[S. cerevisiae]

Is this putting too much stress on half a vial, for a lager, asking it to go from about 50B to 200B in one step?

Absolutely not, if you saw how little yeast I pitch into 600ml of wort, you would would never again question pitching half of a White Labs vial into 1L of wort. 

[S. cerevisiae]

When 100 billion cells were pitched into 2 liters of 1.036 wort at 70 degrees, the result was 205 billion cells. When 100 billion cells were pitched into 4 liters of the same wort, the result was 276 billion cells.

Increasing the cell count from 100B to 205B cells requires the viable cells to double a little more than one time, which tells me that dissolved O2 was more than likely the limiting factor in this experiment.  The requirements for this method are a starter vessel that is three, preferably four or more times the volume of the starter.  Ignoring this requirement has the potential to negatively impact the results one obtains from the method.  Luckily, one gallon jugs are relatively cheap.

[TMX]

So. I pitched yesterday at about 68F around 5pm, took a quick look this morning about 7am and saw the largest krausen EVER in on of my beers.

[Philbrew]

The requirements for this method are a starter vessel that is three, preferably four or more times the volume of the starter. 
Why?  Is it the O2 available in the headspace, and cannot enriching the O2 percentage in the headspace allow one to "cheat" on the starter/vessel ratio to some degree?  I want to do 2 starters and 8L vessels are impractical and hard-to-find! (and afford!)

[TMX]

You don't need 2  8L vessels, just 2 4L vessels, or any vessel that is 3-4 times larger than the starter you want to make.

I used 2 1gallon jugs to make 2 1L starters to pitch into 10gal of wort

[Philbrew]

You don't need 2  8L vessels, just 2 4L vessels, or any vessel that is 3-4 times larger than the starter you want to make.

I used 2 1gallon jugs to make 2 1L starters to pitch into 10gal of wort

Sorry, spell checker erased an L in my post.  I wanted to say that I want to make two 2L starters (to pitch in two six gal. lager batches).  I don't have four 1 gal. jugs.

[S. cerevisiae]

Sorry, spell checker erased an L in my post.  I wanted to say that I want to make two 2L starters (to pitch in two six gal. lager batches).  I don't have four 1 gal. jugs.

Headspace is critical to achieving a proper shake.  One is attempting to turn the wort into as much foam as is humanly possible.  This method is designed to be low-tech and low-cost. 

With that said, another thing that I am attempting to dispel is the insane notion that people have to hit the cell counts provided by yeast calculators in order to have a healthy fermentation.   It is better to have 60 billion healthy, ready to go to war with the wort cells than it is to have 200 billion stressed cells that are barely clinging to life.  The difference between 60 billion cells and 200 billion cells is approximately 180 minutes of propagation time.

The maximum cell density for 2 liters of wort is roughly 400 billion cells.  The maximum cell density for 5 gallons of wort is roughly 3.8 trillion cells; hence, pitching 400 billion cells requires log(3,800 / 400) / log(2) = ~3.25 replication periods.  Pitching 200 billion cells requires log(3,800 / 200) / log(2) = ~4.25 replication periods.  The notion that one has to pitch a 2 liter starter into 5 gallons of normal gravity lager wort in order to have healthy fermentation is ludicrous.  As there is more than enough carbon (sugar is carbon bound to water) in the average batch of wort to support the growth of 3.8 trillion cells, the limiting factor is dissolved O2 because the ergosterol and unsaturated fatty acids (UFA) that are synthesized by mother cells while O2 is still in solution is shared with all of the daughter cells that are created after O2 is depleted.  Cell health declines as ergosterol and UFA reserves decline.

By pitching cells at high krausen instead of waiting until they have reached the stationary phase and prepared for starvation, we are pitching cells with non-depleted ergosterol and UFA reserves.  The difference in ergosterol and UFA reserves from pitching a yeast culture at high krausen instead of waiting until the cells enter the stationary phase results in a lower initial load being placed on dissolved O2, preserving more O2 for future generations of yeast cells. Ergosterol and UFAs make yeast cells more pliable, which, in turn, allows for the passage of nutrient and waste products through their cell walls. 

Cells with healthy ergosterol and UFA reserves are more ethanol tolerant than cells with depleted ergosterol reserves.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3274781/

"Although most organisms cannot tolerate high levels of alcohol, certain yeasts (e.g., Saccharomyces cerevisiae) are able to maintain viability in the presence of up to 15–20 vol % ethanol. Through natural and directed evolution, yeasts have developed many strategies, also known as survival factors, to deal with ethanol toxicity (1). One important survival factor is to modify plasma membrane composition by increasing the content of unsaturated lipids and ergosterol (1,2,4,5)."

