Cell Creation for Older Yeast

[WBB]

So I bought WLP066 London Fog a while back and forgot about it. It got pushed to the back of the fridge. Anyways, I was gonna spin up a 1L starter and use it for a Northeast IPA. The born on date was April 24 2019 and best by Oct 21. When I put it in the yeast calculator it said viability was 0%. Crap.

I said what the hell and still spun up a 1L starter, shaken not stirred. It’s been about 28 hours and it certainly has life.

Question, if the yeast calculator initially said 0%, how do I know how many cells are viable now? Should I crash, decant and spin up another 1L starter and call it good for a 5 gallon batch with an estimated OG of 1.072?

 

[BeerFst]

I overbuild my starters, keeping 50-100B cells and often have these sitting in my fridge for 6+ months. Just did a stout last week with a sample from January this year, and like yours it’s clearly fermenting. I’ve arbitrarily been using 3b for my starting count. And it’s seemed to always work from there. No under pitch issues, fermentation well under way by the next morning.

My normal process for these older ones is to start with 500ml or less and typically drop my starters sg down to 1.03 to reduce stress on the yeast. I’ll give that a day, sometimes observing very little co2 creation (I’m on a stir plate) and the following day add 1-1.5l of slightly stronger sg, 1.040-1.050. My thought process being the existing 500 will dilute the addition to normal 1.036-1.040.

There are other calculators that can help estimate cell count using volume of yeast and an estimated density but I’ve never used them

 

[RM-MN]

Assumptions are made when the yeast calculator was written and the yeast don't always follow these assumptions. There is conflicting information on yeast viability. Yours didn't read the part about all dying in 6 months.

 

[cactusgarrett]

I experienced the same with a pack of Omega Bayern. It had a date of February, but spun it in a starter, stepped up two levels, and it just fermented a festbier perfectly fine.

For counts and starter gravity, I assumed the worst case scenario considering it DID have life, so plugged 1% viability into the calculators.

 

[kh54s10]

I would need to research some but I read some good reasons that a step starter with the same volume as the first doesn't really help much. The second step needs to be larger than the first.

 

[cactusgarrett]

I'd like to see the reference for that, as i can't wrap my head around that. Seems like going from, say, 1M cells to a 10B in a 1L starter, decanting, then putting that 10B cells into another 1L starter should definitely work to increase count.

Also, stepping up gravity seems to help, too. At least per the calculators (i'm not performing actual counts).

 

[kh54s10]

I'd like to see the reference for that, as i can't wrap my head around that. Seems like going from, say, 1M cells to a 10B in a 1L starter, decanting, then putting that 10B cells into another 1L starter should definitely work to increase count.

Also, stepping up gravity seems to help, too. At least per the calculators (i'm not performing actual counts).

I don't remember where I saw that. It was on HBT forums.
When I do stepped starters I am usually starting from just 5 ml of yeast from my frozen yeast bank. The first is smaller and lower in gravity than the second and third. Sometimes when making just a 2 step the gravities will be the same but the second step is always larger.

 

[hottpeper13]

Put different size steps in a calculator and look at the growth factor. It's really low when you do it the way Cactus says. Yes you are getting more yeast but not like when you do the x 10 rule.....15 ml into 150 ml into 1500 ml all with growth factors of +5.

 

[kh54s10]

It may just be growth factor. I use this calculator: http://www.yeastcalculator.com/

I just input some numbers and made the step sizes the same. One liter for each = Growth factor of the first step is 2.69. The second step is .54
.5 liter for the first step gives a growth factor of 1.34. Then a 1.5 liter second step gives a growth factor of 1.72

If nothing else this appears to me that the second version would be healthier. I could be wrong or it could make no difference. I guess the main thing is pitching a proper amount of healthy cells to match the gravity of the wort.

 

[WBB]

It definitely went through the growth phase. After about 36 hours, it was mainly flocking out, so I put it in the fridge. Since it was an initial 1L starter, I’m going to do another starter at 1.5L and send it up to the main stage.

 

[BeerFst]

I don't remember where I saw that. It was on HBT forums.
When I do stepped starters I am usually starting from just 5 ml of yeast from my frozen yeast bank. The first is smaller and lower in gravity than the second and third. Sometimes when making just a 2 step the gravities will be the same but the second step is always larger.

I think I recall the same thing. IIRC the general idea was that yeast can’t continue to grow to infinity in a given Volume/sugar concentration. Eventually the population will stabilize to have just enough cells to consume the available sugar and won’t keep multiplying or at least won’t do it in a healthy way. Basically yeast doesn’t suffer from the tragedy of the commons