Stepping up a starter

[JLem]

For my next brewday I wanted to make a 2-L starter...however, I only had enough DME for a 1-L starter. So, I made a 1-L starter a week ago. I went to my LHBS today and picked up more DME. So, how do I proceed from here:

1) Do I just make up another liter of starter wort and dump into my original starter? This will give me a total volume of 2-L, but adding this new liter of wort into already fermented starter will dilute the gravity of the new wort, so will yeast growth really be the same as if I had started with 2-L?

2) Do I decant the original starter and add the fresh liter of wort to the yeast slurry? This will maintain the gravity of the new wort, but my ending starter volume will obviously be less than the 2-L I was looking to make. Will the resulting yeast growth be enough?

3) Do I try something else?

 

[Larso]

For my next brewday I wanted to make a 2-L starter...however, I only had enough DME for a 1-L starter. So, I made a 1-L starter a week ago. I went to my LHBS today and picked up more DME. So, how do I proceed from here:

1) Do I just make up another liter of starter wort and dump into my original starter? This will give me a total volume of 2-L, but adding this new liter of wort into already fermented starter will dilute the gravity of the new wort, so will yeast growth really be the same as if I had started with 2-L?

2) Do I decant the original starter and add the fresh liter of wort to the yeast slurry? This will maintain the gravity of the new wort, but my ending starter volume will obviously be less than the 2-L I was looking to make. Will the resulting yeast growth be enough?

3) Do I try something else?

You could decant most of original chilled starter, then pitch 1/2 or slightly less of it into new starter. This will give you a better cell count
1 is the worst option as the alcohol in starter no1 will inhibit yeast growth

 

[ianw58]

I'm curious. Why not pitch all of th first step into the second step?

 

[Larso]

I'm curious. Why not pitch all of th first step into the second step?

Answered in edit above!

 

[ianw58]

Sorry. What I meant was, after decanting, why only use half or less of the yeast skurry?

 

[CharlosCarlies]

I'm assuming you only have a 2L flask?

I'd decant and add another 2L of starter wort.

 

[Larso]

Sorry. What I meant was, after decanting, why only use half or less of the yeast skurry?

Theres a limit to how much the yeast can multiply determined by the size of the starter(among other factors). The first starter will multiply to give you as many cells as it can from a 2L starter. If you then pitch this into the second starter you'll already have a very large amount of viable yeast and there wont be as much reproduction. Pitching a portion(say 1/3) of the slurry will allow the yeast to multiply to a greater extent as the cell count wont be already maxed out for a 2L starter.
I cant remember the exact science behind this but I got it from Jamil Whites Yeast book. The multiplication factor reduces the higher the pitching rate Vs the starter size

 

[MBTB]

Larso, it sounds like splitting the slurry from the first step into 2 second steps may yield more yeast than a triple step starter. I think it's time to get another 1 gallon jug.

 

[Larso]

Larso, it sounds like splitting the slurry from the first step into 2 second steps may yield more yeast than a triple step starter. I think it's time to get another 1 gallon jug.

If by triple step you mean decanting and adding 2l fresh wort each time, then yes you'd expect more yeast from splitting

 

[Photopilot]

I have been researching this and came up with these links and tools telling me how to get the necessary yeast count from a single tube.


http://www.yeastcalc.com/

http://billybrew.com/stepping-up-a-yeast-starter

 

[JLem]

I'm assuming you only have a 2L flask?

I'd decant and add another 2L of starter wort.

Hadn't thought of this (obviously). Sounds like the right option for my situation.

I have been researching this and came up with these links and tools telling me how to get the necessary yeast count from a single tube.


http://www.yeastcalc.com/

http://billybrew.com/stepping-up-a-yeast-starter

And this confirms the above approach...thanks! Off to make 2 liters of starter wort