yeast starter

I have entered a recipe for a dunkelweizen and using dry yeast.  The suggestion by the software is 2 packs.  When I try to plug in using a starter and stir plate with the one pack, I get the same reading on the result of cell producted no matter the size of the starter (in liters).  why does that happen.  i am starting with 147 bil cells and need 256 billion. 

BeerSmith is wrong. Use mrmalty.com or yeastcalc.com. 

Hi,
  For dry yeast, you may have noticed that the calculation is shown with no starter.  In general dry yeast does not require a starter at all - only hydration and sufficient yeast.  I believe even the Mr Malty calculator shows dry yeast packet calculations with no starter.  That is why changing the size of the starter does not change the yeast requirements.

Brad

tom_hampton said:

BeerSmith is wrong. Use mrmalty.com or yeastcalc.com. 

Click to expand...

Source?

http://www.beersmith.com/forum/index.php/topic,5895.15.html

I think Tom refers to this "debate" to which I'd like to see the actual formulas used in each, if someone knows them for certain. 

Logically, either one formula is just wrong, which seems improbable to me, or it's two different approaches, which I posted as a possibility, and no one said whether I was grossly wrong. 

To me, having a user-defined "growth factor" makes little sense for most people.  How would I use or set that?  It seems more logical to embed the actual known/estimated growth rates for simple, shaken, stir plate, etc., and have the tool figure out the number of cells that will happen given the method used.  Brewers typically use full packages and one method, so those two are usually fixed.  The package viability (based on age) and the starter method are the "variables" but their factors are generally agreed upon. 

Volume of starter fluid, beginning number of cells less viability lost, times growth factor of method...................what else is there?

Lol thats not a source! By the way did you see the last post on there from me?

Madspoiler...  I saw your posts, but I'm in new Zealand on work. I'll reply when I get back to the srates.

Not trying to throw salt on this, but why is there such a disparity between the viability calculation in BS2 vs. YeastCalc and Mrmalty?

Example: I enter a Package Date of 07/28/12 into BS2 and it tells me the viability is 89.45% while YeastCalc says it's 77%, and Mrmalty says it's 78%.

Interestingly enough; all 3 are pretty close in the number of cells required for a particular OG (1.065, in this case) - BS2 says I need 234.2B, YeastCalc says 237B, and Mrmalty says I'll need 236B so it would seem the formulas used in those calculations are consistent across the board, so why are the viability calculations so different?

Thats the kinda stuff were all talking about and wondering. Seeing contradictory information makes you less confident in your brew day. I dont think anyone cares which one is right or wrong, just what one should we be using and if there is a problem with the way BS is figuring things than it should be changed.

philm63 said:

Example: I enter a Package Date of 07/28/12 into BS2 and it tells me the viability is 89.45% while YeastCalc says it's 77%, and Mrmalty says it's 78%.

Click to expand...

This is interesting partially b/c it reminded me of something I read in an old Zymurgy magazine (mid-1980s) about big differences in viability between Wyeast and White.  Something about the White tubes being less favorable to yeast health. 

So I wonder if there is a standard yeast viability across the industry, or do Wyeast and White use their own numbers based on their own products? 

That's exactly what I'm looking for; a standardized viability factor. With that, it seems to me all 3 calculators would pretty much agree.

I played around with the calculator in BS2 today in an effort to dial-in the pitch for an upcoming IPA and to get the viability between BS2 to match that of Yeastcalc, I had to set the package date back in BS2 tricking it into thinking I had an older batch of yeast.

While this brought the viability in-line with the other calculator, BS2 still told me I needed only a 1.3L starter on my stir plate, when the other guys are telling me I need around 2L. So even with consistent viability numbers in each calculator, I now get very different volumes. And yes; stir plate is selected in every case.

So which is it? Do I go with Yeastcalc and use a full 2L or BS2 and go with 1.3L? Should I split the uprights and roll the dice?

HELP!

This is starting to sound like the different hops utilization models to me.  Same general concept, similar variables (AA%, gravity, time) with different assumptions about extraction leading to different forecasts of the IBUs.  I would assume that only Wye and White have done the research to chart the decline in viability, so I imagine that all calcs use one of their loss assumptions.  No idea if they use the save data/curve. 

The two issues that bug me the most are 1) assuming that typical brewers use anything other than a full package to start with, and 2) allowing me to set a "growth factor" like I can control that somehow.  Seems like I would choose the method (stir-plate) and the calculator would pump out the math based on starting with 100 billion, less viability loss, times stir-plate, on XX volume of YY gravity wort.    If I need more, I do it bigger or I do it twice.