Starter Step up discussion

[arringtonbp]

What is the advantage/purpose behind stepping up to a certain sized starter rather than just pitching the small amount of yeast into a large starter?

Is it simply to save money?

 

[periwinkle1239]

Yeast growth is exponential. So by making a 1 L starter and then stepping it up with another 1 L addition will give you more cells then only doing a 2 L starter. It's not just a 'doubling' affect when you step. Stepping up may be desirable for big beers, whereas a 2 L without stepping might be just fine.

 

[arringtonbp]

That's interesting. So if I step up the dregs from a bottle from a very small volume, theoretically I'll have a larger amount of yeast than if I just dump the dregs into a huge wort starter?

 

[helibrewer]

When you do stepup's you must dilute the cell count to about 50 million cells per ml or you just won't get much growth.

1 smakpack in 2L yields considerably more yeast than 1 smackpack in a 1L starter. Cell density (cells per ml) is critical to starter growth. A 1L starter stepped up to another 1L will not yield as much as a single 2L starter.

To properly stepup a 1L starter you would need to go from 1L to 2L. A 2L step-up should be to 4L. Each step-up should redilute the count to about 50 million/ml or you just won't get much growth.

 

[elpenoso]

Check out his calculator it might clear some things up http://www.yeastcalc.com/

 

[jtejedor]

I think most do it because of lack of space. If you have the space I say do the 1 large starter instead of stepping up.

 

[Dhruv6911]

Yeast growth is exponential. So by making a 1 L starter and then stepping it up with another 1 L addition will give you more cells then only doing a 2 L starter. It's not just a 'doubling' affect when you step. Stepping up may be desirable for big beers, whereas a 2 L without stepping might be just fine.

Are you sure about this? Yes yeast and all other cells grow exponentially because they double. We must remember that the alcohol they put out is toxic to them in high doses. So if you start out with 1L starter instead of two, the yeast are going to be at a higher density and therefore make a harsher environment for them very fast causing them to become inactive/die. The second step will reactivate them, but i suspect there to be a plateu during the transition. Whereas a 2L starter allows the cells to grow for an extended period (More cell growth) before hitting that alcohol/harsh environment limit. Therefore i would assume a 2L initial starter is better then doing a 1L step up from a 1L starter. Now i know there are factors that i am leaving out, such as oxygen which is a good reason to do the steps, but i was assuming that a stir plate is being utilized.

 

[periwinkle1239]

Are you sure about this? Yes yeast and all other cells grow exponentially because they double. We must remember that the alcohol they put out is toxic to them in high doses. So if you start out with 1L starter instead of two, the yeast are going to be at a higher density and therefore make a harsher environment for them very fast causing them to become inactive/die. The second step will reactivate them, but i suspect there to be a plateu during the transition. Whereas a 2L starter allows the cells to grow for an extended period (More cell growth) before hitting that alcohol/harsh environment limit. Therefore i would assume a 2L initial starter is better then doing a 1L step up from a 1L starter. Now i know there are factors that i am leaving out, such as oxygen which is a good reason to do the steps, but i was assuming that a stir plate is being utilized.

Yes, however there was one thing I failed to mention in my first post. I agree with you about the harsher environment. But when I step up, I always decant off the first 1 L liquid before adding the second 1 L, therefore reducing the 'harsh' environment.

Also, exponential does not mean doubling. Doubling is 2x, exponential functions are e to the x power.

Last, not that you should rely solely on a home brew supplier says, but check out what Northern Brewer has to say about yeast starters: http://www.northernbrewer.com/documentation/YeastStarter.pdf

"To increase pitching rates even more for very strong beers or larger batches,
allow the starter to ferment completely. Chill the flask to cause the yeast
to settle, then decant the spent wort and add more boiled and cooled wort.
Remember to follow strict sanitation procedures! Stepping up a 1000ml
starter with an equal amount of wort will produce an even higher cell count
than a plain 2000ml starter."

Respectfully.

 

[periwinkle1239]

A 1L starter stepped up to another 1L will not yield as much as a single 2L starter.

I respectfully disagree assuming you decant off the spent wort.

 

[helibrewer]

I respectfully disagree assuming you decant off the spent wort.

It's explained pretty well in Yeast by White and Zainasheff.

Basically your first 1L starter (with a starting density of 100 million per ml) has about 155 billion cells now (.5 doubling factor). When you decant and put this in another 1L starter your popluation concentration is about 155 million cells per ml which is 3X the desired concentration...there will be very little growth at that cell density.

A 2L starter has a cell density of 50 million per ml with a 1.1 doubling factor...that yields about 220 billion cells....you will be lucky if your (2) 1L starter step yields 200 billion.

You would be far better off decanting the 1L into a 2L, at least in that case you get the density down to about 75 million per ml.

 

[periwinkle1239]

It's explained pretty well in Yeast by White and Zainasheff.

Basically your first 1L starter (with a starting density of 100 million per ml) has about 155 billion cells now (.5 doubling factor). When you decant and put this in another 1L starter your popluation concentration is about 155 million cells per ml which is 3X the desired concentration...there will be very little growth at that cell density.

