the same as 1060.



Oh yeah, for sure. Just wondering why this calc says a new wyeast pouch at 100% viability was a 21% underpitch at OG 1.034
Would only be worse the higher the OG goes.

But as you say, pitching warmer...

I have always just split new packs and built starters anyway, using MrMalty.

Seeing as I can have a pretty good guess at 33.3B cells (1 pack split 3 ways) now I can adjust my steps better.
Question for slurry scavengers. How do you estimate your starting cell count?


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## dustinsullivan (23/2/12)

mckenry said:


> Oh yeah, for sure. Just wondering why this calc says a new wyeast pouch at 100% viability was a 21% underpitch at OG 1.034
> Would only be worse the higher the OG goes.
> 
> But as you say, pitching warmer...
> ...



Lot of guys are using mr malty to estimate cell counts from slurry, and then using this number for initial cell count input for yeastcalc


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## cdbrown (23/2/12)

it would seem that Total Cells at Finish is always green even if the cell count is below the target for the batch. Was working prior to the colour change on the innoculation rate.


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## dustinsullivan (23/2/12)

cdbrown said:


> it would seem that Total Cells at Finish is always green even if the cell count is below the target for the batch. Was working prior to the colour change on the innoculation rate.



Ugh.


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## dustinsullivan (23/2/12)

I learned something tonight, logic problems and homebrews do not mix well. 
Even so, I think I've got it working properly now. Please let me know if there are any more bugs, I'm going to pour myself another pint :beer:


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## MaltyHops (23/2/12)

mckenry said:


> ...
> Question for slurry scavengers. How do you estimate your starting cell count?


_THIS_ post might apply to your question.


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## TSMill (24/2/12)

sulli_42 said:


> I learned something tonight, logic problems and homebrews do not mix well.
> Even so, I think I've got it working properly now. Please let me know if there are any more bugs, I'm going to pour myself another pint :beer:


For 100% viability in the calc I need to obtain yeast 5 days into the future, which in practice I find hard to achieve.


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## dustinsullivan (25/2/12)

TSMill said:


> For 100% viability in the calc I need to obtain yeast 5 days into the future, which in practice I find hard to achieve.



I understand. Time travel is not one of my strong suits either. It's on my to do list, though.


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## dustinsullivan (25/2/12)

TSMill said:


> For 100% viability in the calc I need to obtain yeast 5 days into the future, which in practice I find hard to achieve.



You no longer need travel into the future, just click the checkbox, and type in your viability. 
Been meaning to do this for a long time, thanks for putting a fire under my ass.


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## ploto (28/2/12)

What would be an estimated cell count to use for the dregs in a bottle? And what sort of viability could you expect to have for something relatively fresh, such as Coopers, or for an imported bottle assumed to be in poor state?

I'm aware of the Wyeast page that MaltyHops linked to above, but I'm not quite sure how to apply it to bottle dregs.


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## [email protected] (28/2/12)

ploto said:


> What would be an estimated cell count to use for the dregs in a bottle? And what sort of viability could you expect to have for something relatively fresh, such as Coopers, or for an imported bottle assumed to be in poor state?
> 
> I'm aware of the Wyeast page that MaltyHops linked to above, but I'm not quite sure how to apply it to bottle dregs.



When i culture from a bottle its usually something like 100ml, 400ml, 800ml then into 1.5 to 2L(all just intermittent shaking), let that last step ferment out and clear at ferment temps, then wash the yeast. Using Mr malty slurry calculator get a rough idea about how many yeast cells i may have in measured sample and go from there.

I think trying to guess what live cells remain in bottle dregs would be less accurate.

How i do it is not the most accurate method, buts its repeatable and gives me some idea what im pitching.

EDIT2: I should also add i do use this calculator as well, usually when i have a more "known" sample like from a split smack pack and use the viability based on manufacture date.


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## Wolfy (28/2/12)

ploto said:


> What would be an estimated cell count to use for the dregs in a bottle? And what sort of viability could you expect to have for something relatively fresh, such as Coopers, or for an imported bottle assumed to be in poor state?
> 
> I'm aware of the Wyeast page that MaltyHops linked to above, but I'm not quite sure how to apply it to bottle dregs.


You can't apply the Wyeast info, and you can't (really) even have an estimate of the number of cells, because there are too many factors to consider that you do not know the answer to.
It's only after reviving the yeast in a starter that you'll even be sure there is _any _viable yeast.


