# Wyeast Viability



## Crusty (26/4/13)

Just after a bit of advice on some 30ml yeast splits that are approaching 12 months old & whether they are still viable.
My normal procedure is to smack a room temp Wyeast pack & let it swell for a couple of days. Pour the pack contents into 4 x 30ml vials.
I use 200gm DME to 2lt water, stir to combine & decant 600mls into a 1lt flask & leave the 1400mls in the other flask. Boil both for 15mins, let cool & pitch 1 x 30ml vial into the 600ml starter. Place on stir plate & stir for 24hrs. After 24hrs, pour the entire contents into the waiting 1400ml flask & stir on the stir plate for another 24hrs. Decant wort & pitch yeast slurry into 20lt of wort. I normally don't use yeast any later than a couple of months but have a bit of a back log with some vials approaching 12 months old.
Anyone used splits this old or just dump them & start again.


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## mckenry (26/4/13)

Crusty,
I have used 1084 Irish Ale that is nearly 2 years old. I use yeastcalc.com though for working out starter sizes. Yeastcalc tells me the viability is 1%, as thats as low as it will go. 1084 never fails me. Always comes back from the dead!
Ive recently done a 1272 that was more than 11 months old and a 3638 that was >1 year old.

Note - my method is to smack a pack and split 3 ways. I dont wait for it to swell as I'm putting two of them straight in the fridge anyway.
I then just start one up when I want to use it. Often this is as much as a year later, but they are 'new'. I cant be arsed with washing yeast. 

So when I use yeastcalc.com I plug in 33B cells as initial cell count and the date of manufacture (I label my vials) and quite often I am starting at 1% viability.
Always works, so I wouldnt be throwing them away if I was you, just maybe look at changing your step up method?


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## mikec (26/4/13)

Yeah I've done starters from a small amount of old liquid yeast.
Add an extra step to your starter, maybe 300ml, 600ml, 1400ml, or whatever combo yeastcalc gives the best results from.
As it's old yeast be conservative re the viability - as McKenry said yeastcalc doesn't go below 1% but it could well be less than 1%.


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## mikec (26/4/13)

Worst case scenario - you get nothing from the first step, you go and buy some new yeast.

Nothing to lose by giving it a go, other than 20 grams of malt.


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## Crusty (26/4/13)

Thanks heaps guys, much appreciated.
Using yeastCalc, it seems my worst dated vial is @ 1% viability so I will need to do a 3 step starter for this one.
The best result using the calc is 1 x 30ml vial ( 1% viability, 0.25 billion cells ) into 600mls, then into 1lt then into 2lt. This will give me 224 billion cells for my 1.054 Ale. ( 200 billion needed )
Using a stir plate, are we using J. Zaineshef or the other dude, Troester?
I may have been under pitching all this time if Mr Zaineshef is on the ball.

Cheers


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## mikec (26/4/13)

I use the J. Zaineshef numbers, the other dude appears to be a new addition and by way of some kind of voodoo, get's triple the results from the same starter.


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## Crusty (26/4/13)

mikec said:


> I use the J. Zaineshef numbers, the other dude appears to be a new addition and by way of some kind of voodoo, get's triple the results from the same starter.


Thanks mikec,
I'll use Mr Z.
Cheers


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## mckenry (26/4/13)

Crusty said:


> Thanks mikec,
> I'll use Mr Z.
> Cheers


I read all the guff about the new method of calculation and I am using Troester. Thats the right one to use if you are continually stirring.


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## Crusty (26/4/13)

mckenry said:


> I read all the guff about the new method of calculation and I am using Troester. Thats the right one to use if you are continually stirring.


Really?
Who told you that?
Now I'm really confused.
According to Troester, I would only need 2 steps, 400ml to 1200ml for 225 billion cells even @ 1% viability.
I think the Zaineshef would be more true to that viability & needing a 3 step starter to get me there.
Happy to be corrected though.


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## Crusty (26/4/13)

Anyone else using YeastCalc & a stir plate wish to weigh in.


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## seamad (26/4/13)

I've raised a few from the dead recently, up to 2 years old, originally split into 1/4. Anything @ 1 year I do little steps, 50ml, 200ml, 800ml, decant and then do a 1.2 or therabouts using yeastcalc. Smaller steps I believe will result in healthier yeast. Noticed the new window on yeastcalc but just used the Z option, interested on the basis for the new one.


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## mckenry (27/4/13)

Crusty said:


> Really?
> Who told you that?
> Now I'm really confused.
> According to Troester, I would only need 2 steps, 400ml to 1200ml for 225 billion cells even @ 1% viability.
> ...


Heres a copy/paste of the guff I was talking about
But most of the various calculators out there base their data on work published in Chris White and Jamil’s yeast book. Unfortunately the yeast growth example given in that book was only for a non agitated starter. When a starter is constantly stirred all the yeast is kept in suspension in a homogeneous nutrient environment. That is not true for non agitated starters where yeast will sediment and only evolution of CO2 will cause agitation. As a result stirred and still starters are expected to show different growth behavior that cannot be simply approximated by adding a constant scaling factor to yeast growth.

The full article is here
http://braukaiser.com/blog/blog/2012/11/03/estimating-yeast-growth/


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## mikec (27/4/13)

Yeah but hold on, being on a stir plate means it is agitated, yes?
We are talking about Yeastcalc's two options for stir plates, not comparing a stir plate starter with a still starter.
Yeastcalc now has two options for Stir plate starters, with wildly different results.


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## bum (27/4/13)

Kai is a member here now, right? Perhaps someone might wish to PM him for his input?


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## Midnight Brew (27/4/13)

I still havnt got my head around it but different methods with vastly different results.

My question, is the Troester method healthy for yeast in that growth factor?

eg. 22L of 1.050 wort needs 204 billion cells.
So a 1.5L Troester starter (stirred) with 1 billion cells added (100 billion cells with a 1% viability = 1 billion lets say) yields 212 billion cells, enough for a 22L batch of 1.050 wort. Thats a gorwth factor of 217!


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## treefiddy (27/4/13)

mikec said:


> Yeah but hold on, being on a stir plate means it is agitated, yes?
> We are talking about Yeastcalc's two options for stir plates, not comparing a stir plate starter with a still starter.
> Yeastcalc now has two options for Stir plate starters, with wildly different results.



KT created a stir plate model based on experimental results.

JZ's stir plate model is simply the non-agitated model scaled up by a factor. KT believes this is not right, because the dynamics of yeast access to nutrients and sugaz is completely different.


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## mckenry (27/4/13)

treefiddy said:


> KT created a stir plate model based on experimental results.
> 
> JZ's stir plate model is simply the non-agitated model scaled up by a factor. KT believes this is not right, because the dynamics of yeast access to nutrients and sugaz is completely different.


Well put. Nice summary. I use the KT now and had my first krausen explosion recently


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## Wolfman (28/4/13)

Doesn't it have more to do with growth rate?


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