Yeast starter

Time wise, depends on your brew day..

And yeah, a 6 month old pack of yeast, will be that low probably. It should only need around a day or so on the plate. Chill it, decant the wort, and step it up to a bigger starter. Rinse and repeat...

 

The yeast calculator on the Mr. Malty website assumes a yeast cell viability loss of 21% per month. This is a grossly conservative estimate. Your Wyeast package of May 2013 will have a lower yeast cell count but it will not be 10%.

Doing a step starter is a conservative thing to do.

Your choice.

Cheers!

 

I have found yeastcalc.com to have a more user friendly calculator for making step starters. You should get the same result as mrmalty but the steps are a little easier to compute. Of interest, yeastcalc shows your viability at 24% instead of mrmalty's 10%.

In theory, you can grow yeast to any size (of course there are some practical limits). It's too late now, but you will reach your goal quicker if you start with something larger than 1L. And remember, yeast growth is non-linear. Your second starter will have different innoculation/growth rates than your first starter, so don't expect your second step to be double your first. Fortunately the calculator can handle this with a minimum of math frustration. Yeastcalc will even take the results from first step and plug them into the second starter. It will also compute how much DME is required at each step.

Regarding yeast health, you will know fairly quickly from your starter if the yeast can be re-activated (my guess is it will take off). My experience with a stir plate is the growth seems to finish up in less than 24 hours. But taking such a small amount to ~300 billion will take a lot of steps and a lot of DME. Even a new packet of yeast would require at least a 2L starter so you are pretty much locked into making starters.

EDIT: Just played with mrmalty some more and discovered that it defaults to 10% viability for anything over 4 months (all yeast from 4-12 months shows 10%), then after 1 year of age it defaults to 1%.

 

This is just my suggestion...but save yourself some trouble and buy a fresher yeast packet.

 

Since you already have the yeast, make your starter as planned ...and then pitch it into a ~1.040 session beer first (similar color) and a week from now just pour the new (1.077 wort) on top of the whole cake in the old bucket...and make sure you use a blowoff tube...you'll need it. Did this with a Barleywine a couple years ago that turned out excellent.

 

You have said this more than once. Where did you get the idea that this is a grossly conservative estimate? White Labs (who you seem to trust about almost everything) says otherwise...

"What is the shelf life of White Labs Yeast?"
"After 30 days in the vial, the viability of our yeast is 75-85%, which is very high for liquid yeast."
http://www.whitelabs.com/faq/beer-amateur

Mr. Malty's estimate at 30 days is 76% viability, which is within White Labs' own stated range.

 

I posted the below in a previous thread:

“Peter, the Mr. Malty calculator has an assumption that 21% of the yeast cells die per month. I had a conversation with Dr. Chris White on this topic at the recent NHC in Philly. He informed me that this value of 21% is very conservative. There is no easy answer to what rate yeast cells die over time since it is yeast strain dependent.

Dr. Chris White also informed me that after a 4 month timeframe there are still plenty of yeast cells alive in their vials (but needless to say it will be less than a fresh vial).”

Cheers!

 

If this is so, perhaps he should update* his own web site FAQ so that it doesn't directly conflict with what he apparently told you. Although the FAQ numbers seems to be data based, as opposed to off the cuff remarks.

*in fact the FAQ was recently updated. But somehow this information survived.

 

Wow, I wonder if in addition to age, if the myriad of yeast handling practices, and delivery schedules in the real world were taken into account for any algorithm involving yeast survivability...much ado about nothing...these are really only rough guesstimates unless you are willing to break out a microscope... YMMV

 

Well, that's kind of the point. Since there's no practical way to know exactly how much viable yeast you have, the next best thing is an estimate, which is better than not estimating.

 

An estimate that is based upon non-conservative assumptions is best.

Cheers!

 

An estimate that is based on data would be best. I'm assuming that's what White Labs' published range is, since they actually quoted numbers.

 

my voodoo is better than your voodoo : )

 

"What is the shelf life of White Labs Yeast?"
"After 30 days in the vial, the viability of our yeast is 75-85%, which is very high for liquid yeast."