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## ploto (28/2/12)

Thanks for clearing that up. So in other words I should just get the starter up and running first before worrying about cell counts etc.


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## Wolfy (28/2/12)

ploto said:


> Thanks for clearing that up. So in other words I should just get the starter up and running first before worrying about cell counts etc.


Yes, and even then, unless you are using microscope-techniques, any 'cell count' is simply guesswork (semi-educated estimation at best), any figures you 'calculate' will have a huge margin of error.
So, repeatable techniques, ensuring that your yeast is as healthy has possible and eliminating cross-contamination and infection are much more important considerations.

Keeping it simple; a healthy 1 to 2L yeast starter it will be more than adequate (for a standard sized batch of average gravity ale), once you have that mastered, maths and formulas may (or may not) be useful to adjust your procedures.


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## dustinsullivan (8/3/12)

Wolfy said:


> Yes, and even then, unless you are using microscope-techniques, any 'cell count' is simply guesswork (semi-educated estimation at best), any figures you 'calculate' will have a huge margin of error.
> So, repeatable techniques, ensuring that your yeast is as healthy has possible and eliminating cross-contamination and infection are much more important considerations.
> 
> Keeping it simple; a healthy 1 to 2L yeast starter it will be more than adequate (for a standard sized batch of average gravity ale), once you have that mastered, maths and formulas may (or may not) be useful to adjust your procedures.



How big a margin of error would you calculate, and what do you base this on?


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## Wolfy (8/3/12)

sulli_42 said:


> How big a margin of error would you calculate, and what do you base this on?


+/- 50% to 100%.
It's based on the assumptions required to estimate a yeast count, compared to actually counting actual yeast cells.
Then you also need to consider that when counting yeast cells the 'established' methods may not be reliable and have a large margin of error (reference 'Yeast' book and methyl-blue staining techniques).
And after that, even the published authors (compare Ray Daniels to John Palmer to Jamil Zainasheff) have vastly different suggestions on the number of cells both required and available in yeast samples - some of these are more than 10x or 100x different to each other.

Look at the MrMalty calculator as one example of the margin of error we are talking about.
For a 1.048 OG 23L brew the amount of yeast-slurry required (working on a fixed 94% viability) varies from 272ml (thin slurry, high non-yeast percentage) to 48ml (thick slurry, low non-yeast percentage) - what huge margin of error is that?
Hence, without actually counting the cells, there is no way to know - without either estimating/guessing (which is what we are talking about here) or counting actual yeast-cells - where within that range any particular yeast-sample lies.

Which is why having repeatable and regular techniques that you follow (and adjust as required) is more important than any mathematical estimate of yeast cells.


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## [email protected] (9/3/12)

Not arguing! i don't claim to have more than 1/10th of the yeast knowledge/experience as wolfy. This is just my gist on the whole yeast calc thing, there may or may not be people with similar experiences.

For me Mr Malty led me to more repeatable techniques. Sure the numbers produced are ball park at best but it gave me something to aim for and has been the single biggest noticeable improvement to my beers.

With Sulli42's calculator i thinks its a massive step in the right direction, especially if your splitting packs of yeast.
Its all very well if you brew the same batch size every time and around the same gravity to go along the lines of 1-2L starter will be sufficient, over time you can see for yourself what works and what doesn't. 

For me i brew very different types of beer one batch to the next and i would guess not nearly as frequent as a lot of people. Its usually in different volumes to account for gravity and my intended consumption of the style. So anywhere between 8 - 12L 1045 to 1075 wort. I've done three 23L batches 2 of those were for case swap.

If 6months or a year later i used the same technique that brought me decent results with my split yeast the first time when it was fresh, i can safely say that the resulting beer would not be nearly as good, as if i had of used the stepped starter calculator, especially if there is say 20 points gravity difference in the worts. It would have taken me much more trial and error over many years to work out how much yeast to pitch on different worts if these calculators were not available.

I guess my point is, just going by what has worked for me in the past blindly would produce a lesser quality beer than integrating the calculator into my regular yeast practice, in which i try to make the conditions i grow my yeast in the same every time. 

Like everything else it depends heavily on how your mind works, the calculators give me targets to aim for each step of the way, whether or not those targets are met will never be known but at least i am using the same calculations every time i grow some yeast. 

All this may sound like i take my yeast very seriously! But in reality i am fairly relaxed about the whole thing mostly because these calculators have given me consistent results i am happy with.