A 2L starter has a cell density of 50 million per ml with a 1.1 doubling factor...that yields about 220 billion cells....you will be lucky if your (2) 1L starter step yields 200 billion.

You would be far better off decanting the 1L into a 2L, at least in that case you get the density down to about 75 million per ml.

Very interesting thanks for the input. Should someone send NB a message that they should revise their instruction sheet?

 

[jww9618]

It's explained pretty well in Yeast by White and Zainasheff.

Basically your first 1L starter (with a starting density of 100 million per ml) has about 155 billion cells now (.5 doubling factor). When you decant and put this in another 1L starter your popluation concentration is about 155 million cells per ml which is 3X the desired concentration...there will be very little growth at that cell density.

A 2L starter has a cell density of 50 million per ml with a 1.1 doubling factor...that yields about 220 billion cells....you will be lucky if your (2) 1L starter step yields 200 billion.

You would be far better off decanting the 1L into a 2L, at least in that case you get the density down to about 75 million per ml.

According to yeastcalc.com. Say you start with 1 vial of yeast (100 billion cells) and your yeast is 1 month old (75% viability) and assuming you're using a stir plate for all starters here are the numbers.

1L starter stepped to another 1L starter:
Starting cells: 75 billion
1st step: 196 billion
2nd step: 330 billion
Ending cell count: 330 billion

2L starter:
Starting cells: 75 billion
Ending cells: 269 billion

In summary, doing a 1L starter stepped into another 1L starter will create 61 billion MORE cells than just making a 2L starter.

 

[helibrewer]

According to yeastcalc.com. Say you start with 1 vial of yeast (100 billion cells) and your yeast is 1 month old (75% viability) and assuming you're using a stir plate for all starters here are the numbers.

1L starter stepped to another 1L starter:
Starting cells: 75 billion
1st step: 196 billion
2nd step: 330 billion
Ending cell count: 330 billion

2L starter:
Starting cells: 75 billion
Ending cells: 269 billion

In summary, doing a 1L starter stepped into another 1L starter will create 61 billion MORE cells than just making a 2L starter.

I'm just repeating what Chris White and Jamil found through research. According to these charts on the yeastcalc site: http://www.yeastcalc.com/growthcharts.html
you can see that lower initial cell densities give you exponentially higher growth rates. The lower the innoculation rate, the better the growth which is really the point I'm trying to make...putting more an more yeast into the same volume has diminishing returns.

 

[Dhruv6911]

Yes, however there was one thing I failed to mention in my first post. I agree with you about the harsher environment. But when I step up, I always decant off the first 1 L liquid before adding the second 1 L, therefore reducing the 'harsh' environment.

Also, exponential does not mean doubling. Doubling is 2x, exponential functions are e to the x power.

Last, not that you should rely solely on a home brew supplier says, but check out what Northern Brewer has to say about yeast starters: http://www.northernbrewer.com/documentation/YeastStarter.pdf

"To increase pitching rates even more for very strong beers or larger batches,
allow the starter to ferment completely. Chill the flask to cause the yeast
to settle, then decant the spent wort and add more boiled and cooled wort.
Remember to follow strict sanitation procedures! Stepping up a 1000ml
starter with an equal amount of wort will produce an even higher cell count
than a plain 2000ml starter."

Respectfully.

Yes, but those generalized statements do not take into consideration equipment being used, such as a vortex to introduce oxygen. And you might want to brush up on your math before lecturing me on what the difference between doubling and exponential growth is.

Just because something is doubling does not mean it is not exponentially growing.
Generation(G) Cell Population (N)
N 1->2->4->8->16
G 1->2->3->4->5

Formula for "Doubling" is Nf=No*2(t/d) <- There's your exponential formula for "Doubling," not 2x now is it?
Ex. With a current population of 2 cells (No) we want to see how many cells there will be in 3 days (T=3) for yeast cells with assumed doubling rate of 24 hours (1)

Nf=2*(2^(3/1))
Nf = 16

What do you know, matches the "doubling" above at generation 5.

t = 24 hour unit days
d = doubling rate
No = initial population
Nf = final/calculated population.

As a scientist i do this for a living...

 

[Buna_Bere]

this chart I found online might help

 

[periwinkle1239]

Yes, but those generalized statements do not take into consideration equipment being used, such as a vortex to introduce oxygen. And you might want to brush up on your math before lecturing me on what the difference between doubling and exponential growth is.

Just because something is doubling does not mean it is not exponentially growing.
Generation(G) Cell Population (N)
N 1->2->4->8->16
G 1->2->3->4->5

Formula for "Doubling" is Nf=No*2(t/d) <- There's your exponential formula for "Doubling," not 2x now is it?
Ex. With a current population of 2 cells (No) we want to see how many cells there will be in 3 days (T=3) for yeast cells with assumed doubling rate of 24 hours (1)

Nf=2*(2^(3/1))
Nf = 16

What do you know, matches the "doubling" above at generation 5.

t = 24 hour unit days
d = doubling rate
No = initial population
Nf = final/calculated population.

As a scientist i do this for a living...

Ha you're right!