[roguejim]

So I got my stir plates working.  Time to use them.  My yeast, unfortunately, isn't the freshest.  The WY2206 is dated 4-24-12.  The WY2278 is dated 2-01-12.  (The yeast calculator indicates only 13% yeast cell viability in the WY2278!)  Anyway, how long will a 1.5L starter take to ferment out before I step it up?

[Poobah58]

Took me about 10 days to step up 4-yr old Farmhouse Ale yeast to 3.6L. Yours should be a piece of cake!

[Pinski]

Check out the yeastcalc.com calculator. It will help you figure out the steps you need. I would say about 32-36 per step

[bluesman]

If your fermenting at room temp (72F), it should only take about 2-4 days to completely ferment the initial starter.

[a10t2]

Just double-checking the math... the rule of thumb is 25% viability loss per month (refrigerated), so the 2206 would be about 70%, and the 2278 about 35%. Not that it will make a huge difference in the sizes of the starters.

[kylekohlmorgen]

Can you just base it on time? Wouldn't temperature also be a factor?

[roguejim]

Just double-checking the math... the rule of thumb is 25% viability loss per month (refrigerated), so the 2206 would be about 70%, and the 2278 about 35%. Not that it will make a huge difference in the sizes of the starters.

I guess it depends on whose calculator one uses?  This one ( http://www.yeastcalc.com/index.html ) indicates only 13% viability for the 2278.  I've emailed Wyeast to see if this would be an accurate number, assuming the yeast has been properly stored by the LHBS.  I pitched the 2278 into a 1.5L starter.  Would one more step be adequate?  How large would you make the next step?

[roguejim]

Just double-checking the math... the rule of thumb is 25% viability loss per month (refrigerated), so the 2206 would be about 70%, and the 2278 about 35%. Not that it will make a huge difference in the sizes of the starters.

I guess it depends on whose calculator one uses?  This one ( http://www.yeastcalc.com/index.html ) indicates only 13% viability for the 2278.  I've emailed Wyeast to see if this would be an accurate number, assuming the yeast has been properly stored by the LHBS.  I pitched the 2278 into a 1.5L starter.  Would one more step be adequate?  How large would you make the next step?

I received a quick email from Jess at Wyeast.   He states, "Jim,
 
It is really hard to estimate this number.  I do not agree with the calculator's percentage numbers you are using (likely the Mr. Malty calculator).  I don’t like to give estimations because it is so variable and the only way to know this number is to actually analyze it.  If you must plug in a number, I would use 75%, though I will not guarantee this is the actual viability.
 
Does that make sense?
 
Please let me know if you have questions."
 
 
Jess Caudill
Brewer/Microbiologist
Wyeast Laboratories, Inc.
P.O. Box 146
Odell, OR  97044  USA
Phone:  541-354-1335   Fax:  541-354-3449
jess@wyeastlab.com
www.wyeastlab.com

[roguejim]

So, now I'm wondering what value an online yeast calculator has when it can estimate a yeasts viability at 13%, and the yeast lab guesstimates the viability closer to 75%.  Talk about a disparity in numbers.  So, who do you trust? 

[Poobah58]

I'm confused why you need to know? Start it a few days in advance and let it ride. If it's done early put it in the fridge. Decant the morning of the brew and add a little more starter to give it a head start...

[morticaixavier]

I'm confused why you need to know? Start it a few days in advance and let it ride. If it's done early put it in the fridge. Decant the morning of the brew and add a little more starter to give it a head start...

because when he pitches the yeast into 1.5 liters of starter wort he will end up with about twice the amount of viable yeast as he started with. so if he's only got a few billion cells and he needs 200 billion 1.5 liter single step isn't going to cut it, he will need at least a second step fermented out more or less completely to hit the population he wants. but if he's got 100 billion viable cells into 1.5 liters it will probably be sufficient to get his target population.

[a10t2]

because when he pitches the yeast into 1.5 liters of starter wort he will end up with about twice the amount of viable yeast as he started with.

Probably not. If you start with 100B and end up with 200B, then starting with, say, 30B would probably result in more like 130B. Give or take some pretty enormous tolerances.

[roguejim]

For me, the point now is how to determine the starting yeast cell count when the "experts" are so far apart in their numbers.  If you don't know your starting point, the rest is somewhat of a crapshoot.  I emailed Jamil about Jess's numbers.  He responded that Jess is assuming perfect storage/handling when the yeast leave the lab, and is not considering the nutritional deficiency of the "smack pack" medium over several months.  Jamil's numbers are based on empirical evidence from numerous smack pack/vials that he analyzed.

[tygo]

Unless you have the ability to count cells it's a very broad estimate anyway.  I use the Mr. Malty/Yeast Calc viability estimate and build my starters off of that.  My yeast storage conditions are generally consistent. If I don't like something about the fermentation profile of the beer I made using that size starter, the next time I make it I'll make it smaller or larger.

[Poobah58]

I think people get too caught up in yeast cell count. To me, if you have a 2L starter it does not matter how many cells you started off with you still have a 2L starter (as long as the yeast has finished). My guess is if you had a flask with a pack that was 75% viable and another flask with a pack that was 25% viable they will end up with approximately the same cell count. The 25% viable pack will just take a little longer. So why bother trying to figure out how many cells you have. Just figure out how many mL of starter you need for a given brew...