Yeast cell count?

[Peteyb]

Hi all,

Bit of a simple question. I've just got some omega yeast OYL-090 espe kviek and I cant find the cell count per ml any where! I'm going to assume its 100 billion in the pack.
If anyone knows that would be great

Cheers

 

[foxbat]

There's 150bn in the Omega ale and lager packs on the date of packaging. I'm assuming Kveik is no different.

 

[Peteyb]

I did think something that said there is 150B cells.
Made me starter at 4 and still have 0 activity

 

[foxbat]

@BeerCat knows all about Kveik. He might be able to offer some advice.

 

[Joust]

What difference does it make to the brewing, out of interest?

 

[BeerCat]

@BeerCat knows all about Kveik. He might be able to offer some advice.

Sorry only really familiar with the farmhouse strains apart from Juggernaut and i probably overpitch all my beers. I do tend to pitch active kveik starters if i can but if your pitching warm a teaspoon seems to be a popular choice for bringing out esters.

 

[saccharomyces]

There is no need to make a starter with 150B cells other than to wake the culture up. The maximum cell density for a 1L starter is approximately 200B cells. One hundred and fifty billions cells gives on a pitching rate of 6.5 million cells per milliliter. That cell count will get the job done in 23L of wort.

What a lot of brewers do not understand is that the yeast biomass does not grow Iinearly. It grows exponentially at the rate of 2^n, where "n" is the number of replication periods and the symbol "^" denotes raised to the power of. The reason for this growth pattern is the every cell buds a daughter cell every replication period. The number of replication periods required for a yeast culture to reach maximum cell density is the log base 2 of the maximum cell density for the batch of wort divided by the pitched cell count. Most calculators do not support the log base 2 function, but that can be calculated using either the natural log function "ln" or the log base 10 function. I will use the log base 10 function.


number_of_replication_periods = log(maximum_cell_density_for_batch / pitch_cell_count) / log(2)

Let's calculate the maximum cell density for a 23L batch.

maximum_cell_density_for_1L = 200,000,000,000 (200 billion cells)
maximum_cell_density_for_batch = volume_in_liters * maximum_cell_density_for_1L
maximum_cell_density_for_batch = 23 * 200,000,000,000 = 4,600,000,000,000 (4.6 trillion cells)

Starting with 200 billions cells, our culture will go through

number_of_replication_periods = log(4,600,000,000,000 / 200,000,000,000) / log(2) = 4.52

What this figure means in layman's terms is that the yeast culture will double in size 4.52 times after it exits the lag stage before it cannot grow any larger.

Starting with 150 billions cells, our culture will go through

number_of_replication_periods = log(4,600,000,000,000 / 150,000,000,000) / log(2) = 4.9

What this figure means in layman's terms is that the yeast culture will double in size 4.9 times after it exits the lag stage before it cannot grow any larger.

As one can see, there is very little difference in the amount of time a culture remains in the exponential growth phase between 150B and 200B cells. It is not even an extra replication period. Even if we pitch 100B cells, we only looking at one additional replication period for a yeast culture to reach maximum cell density in a batch of wort.

number_of_replication_periods = log(4,600,000,000,000 / 100,000,000,000) / log(2) = 5.52

Here, my friends, is why I always state that yeast cultures are like nuclear weapons in that one only needs to get reasonably close to one's target cell count. As long as there is enough dissolved O2 to sustain the grown, it does not matter if we underpitch by as much as 50%. We could theoretically pitch 1/4th of the necessary cell count if we have enough dissolved O2 and our sanitation is on point. The main reason we need to be close to our desired cell count is because the bacteria cell count grows by a factor of eight every time the yeast cell count doubles. I cover all of this information in detail in my blog entry entitled "Yeast Cultures are Like Nuclear Weapons" (Yeast Cultures are Like Nuclear Weapons | Experimental Homebrewing).

 

[Drunkula]

@saccharomyces How many yeast cells die or become damaged during reproduction. You've done all the maths but it's a bit like the thing where the world would be three metres deep in dead flies after one summer if they didn't encounter hazards.

And homebrewers typically don't aerate anywhere near enough, or give a second dose of oxygen the next day which some breweries do.

I've seen in posts you saying that yeast growth calculators don't use the n^2 growth model. Maybe there's a reason for that.

