Yeast viability & stepping yeast starters

[butterman]

Hi all,

Could you please give me some insights into the following;

According to the Mr Malty calculator my Whitelabs liquid yeast has a residual viability of 27% & it recommends a starter volume of 2.08 litres.

My first question is what is the lowest yeast viability score that you think is worth bothering with for a starter?

I intend to do a stepped starter with this yeast. I understand that each step will give a diminishing return in terms of the increase of yeast numbers.

Given the above yeast viability my second question is what would you expect the maximum viability that could be achieved with it?

Thanks & Cheers
butterman

[atomicpunk]

I'm no expert but since the yeast gurus sometimes grow up from slants, I think you can step this one up to proper pitching rate. The viability is just saying you are starting with 27 billion yeast cells rather than 100 billion. I would start off with a smaller starter just to get what good yeast is left going. Maybe start off with 0.5L and step from there.

[pfooti]

Yeah, you can definitely do it. Plan on a two-step starter. You can do this with mr. malty by doing this:

1) use the given 27% viability and fiddle with the OG and volume settings until you get a suggested starter size equal to whatever your first stage starter is (500 mL maybe?). Make sure the growth-factor slider is set all the way to the right so the calc doesn't tell you to use two vials.

2) Write down the target number of yeast cells (120 billion or whatever) that the calculator gives in (1).

3) Manually set the OG, volume of the calc to the actual brew you're making.

4) Manually set the viability percentage in the calc to whatever number you wrote down in (2). So if it claims you'll have 120 billion cells after your first stage, set the viability to 120%. That's the main trick here.

5) This new volume is the size of your second step, provided you ferment the first step nearly completely, crash cool, and decant off the liquid.

I've done this a few times, mainly for my big beers that require more than 1.5L in a 1-step starter, as I only have a 2L flask. Works pretty well so far.

[jgaarder]

Yeah, you can definitely do it. Plan on a two-step starter. You can do this with mr. malty by doing this:

1) use the given 27% viability and fiddle with the OG and volume settings until you get a suggested starter size equal to whatever your first stage starter is (500 mL maybe?). Make sure the growth-factor slider is set all the way to the right so the calc doesn't tell you to use two vials.

2) Write down the target number of yeast cells (120 billion or whatever) that the calculator gives in (1).

3) Manually set the OG, volume of the calc to the actual brew you're making.

4) Manually set the viability percentage in the calc to whatever number you wrote down in (2). So if it claims you'll have 120 billion cells after your first stage, set the viability to 120%. That's the main trick here.

5) This new volume is the size of your second step, provided you ferment the first step nearly completely, crash cool, and decant off the liquid.

I've done this a few times, mainly for my big beers that require more than 1.5L in a 1-step starter, as I only have a 2L flask. Works pretty well so far.

I did that exactly just a few days ago for the first time as you've outlined. Everything went well except the second step blew out the top of my 2L flask. I was stepping up Wyeast 1007. I don't know if that would happen with any other yeast, I've read else where that 1007 really goes and it's really going in my alt right now, plenty of krausen. With fresh yeast fermentation will really take off, next time I step up a starter I think I'll use a bigger container for the second step to hopefully not lose any of that yeasty goodness.

[atomicpunk]

Foam control helps with this.

[spiderwrangler]

Agreed, foam control and loosely cover with foil.