End morning coffee infused rant


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## dustinsullivan (9/3/12)

I agree wholeheartedly with your statement, that without actually counting individual yeast cells, there is no way to know precisely how many cells are present in a given sample. 

However, in the context of yeast propagation, most of the variables involved in cell growth are controllable; the quality of the wort, the inoculation rate of the starter, the amount oxygenation, and the temperature of the ferment, four very important factors affecting cell growth, are completely within the average home brewer’s control. 

If one maintains a constant on these four variables, and then pitches an unknown quantity of yeast into a reasonably sized starter, after the initial fermentation, there will almost always be a measurable quantity of highly viable (+98%) yeast, if this yeast is then placed in an appropriate sized graduated cylinder and chilled for about 48 hours, one should end up with a nice compact, measurable volume of yeast. According to multiple reliable sources (i.e. Fix, Zainasheff et al.), this yeast cake should contain on average; around 3 billion cells per milliliter. 

Is this method perfect? Not even close.

Is there a margin of error involved? No doubt.

But personally, I think its way less than +/- 50 to 100%, it’s probably closer to +/-25%. 

I also agree with you that having repeatable and regular techniques to follow (and adjust as required) is very important; and Beer4U’s post above is a perfect example of that.


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## Wolfy (10/3/12)

Beer4U said:


> All this may sound like i take my yeast very seriously! But in reality i am fairly relaxed about the whole thing mostly because these calculators have given me consistent results i am happy with.


That's more-or-less what I was trying to say. 
If your techniques and methods produce good beer and give repeatable results - that's the important thing - not what the exact yeast cell count is, or the margin of error.
Use a reliable and repeatable method (like this or other calculators) to give you an estimate of what is required, but then concentrate on yeast health (rather than being overly concerned about complicated mathematics and exact yeast cell counts).


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## [email protected] (10/3/12)

Wolfy said:


> That's more-or-less what I was trying to say.
> If your techniques and methods produce good beer and give repeatable results - that's the important thing - not what the exact yeast cell count is, or the margin of error.
> Use a reliable and repeatable method (like this or other calculators) to give you an estimate of what is required, but then concentrate on yeast health (rather than being overly concerned about complicated mathematics and exact yeast cell counts).



:icon_chickcheers:


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## donburke (26/3/12)

sulli_42 said:


> I agree wholeheartedly with your statement, that without actually counting individual yeast cells, there is no way to know precisely how many cells are present in a given sample.
> 
> However, in the context of yeast propagation, most of the variables involved in cell growth are controllable; the quality of the wort, the inoculation rate of the starter, the amount oxygenation, and the temperature of the ferment, four very important factors affecting cell growth, are completely within the average home brewers control.
> 
> ...



hi sulli,

have you changed your growth rate formulas on your calculator ?

i am getting what appears to be an abnormally larger number of new cells created, 

e.g. 97 billion cells into a 1.5 litre starter intermittent shaking yields a total number of 415 billion cells at the end of that step

whilst i'd love it to be that easy, i'm certain it wasnt calculating such a high growth rate previously


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## dustinsullivan (26/3/12)

donburke said:


> hi sulli,
> 
> have you changed your growth rate formulas on your calculator ?
> 
> ...



Thank you for bringing that to my attention don. I was making some modifications to the app last night, and apparently changed some parameters that should not have been changed.
I've repaired the damage, should be back to normal. Thanks again.


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## DJ_L3ThAL (18/9/13)

Fantastic thread (sorry to dig it back up!), has helped me in my understanding to create my first starter, to outline my rationale:


Used MrMalty to calculate my yeast slurry sample viability (is 10% based on being ~2 months old in fridge).
Used "rule of thumb" that there are 1.2 billion cells per mL of slurry, so at 10% viability if I used 2x 20mL slurry samples I am starting with 4.8 billion cells.
Used sulli's calculator for the beer I'm brewing and came up with 3 steps, sample into 300mL into 500mL into 800mL (so final starter volume 1.6L) will give me the required 178 billion cells to chill, decant and pitch the slurry into the fermenter once ready.
Thanks again, looking forward to tasting my 2nd All-Grain Dr.Smurto's Golden Ale using re-harvested US-05  :beer: :beer: :beer:


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## syl (18/9/13)

Just thought I'd pop in and say yeastcalc.com for stepped starters is amazing!


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