After replication period 2, the yeast biomass has quadrupled in size. That difference means that after replication period 1, the yeast biomass has doubled in size. The reality is that the cell count is closer to 2^N times the original cell count, where N is the number of replication periods that have elapsed and the symbol ?^? denotes raised to the power of. While I may be wrong, I believe that the confusion stems from brewers believing that the yeast biomass grows linearly, that is, the number of cells at replication period N is N times the original cell count. Lag times and dissolved O2 demands are not significantly reduced until the one pitches in excess of 800 billion cells per 5 gallons of wort. The difference between 200 billion cells and 400 billion cells is also insignificant in the grand scheme of things.

The difference between 200 billion cells and 300 billion cells is insignificant. Let?s examine the first misunderstanding when it comes to yeast cell counts. People have been so focused on cell counts since Kai Troester published his experiments with different stir plate protocols that the forest has been lost for trees. I even wrote a blog entry about the amateur brewing community?s preoccupation with cell counts entitled ?Yeast Cultures are Like Nuclear Weapons? back in 2015 (somehow the publication date got changed when I performed a few edits on the text recently).

I have been stating that close is more than good enough when it comes to cell counts for years. YEAST CELL COUNT AND WHY STARTERS MAY NOT BE NECESSARY Saccharomyces introduced a starter method called Shaken Not Stirred which relies more on a smaller number of yeast cells at their peak of health rather than a large number many of which are old and tired by the time they are pitched. Cerevisiae on various homebrew forums I have stopped worrying about cell count. Cheers!Īfter reading posts by Saccharomyces aka Yeast Whisper aka S. I hope to see Chris White at HBC and have this conversation with him. I wonder how/if this will impact viability. Further, this will be their standard packaging density in the future, but they're also going to make the packages slightly larger to account for this. Of course one must account for this discrepancy in the starter calculation.

So a 40 mL PP has only 86B cells, not the 100B claim. Their PP claims 'Made to contain over 100 billion cells.' Yet checking the QA report for the vial I have on, instead of an actual cell count, it says it's made to contain 2.15M cells/mL. What I didn't know is if someone has independently assessed WL's PP packaging viability and that accounts for the higher viability rates in BS3 compared to say, Brewer's Friend's calculator (which is using data from 2012, predating PP).Īll this stems from a conversation I had with WL yesterday around their cell counts and package labelling. I'm aware of the impact of packaging, among other variables, impact on viability. Their new packaging probably negates anything tested in the prior packaging in terms of viability and total cell counts. I cannot comment too much on White Labs other than to say the two tubes I tested back a number of years ago were just a bit over the 100 billion total cells. This correlates fairly well with the information I was able to squeeze out of the Wyeast people at HBC back in 2019. Most clock in at a consistent count of 108 billion to 112 billion cells total (counting both dead and live cells). I use yeast packages as a means of calibration on my cell counting technique and personally, I have never had a Wyeast package check in at less than 100 billion active cells even at 4 to 6 months old. This is one reason that some of the yeast companies have switched from printing the manufacture date to printing the best-by date on the packages. The rate of decrease in viable cells over the age of the yeast package tends to be extremely conservative in the estimate of % viability, so the actual percentage of viable cells will tend to be greater than the models predict. Then you get into the models which have mostly been developed decades ago and do not take into account the improvements which have been made in yeast health, packaging integrity, and overall vitality of the yeast over the past number of years. There is a pretty wide range of cell counts which the yeast can and will perform consistently and that is highly strain dependent as well. It is never perfect, but designed to get you in the ballpark. The accuracy of the model is highly dependent upon the age of the yeast package, the conditions under which it was stored, actual viable yeast at packaging, yeast strain, etc.

Beersmith 3 yeast