One Gallon Starter?

[WillieBananas]

I'm a little short on time for my planned brew day this Sunday. I'm planning on making a Bo Pils. I need to make a 4L stater. Using WLP802. I have a stir plate and a gallon carboy with a flat bottom. My question.. Instead of stepping up the starter over the next couple of days (running out of time). Should I just had two packs of yeast to my gallon starter?

 

[FunkedOut]

That'd be more than good.
If the yeast pack is fresh (has 100 billion cells), a single pack in 4L would suffice.
That's a 25 million per mL inoculation rate.

 

[Nagorg]

Batch size? Estimated OG???

 

[WillieBananas]

6.5g 1.050ish

 

[LarMoeCur]

A month old lager yeast pack will only be about 70-80% viable. So, if your yeast is 2 months old it’s about 57% viable. Starting with 57- 75 billion cells in one 4l starter will not be enough. If you are targeting 1.5 million cells per degree plato (457 billion cells). One 4l starter will yield around 328 billon cells at 78% viability. You will be 1.29 billion cells short of your goal.

You can do a couple of work arounds.

One, pitch 2 packets of yeast in a 4l starter (140 billion cells) will get 483 billion. You need to start with minimum of 130 billion viable cells to get to the 457 billion mark in one starter.

Two, if you are starting with 60% yeast packet (60 billion viable cells) do a 1l starter today and step up to a 2l starter tomorrow. You will get 456 billion cells just 1 billion below ideal. A one liter start will finish and clear in just about 20 hours. By the time you are done brewing on Sunday your 2l step up will be completed. These are all stir plate numbers so, if you are doing starters differently these numbers drop dramatically.

Easiest way is to hit up the homebrew shop for a second pack of yeast.

 

[bleme]

Two, if you are starting with 60% yeast packet (60 billion viable cells) do a 1l starter today and step up to a 2l starter tomorrow. You will get 456 billion cells just 1 billion below ideal. A one liter start will finish and clear in just about 20 hours. By the time you are done brewing on Sunday your 2l step up will be completed.

I'm sure you are right, but my brain is having a hard time wrapping around the idea that yeast given a total of 3 liters of building materials will out perform the same yeast given a total of 4 liters of building materials.

 

[LarMoeCur]

Yeah, it's one of those weird ones. I’m mostly going by what my yeast calculator spits out. But from what little I know about yeast, in a nutshell, it's about the starting number of viable yeast cells at the beginning of the growth phase (log phase). Store bought yeast is not always in the best of heath. Viability can be very low depending on the age of the yeast and how it was treated. If you only have 30% healthy yeast then it doesn’t matter how much wort you throw them in. They can only replicate a certain number of times before the growth phase ends or the cell wall becomes too scared or the envorinement becomes to toxic. Daughter cells may or may not replicate to full capacity. Glycogen reserves may get used up to rapidly with suspect yeast, the membranes may not be permeable enough. There are just too many variables to account for. I just know you get more yeast with two growth phases than one.

 

[Nagorg]

The OP didnt tell us the production date of the yeast so viability can only be a SWAG. There are also different results depending on the calculator you use.

I used to use Mr. Malty exclusively but I personally believe it's a bit too conservative and tends to over calculate what you need. I've been using the calculator on BrewUnited lately and its given me good results.

http://www.brewunited.com/yeast_calculator.php

According to this calculator, assuming ~62% viability (mfg date of 04/15/2018) and a 5L flask (assumed this because the OP is thinking of a 4L starter) and a stir-plate, you only need a 2.5L starter if you have 2 packs of yeast. (No step-up required!)

By comparison, Mr. Malty says you would need a 4.3L starter with those same two packs of yeast. (Again, no step-up required.)

If you wanted to split the difference you could do a 3.4L starter with that same yeast and no step-up. If you do have a 5L flask, I'd do that!

EDIT: I just read the OP and see that you have a 1G carboy for your starter. In that case, make the 2.5L starter and brew on!

 

[WillieBananas]

Thanks for all the input everyone! I went with a 3.75 stater and two packs of yeast. FYI the yeast harvest date was 1\23.

 

[Nagorg]

Thanks for all the input everyone! I went with a 3.75 stater and two packs of yeast. FYI the yeast harvest date was 1\23.

Good luck with that starter size in your 1G (3.79L) carboy! With that yeast age, a stepped up starter would have been better but I get the time crunch!

Happy brewing and let us know how the start time is...

 

[LarMoeCur]

The OP didnt tell us the production date of the yeast so viability can only be a SWAG. There are also different results depending on the calculator you use.

I used to use Mr. Malty exclusively but I personally believe it's a bit too conservative and tends to over calculate what you need. I've been using the calculator on BrewUnited lately and its given me good results.

I bounce around between Mr. Malty and Brewer's Friend calculators. MM doesn't show you step up numbers, which I like to see because I can never get fresh yeast. I've never had a fermentation issue using the MM yeast count numbers. It's hard to argue with the guy that wrote a yeast book, won more competitions then anyone else, and now has a pretty successful commercial brewery. It might be worth an email to ask him if he inflated the numbers to account for the homebrew factor.