 

[saccharomyces]

On a stir plate? Many, one can bet on significant cell death occurring on a stir plate that is spun fast enough to aerate the wort. Shear stress takes a toll on yeast cells and the spinning stir bar is source of shear stress. Shaken, not Stirred (SNS) works on a very different principle, one that makes use physics. Yeast cells do not need to be spun. They need O2 and they need it during the lag phase. SNS takes advantage of the fact that foam has significantly more specific surface area than a liquid to air interface. The more specific surface area, the more O2 can be diffused. It is simple physics. SNS also takes advantage of a commonly accepted propagation practice; namely, stepping at high krausen. Stepping at high krausen saves ergosterol and unsaturated fatty acid reserves that would be wasted if the culture were to be allowed to ferment out with the cells entering quiescence.

If you have never tried SNS, you need a container with a screw cap that is at least four times the volume of the starter. The boiled and cooled starter wort is added to the container after it has been sanitized. The cap is then screwed down tightly on the container, and the container is shaken like if owes one money. The goal is to turn as much of the starter wort into foam as is humanly possible. The cap is then removed from the container, so that the culture can be pitched. The cap is screwed back on and the container shaken much more gently to disperse the cells before the cap loosened to allow CO2 to escape. The starter should reach high krausen within 12 hours for a 1 or 2L starter. It may take up to 18 hours, but that is a rarity. If one is not going to be ready to pitch the starter within 12 hours, one should place it in one's refrigerator after signs of low krausen appear. That move will retard the fermentation, giving one more time to finish brewing. The culture should be removed from the refrigerator at least two hours before it needs to be pitched. I have yet to see anyone go back to using a stir plate after using SNS. Most brewers are astonished to learn that making a high quality starter can be that simple.

Here's is Denny Conn's first experience with the technique: Old Dog...New Tricks | Experimental Homebrewing

Continuing, White Labs claims that their PurePitch packages contain 100B cells. What that means is that one can pitch a very fresh package into 23L of well-aerated wort under 1.060 gravity without making a starter, that is, if the culture has been handled well in transit from White Labs. Instead, we can take a conservative approach and limit the viable cell count to 50B cells for starter purposes. Even at 50B cells, a yeast culture only has to double two times in order to reach maximum cell density in 1L of 10% w/v wort. Regardless of what the yeast calculator writers claim, the yeast biomass grows at a rate of 2^n, where n is the number of elapsed replication periods and the symbol "^" denotes raised to the power. Anyone who claims otherwise does not know a thing about yeast or microbiology. Every yeast cell that is alive during a replication period buds a daughter cell. After the first replication period, we have two times the initial cell count. During the next replication period, every cell that is alive buds a daughter cell, which means that we now have four times the initial cell count. During the next replication period the yeast biomass will double again and so forth. Effectively, the cell count multipliers are 2, 4, 8, 16, 32, 64, 128, 256 .... That, my friend, is a 2^n growth pattern. The do not refer to the growth phase as the exponential growth phase (a.k.a. log phase) for no reason at all.

Inadequate aeration is a problem for many amateur brewers. However, it does not take much to air saturate wort. Inserting a simple venturi into one's kettle drain tubing is all that is needed. I use this simple venturi design. It is attached to the end of the tubing that drain's one's kettle and held vertical down inside of one my fermentation vessels.

When using this venturi design, one will need a fermentation vessel with quite a bit of headroom or one is going to have to stop the flow and wait for the foam to subside before proceeding. Whenever wort is foaming, it is picking up O2.

With respect to aeration on the second day of fermentation, Brian Kirsop wrote a seminal paper on oxygen in brewery fermentation (https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.2050-0416.1974.tb03614.x ). In that paper, he classified yeast cultures as belonging to one of four classes with result to oxygen demand.

Class O1 - yeast cultures with O2 demands that can be satisfied with half-air saturated wort (4ppm)
Class O2 - yeast cultures with O2 demands that can be satisfied with air saturated wort (8ppm)
Class O3 - yeast cultures with O2 demands that can be satisfied with pure O2 wort (20ppm)
Class O4 - yeast cultures with O2 demands that cannot be satisfied with pure O2 saturated wort


The reality is that most of the cultures available via the home brew trade fall into classes O1 and O2 because high O2 demand cultures do not last due to being more difficult to use. We do not start to see strains with high O2 demand until we look at the Yorkshire square cultures. Most, but not all, of the square-type cultures are Class O3 or Class O4 with respect to oxygen demand. That is why most of the Yorkshire square/round breweries have fermentation vessels that are equipped with fishtail spreaders.




