Yeast starter puzzle...

[Cellarbrau]

-You have a 5 month old smack pack of Wy2487 Hella Bock.
-It showed swelling 8 hours after activation.
-You need to pitch a 1.054 lager in 36 hours.
-You have a stirplate, wort, nutrients and various sized flasks to work with.

How do you propagate the yeast for the best possible pitch?

 

[phoenixs4r]

That's a lager yeast eh? Run a calculator and see how big of a starter you would need. I'd say for 36 hours your best bet is to pitch at high Krause but considering its age and the amount of starter wort needed to do a lager I would probably just push back the brew day.

 

[Cellarbrau]

It is a lager yeast strain and using a calculator is sound advice. You had a C+ but pushing back the brew day is an automatic fail. Good try though.

 

[Cromwell]

I'd step it. Make a 1L starter now, give it 19 hours, pitch that in 2L then in 36 hours pitch the whole starter. Probably only a B- answer, but my understanding is yeast replicate in about 24 hours, so I'm guessing you can nearly double your yeast count twice in the time you have.

 

[phoenixs4r]

Good luck, and an F for your planning capabilities.

 

[OldWorld]

Brew a low gravity beer and appreciate it in this hot weather we are having in the USA...That's what ya do

 

[Cellarbrau]

I'd step it. Make a 1L starter now, give it 19 hours, pitch that in 2L then in 36 hours pitch the whole starter. Probably only a B- answer, but my understanding is yeast replicate in about 24 hours, so I'm guessing you can nearly double your yeast count twice in the time you have.

That is a pretty good answer. S. cerevisiae doubling time is actually much less than that, under 2 hours under the right conditions.

Brew a low gravity beer and appreciate it in this hot weather we are having in the USA...That's what ya do

That may be really good advice however it doesn't answer the question

This isn't a "save my brewday" thread. It's just a puzzle for ya'll to work on.

 

[Sulli]

Make a 2 liter starter, spin for 10 hrs @ 90 degrees;
step up to 4 liters, spin for 10 hrs @ 90 degrees;
Chill for 16 hours, decant and pitch.

 

[ResumeMan]

Any number of ways to solve this puzzle, really. The main problem is the shortage of time. Let's assume that Yeastcalc.com has the right calculations. We'll choose some numbers that will provide a bit of a buffer in the total number of cells, in case our compressed schedule doesn't allow quite as much growth as the calculator says. Also assume that "various size" flasks goes up to at least 4 l

So:
Lager yeast, 1.054 gravity you need 397 billion.
5-month old pack of 100-billion cells is 10% viability, so 10 billion to start with.

If you do a 2-liter starter and step it up to a 4-liter starter, you end up with 409 billion (amazing, huh?)

So: Make a 2-liter starter at around 1.040 right in the 4-l flask, and let it do its thing for about, oh, 14 hrs. Hopefully that'll let most of the potential growth happen, and keeps us on schedule.

Make up 2 more liters at a gravity of about 1.070 and just dump it in on top of your other starter. Assume that the original starter went from 1.040 > 1.010 or thereabouts, so if you double the volume with almost twice the sugar, you have a new, larger starter at 1.040 or so. You'll be in the ballpark anyway.

Let that run for 14 hrs. Toss it in the fridge for 6 hrs to crash, take it out 2 hrs before pitching time to warm up to the right temp. 14+14+6+2 = 36

What's my grade?

p.s. I'd just go buy more yeast or push back brewday, or plan ahead better, but that's me...

 

[Cellarbrau]

Resumeman gets....

nestar:

A gold star!

For the best answer so far.

 

[wegz15]

Me personally....make a starter and count yeast/check viability. Delay brew fast if I had to,but I have equipment to do that.