Stepping up a starter ?

[Lennybuzz]

Thats what I was thinking. So that will be my plan ferment for 24. Put in fridge for 24, Decant add new wort and repeat till i get the size i need. Thanks for the input.

[JSKC]

I was just thinking about this yesterday, and came up with a question...

So, if we are doing a starter, either on or off of a stir plate, we are primarily looking for growth. Though most of the time 18-24 hours is enough time to get full growth and to have it mostly ferment out, if we crash it too soon, do we give the yeast a chance to build up their reserves before going dormant? Will they build up their reserves when exposed to the cold temperatures? In the end, if we cold crash too soon, will they be healthy and ready to multiply in the final 5-10 gallons of wort?

[11amas]

I think so...in fact, I am doing this today for the first time (starter is on its third day). I will be pitching into a carboy with about 4L of wort. I should have enough for my dort...had it been a bigger beer I would have done the crash-decant bit but it would have taken a few more days.

[wunderbier]

Hey guys, when stepping up twice, I find the Wyeast Labs pitch rate calculator to be incredibly useful. http://www.wyeastlab.com/hb_pitchrate.cfm

A couple of you mentioned needing 771 billion cells in 11 gallons of of 1.050 wort. The Wyeast calculator goes by cells/ml, so that would be 18.5 million cells per ml of wort. Assuming a limit of a 3 L starter, per the Wyeast calculator, 18.2 million cells per ml of wort (758 billion cells) can be achieved from 1 activator package with two sequential 3 L stir-plate starters (SPS).

Two packages into two consecutive (slight more than) 2 L SPSs will yield 18.5 million cells per ml.

With intermittent shaking is a bit more difficult than SP or simple starter, because the Wyeast calculator doesn't have this feature. Both calculators give very similar results for SPSs and simple starters. Doing a bit of interpolation using the "intermittent shaking" result from MrMalty.com, it would seem that such a starter requires 1.54 times the volume of a SPS. So, since in the Wyeast calculator 2 SPS of 0.55 gallons from 2 packages gives the proper result, an intermittently shaken starter should have a volume of 0.846 gal (3.2 L) at each step.

So, shortly:
-For consecutive starters, use the MrMalty calculator to determine pitch rate;
-Use the Wyeast calculator to determine starter sizes and required packages;
(-Multiply SPS volumes by 1.54 if you use intermittent shaking.)

[switters]

Does this need to be so complicated, or am I missing some subtle detail?

I remember from the shows that JZ only uses a 2L flask and a stirplate for his starters. I also remember that 2L of wort and 1 vial of yeast on a stirplate approximately doubles the cell count.

In one of the shows I believe there is some discussion about starters that are very large in proportion to the number of cells have an effect on yeast growth. I don't think it was a negative effect, but growth was not linear. This may already be incorporated into the calculator.

[JKoravos]

Does this need to be so complicated, or am I missing some subtle detail?

I remember from the shows that JZ only uses a 2L flask and a stirplate for his starters. I also remember that 2L of wort and 1 vial of yeast on a stirplate approximately doubles the cell count.

In one of the shows I believe there is some discussion about starters that are very large in proportion to the number of cells have an effect on yeast growth. I don't think it was a negative effect, but growth was not linear. This may already be incorporated into the calculator.

What are you considering complicated?

Also, it only takes 1 L on a stirplate to double the cell count of a vial.

[Cuddly_Gus]

I though I had it all straight in my head until I compared Jamil's calculator with the one on Wyeast's site... Ugh!

My example is a 1.064 Scotch Ale. Batch size is 11.2 gallons and I use a stir plate, propagating from a single vial or pack of yeast. (5000mL Erlenmeyer)

Using Jamil's calculator:
# of cells needed = 496 Billion cells
# of vials needed = 3 (for 3.8 l starter)

Step1: Grow 100B cells to 300B cells
Volume of starter = 3.8 l

Step2: Grow 300B cells to 496B cells
Volume of starter = 5.1 l

Hence this is a 2-step starter:
1) Prepare a 3.8l starter with single vial of yeast
2) Chill and decant beer off the yeast
3) Add enough new wort to make a 5.1 l starter
4) Chill and decant beer off the yeast
5) Pitch yeast to fermenter

I'm happy here. Now comes the comparison part

When I plug these 3.8 l and 5.1l steps into the Wyeast calculator, the end result is 22.29 Mcells/ml. Multiply by the batch size (converted to ml) and you get 945B cells (compared to 496B cells from Jamil's calculator).

I know there is one main fundamental difference between the 2 approaches: Jamil's model assumes a beer decant for each step, whereas Wyeast has you pitch new wort on top of beer from the previous step. But it makes no sense to me how that could DOUBLE the cell count... It's almost as if Wyeast assumes the yeast have consumed zero sugar from the initial wort....

My inclination is to trust the Wyeast numbers since it is a calculator specifically designed for stepping, whereas, we're making assumptions about Jamil's tool. But I'm also of a mind to err on the side of conservatism (i.e. Jamil) Guess I have some experimenting to do.

[JKoravos]

Unfortunately, this is all fuzzy math. I wish I understood yeast well enough to figure this all out on my own, but I don't. When I use a pitching rate calculator I realize that it's a very rough estimate. I assume there's probably something like +/-50% between what the calculator tells me and what I actually end up with.

As for who to trust. I don't know. Maybe Jamil could give us his take on how his calculator compares to WYeast's. Pope?