The reason why yeast cells in large part stop fermenting above a certain alcohol level is because they become dehydrated causing a reduction in cell size and a loss of turgor pressure.  Ethanol is hygroscopic; hence, it draws water out of yeast cells.  A similar thing happens when we pitch yeast into high gravity wort; however, it is phenomenon known as osmotic pressure.  Osmotic pressure is the tendency of water to be drawn to the side of a semi-permeable membrane that contains the highest solute concentration.  What happens when we pitch yeast cells into high gravity wort (hypertonic environment) is that water is drawn out of the cells into the wort, which, in turn, causes cell size to decrease resulting in reduced, if not outright cessation of cellular metabolism or even cell death. 

The following paper contains images that show what happens to yeast cells when they are exposed to high gravity solutions and high alcohol levels: http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2003.tb00162.x/pdf

[narcout]

Sorry, spell checker erased an L in my post.  I wanted to say that I want to make two 2L starters (to pitch in two six gal. lager batches).  I don't have four 1 gal. jugs.

The shaking is just to aerate the starter wort.  You could always use an alternative method of aerating or oxygenating the starter and still achieve the benefits of pitching or crashing at high krausen.

[S. cerevisiae]

The shaking is just to aerate the starter wort.  You could always use an alternative method of aerating or oxygenating the starter and still achieve the benefits of pitching or crashing at high krausen.

That statement is correct.  However,  one cannot just flood the available headspace with O2 and shake when using an undersized container. That will not work anywhere near as well as using a larger container and normal automospheric levels of O2.  The media has to be able to expand into foam, which is the low-tech equivalent of bubbling air or O2 through the media.  The beauty of the low-tech method is that there is one less opportunity to infect one's starter.

[Stevie]

Mark, with this method, would an appropriate starter be possible with as little as two table spoons of thicker slurry?

[narcout]

The media has to be able to expand into foam, which is the low-tech equivalent of bubbling air or O2 through the media.

Yes, bubbling air or O2 through a diffusion stone is the alternative method I was referring to.

The maximum cell density for 5 gallons of wort is roughly 3.8 trillion cells; hence, pitching 400 billion cells requires log(3,800 / 400) / log(2) = ~3.25 replication periods.  Pitching 200 billion cells requires log(3,800 / 200) / log(2) = ~4.25 replication periods.

Do you think there is any discernible flavor impact from that extra replication period?

[S. cerevisiae]

I need to take a photo what the amount of yeast that I pitch into 600 milliliters of wort (my primary volume is 3.5 gallons), but it is a ridiculously small amount of yeast compared to what is in a White Labs vial.  You will laugh at the thought of ever thinking that half of a White Labs vial is not enough yeast to pitch into a 1L starter when you see how little yeast I pitch.

With that said, if my math is not failing me, 2 tablespoons is just shy of 30ml. Thirty milliliters of truly thick slurry can have up to 3 billion yeast cells per milliliter, or up 90 billion yeast cells in total.  I kid you not when I say that you can pitch five gallons of ale with 90 billion fresh viable cells with no off-flavors or loss of attenuation as long as the wort is properly aerated.

[S. cerevisiae]

Do you think there is any discernible flavor impact from that extra replication period?

With proper aeration, one should not experience any discernible flavor impact from a single replication period. 

With that said, one should experience a discernible flavor impact from pitching at high krausen; namely, a cleaner tasting product.

[TMX]

If it were me, and I needed 2x2l starters, I would just order 4x1gallon jugs. I am sure you could divide the WL or Wyeast vial by 4 and still have enough yeast to make the starters.

Mark, if I am wrong here please jump in.

FWIW, these appears to be the best start to a ferment I have ever had.  The only change I wold make, is to start my starter the night prior and not 2 nights prior. I made my starters Friday night and by Sat moring they were crashing. Next time, I will start them the night prior to brewday, as most of the time I pitch around 5pm in the evening.

I ferment 10-11 gallons of wort in a 16g container, I ahve never needed a blow off tube with that much head space, when I checked this moring, the Krausen ring was within 1/2 inch of the airlock......

T

[narcout]

The following paper contains images that show what happens to yeast cells when they are exposed to high gravity solutions and high alcohol levels: http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2003.tb00162.x/pdf

That was an interesting read.  Did you see this part at the end?

"Yeast cells in the exponential phase had weak turgor pressure compared to turgor pressure of stationary phase yeast cells."

"Both groups postulated that the ability of a yeast strain to support a higher gradient of osmotic pressure could be due to turgor pressure and thickness of the cell membrane. Cells, which normally have high turgor, have membranes with higher tensile strength. Thus, stationary phase cells, which have been reported to be more stress tolerant than actively growing exponential phase cells, must have a more rigid cell membrane in order to maintain the same volume than exponential cells."