 

[Drunkula]

@saccharomyces are there any qualitative results? The plural of anecdote isn't data.

 

[saccharomyces]

All one needs to do is use Google. There are a million publications with respect to yeast biomass growth. I am not making this stuff up.

Let's start with page that covers the yeast growth phases that was written by biology professor: 4.3: Yeast growth phases


I you are challenging my assertion that yeast calculators close to useless. Well, that is based on science as well. What is the correct pitching rate? Well, it can be all over the place based on the genetics of the yeast being pitched, especially when considering that different yeast culture can have different O2 demands. Yeast calculators attempt to turn something that is science into a math problem. It does not work that way. My B.Sc. and M.Sc. degrees are actually in computer science and engineering. I have been a practicing computer scientist and engineer for over 40 years. I have been a amatuer brewer and amateur brewing scientist for almost thirty years. During my career, I have modeled many things. Not everything is that easy to model.

The reality is that the range of cell counts that will get the job done is much larger than the yeast calculators would lead one to believe when we are talking about gravities below 1.080. High gravity brewing is another story because it is very stressful on yeast cells due high osmotic pressure, which draws water from inside the cells to the wort side of the cell plasma membrane, resulting a loss of turgor pressure and eventually cell implosion. That combined with the increased difficulty of dissolving O2 in high gravity wort is the reason for the higher pitch count. It is higher because of premature cell death and the fact the lower dissolved O2 in high gravity will not support as many replication periods as higher dissolved O2 in lower gravity wort.

The TL;DR version is the minimum cell count required for fermentation is 100% based on yeast strain genetics and wort gravity. Anyone who attempts to turn it into a simple formula is going to be wrong most of the time. The only thing that will tell a brewer what is the minimum number of cells needed to ferment a batch of wort is experience with a strain in one's brewery. Every brewery on the planet places selective pressure on its yeast culture, which results in genetic drift from the original. Often the genetic drift is an improvment in fermentation characteristics from the original.

One last thing and I am done because it does not appear that you can be convinced. I do not know of a single brewery in the United States other than the Alan Pugsley install Peter Austin and Partners systems that aerates fermenting wort on the second day (the Peter Austin and Partners breweries use Ringwood, which is a high O2 Yorkshire culture that Peter acquired from the Hull Brewery). If a brewery has to aerate wort after fermentation has begun in order to complete fermentation without stalling, especially at the low gravities that dominate British brewing, then odds are that they are using a high oxygen demand Class O3 or Class O4 yeast strain.

 

[Drunkula]

You could have just said no, I don't have any data.

Goodbye.

 

[Bill_g]

Sacharomyces, please don't give up on us! I for one, have thoroughly enjoyed reading your replies & referred articles. Thank you for attempting to bring some science into the subject, something often lacking on this forum. I want to remain positive so I won't labour this point, but I'd rather read long replies from someone who demonstrates an extensive knowledge of the topic rather than short one liners from those who have little to add.
I think it's fair to say that your arguments are based on solid logical application of the science and good empirical results rather than laboratory grade cell counts etc, but to my mind you at least show an interesting alternative approach and a sound basis for experimentation.

 

[saccharomyces]

Biil_g, I appreciate you kinds words. I am not here to stroke my ego. A lot of what I post goes against amateur brewing (a.k.a. homebrewing) dogma. I started brewing 28 years ago. Back then, Brits were light years ahead of us. Pretty much all of our kit beers, extract, and dry yeast came from the UK (does anyone remember EDME's Bruce's Dogbolter?). However, the big difference in the U.S. was that those who go entered the hobby were from the upper middle/professional class, which means that there was significantly more money to be had by enterprising souls in the U.S. than the UK. It took many years for homebrewing to catch on with the working class here in the U.S. because they were mostly happy with NAIL (North American Industrial Lager) beers. The beer you guys took for granted was considered to be premium beer in the United States. I got involved in amateur brewing after visiting the Wild Goose Brewery in Cambridge, Maryland. That brewery was 20bbl replica of the Ringwood Brewery in Hampshire, England. I like to hang out on the British brewing sites because unlike most of my American brethren, I enjoy British-style brewing.

 

[LeeH]

One day I’ll sit down and count them to make sure I’m not getting ripped off.

 

[johncrobinson]

Hi Saccharomces,
Found your concepts most interesting,

Could you please post some info on the venturi in your picture, and if its home made how to construct it.Much appreciated.

 

[Peteyb]

You guys are amazing, thanks alot for all your replies