When yeast starter doesn’t necessarily grow yeast.

[hylander0]

I want to lay out a problem we as us home brewers deal with from time to time and get some feedback. Pitch rates and proper, healthy yeast propagation.

Situation: You have your 10 Gallons of 1.058 OG beer planned out. You have one healthy vial of yeast containing approx. 90 billon cells and that is the all you can get

Problem: You need 405 Billion and you can only use your stir plate & 2L Erlenmeyer flask

Facts (see source below):
Healthy Yeast Propagation Wort should be between 1.020 SP & 1.030 SP, Limit # of steps - More stepping introduces more chances for contamination and Keep as close to 72 degrees F as possible
Source

My Solution (Calculator)

1. Start and finish 1.5 L starter @ 1.030 with 90 B cells

a. Cells propagated: 262 B​

2. Decant Starter and Remove 3/4 of the slurry in to Sanitized Jar for pitching

a. Cells in Flask: 65 B​

b. Cells in Jar: 197 B​

3. Start and finished 1.5 L @ 1.030 with 65 B cells

a. Cells propagated: 209 B​

4. Decant Starter and Remove All of the slurry in to Sanitized Jar for pitching

a. Cells in Jar: 197 B + 209 B = 406 B​

5. Done

Given the growth rate is next to nothing after 200 B in a 2L flask then I would have no choice but to do this.

I would like some feedback on this conquer and divide stepping up technique. Thoughts on this? Given my situation what have to done in the past (obviously besides using a bigger flask to step up)?

 

[billl]

You can certainly do that. Personally, I don't like wasting that much wort and would just make a 1-2 gallon batch of beer that I would actually drink and then use the cake for the larger batch.

 

[day_trippr]

[...]I would like some feedback on this conquer and divide stepping up technique. Thoughts on this? Given my situation what have to done in the past (obviously besides using a bigger flask to step up)?

You did what you had to given what you had to work with. It's proper.
In the same situation I split the yeast between a pair of 2l flasks on dual stir plates...

Cheers!

 

[IslandLizard]

Or follow this alternative method.

Yes, we love our first time posters.

 

[hylander0]

Love it. Thanks for the feedback.

Brew a one gallon batch to propagate your yeast. I like it!

I have found running through calculated scenarios that growing yeast and confining yourself to a small vessel should only be done if you don't have a choice.

In the future I will be using a bigger vessel. Since this post I have found that a 1 gallon glass fermentation jug works quite nicely on my stir plate ($5 bugs vs $50 for a 5L flask). I just need to boil the wort in another container.

I will be just using a 1.5 L start and stepping up in the 1 Gallon Jug.