A fairly broad range of values in the above. A value of 85% means that there was a viability loss of 15%. The value of 75% means that there was a viability loss of 25%. I am assuming the range is dependent on yeast strain per my discussion with Dr. Chris White. The ‘problem’ with using a conservative estimate of 21% is that is cumulative.

Let’s consider the various assumptions in the Mr. Malty yeast calculator using a Wyeast smack-pack. Firstly, the Mr. Malty yeast calculator assumes that a brand new Smack Packs has 98.33 billion yeast cells. This starting value is grossly conservative. A brand new smack pack will have something like 120-130 billion yeast cells.

An article in BYO states: “Wyeast’s 125 mL Activator packs are advertised to contain 100 billion cells, but actually average around 120–130 billion cells, according to Les Perkins, microbiologist and quality control manager for Wyeast.”

So, for the sake of discussion let’s first consider a one month old Wyeast Smack Pack. Since the Mr. Malty yeast calculator assumes a 21% loss the number of yeast cells is considered to be 76.96 billion yeast cells. Let’s consider a more realistic starting value of 125 billion yeast cells (the mid-point of 120-130 billion) and a viability loss of 15%. The number of yeast cells in that smack pack would be 106.25 billion yeast cells. The percentage difference between 106.25 billion yeast cells and 76.96 billion yeast cells is 38%. A difference of 38% is significant.

Now, let’s discuss the case of a two month old Wyeast Smack Pack. The Mr. Malty calculator provides a value of 55.31 billion yeast cells. For the case of starting with 125 billion yeast cells and 15% loss per month you have a value of 87.50 billion yeast cells. The percentage difference between 87.50 billion yeast cells and 55.31 billion yeast cells is 58%. So as the timeframe lengthens from 1 to 2 (or more) months the percentage differential between the values of viable yeast cells that the Mr. Malty Calculator provides and the other calculations grows.

I have stated it before and I will state it again, the yeast calculator on the Mr. Malty website makes a series of conservative assumptions:

· The George Fix pitch rate value of 0.75 million cells / ml / degree Plato is grossly conservative (too large) for a new package of liquid yeast. This value is appropriate for re-pitching on yeast.
· The starting value of yeast cells (98.33 billion yeast cells) is grossly conservative. It is 27% too low.
· The viability loss value of 21% is conservative.

I will repeat again that if folks want to use the yeast calculator on the Mr. Malty website feel free to do so but to think that you are obtaining an accurate estimate from this tool that is just not the case!

Cheers!

 

@sooners3210 short answer if I were you I would crash the first starter, decant and add somewhere between 2-2.5L of fresh starter wort. Let that go on the stirplate another 24 hours and you are done. Cold crash and decant or toss it all in.

 

If you want, you can use whatever viability numbers you want in Mr. Malty. But given that overpitching is safer than underpitching, which end of the range do you think makes more sense for a default?

Right. Wyeast consistently gives you 20%-30% more yeast than they advertise. They just don't put that on the package because they are humble as well as generous. Has it occured to you that they aim for 120B-130B cells because they know a significant percentage of those cells, a significant percentage of the time, are DOA by the time they are packaged? What other business gives you a 25% bonus of good product? And what about White Labs vials?

Your example assumes that 15% loss is closer to 'normal' than 25%. Where do you get that assumption? It also assumes 125B viable cells in a fresh smack pack or vial, to which I say not bloody likely.

First, I disagree with your assertion that 0.75M/ml/Deg P is too large for 'new' yeast. But, why do you quote and argue over appropriate pitch rates, when you don't even use pitch rates yourself?

 

Not exact, but better still is to have a microscope and a hemocytometer, per a conversation with Chris White at Big Brew this year. Better to count some cells and extrapolate the total than just estimate. Not sure I am ready for that investment, though.

 

For sure. I was looking at hemocytometer chambers on line and they don't seem too outrageous at all. But how good a microscope do you need for this?

 

I agree.

I agree again, BUT.... I would say that in the absence any ability to achieve an accurate cell count, a grossly conservative estimate is the best estimate.