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.
“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
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.
Mark, with this method, would an appropriate starter be possible with as little as two table spoons of thicker slurry?
Yes, bubbling air or O2 through a diffusion stone is the alternative method I was referring to.
Do you think there is any discernible flavor impact from that extra replication period?
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.
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.
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
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.”
I have mentioned that yeast cells undergo morphological changes at the end of fermentation in preparation for hard times in several thread on this forum and others.
https://www.homebrewersassociation.org/forum/index.php?topic=21705.msg275241#msg275241
“By stepping a culture at the end of the exponential phase, we are pitching yeast cells that require very little in the way of replenishment. Hence, we will experience a shorter lag phase than we will if we pitch a culture that has reached quiescence because a quiescent culture has to undo the morphological changes it underwent in preparation for hard times. A quiescent culture also has to replenish the ergosterol and UFA reserves that were spent post-exponential phase, which increases dissolved O2 requirements.”
https://www.homebrewersassociation.org/forum/index.php?topic=21952.msg279097#msg279097
“As I have mentioned many times, a high krausen pitch will always outperform a “fermented out” pitch because the cells are in peak health and do not have to undo the morphological changes that occur at the end of fermentation. Add in sufficient aeration and a strain with a high attenuation rate, and an AA of 85% is not out of the question.”
I have also mentioned that cell wall thickening is the major morphological change.
https://www.homebrewersassociation.org/forum/index.php?topic=20692.msg262969#msg262969
“At the end of fermentation, yeast cells go into survival mode where their cell walls thicken and they store carbohydrate as glycogen. In effect, the cells are preparing for hard times. It takes longer to exit this state than its does when the yeast cells are still in active growth mode; hence, lag times in addition to oxygen demands are also increased.”
What the authors did not mention is that this survival mechanism has to be undone during the lag phase; otherwise, nutrients and waste products cannot easily pass through the cell wall and plasma membrane. Hence, stationary phase cells are no more likely to survive the lag phase than yeast cells that are pitched during the exponential phase, which is why we pitch at a higher rate.
OK, light bulbs are turning on all over. “as much foam as is humanly possible” makes big time sense because foam has huge surface area.
This engineer has always believed that “low-tech and low-cost” are the better solution.
I have trouble trusting the yeast calculators that call for incredibly huge pitching rates without factoring in the state of yeast vitality.
Thanks, Mark. Very enlightening post on how yeast do their thing.
What I hadn’t heard before was the part about stationary cells being reported to be more stress tolerant.
I haven’t had a chance to read the article cited at the end of that sentence, but here’s the link. I have no idea if it’s interesting or presents anything that you haven’t already mentioned. My guess is that you’ve probably read it before.
For what it’s worth, I believe the Mr. Malty calculator uses the fairly standard rate of .75 million cells per milliliter of wort per degree Plato (and twice that for lagers).
I’m not saying that’s the be all and end all of pitching rates or that it isn’t worth experimenting with different rates for different styles of beer, but it’s not like Jamil just arbitrarily made it up.
The morphological changes occur in order to harden the cells against the harsh reality of living in a toxic, low-nutrient medium for an unknown amount of time.
Cell count is only half of the equation. Cell health is equally, if not more important. When pitching cells at high krausen, one is pitching very healthy cells with very pliable cell walls that require little to no maintenance before they can go to work; therefore, reducing lag time. The number one bogeyman with normal gravity fermentation is house infection. Shortening the lag phase shortens the time that bacteria have to multiply (as does reducing the number of replication periods), and bacteria multiply three times faster than yeast. These growth rates are what we are up against in a real world brewery.
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg277460#msg277460
"A small amount of bacteria can overtake a much larger amount of yeast because the bacteria cell population increases 8-fold every time the yeast cell population doubles. If we were to normalize the propagation period between yeast and bacteria (bacteria multiplies three times faster than yeast), the growth equations would be:
yeast_cell_count = initial_cell_count * 2n, where n = elapsed time in minutes since the end of the lag phase / 90
bacteria_cell_count = initial_cell_count * 8n, where n = elapsed time in minutes since the end of the lag phase / 90
If we run the numbers, it should become crystal clear why one wants to pitch a large, healthy yeast culture while doing everything possible to minimize the opportunity for bacteria to catch a ride into one’s yeast crop, starter, or fermentation vessel. It should also become clear why the growth phase is called the exponential phase.
Cell counts at 90 minutes
yeast_cell_count = initial_yeast_cell_count * 21 = initial_cell_count * 2
bacteria_cell_count = initial_bacteria_cell_count * 81 = initial_cell_count * 8
Cell counts at 180 minutes
yeast_cell_count = initial_yeast_cell_count * 22 = initial_cell_count * 4
bacteria_cell_count = initial_bacteria_cell_count * 82 = initial_cell_count * 64
Cell counts at 270 minutes
yeast_cell_count = initial_yeast_cell_count * 23 = initial_cell_count * 8
bacteria_cell_count = initial_bacteria_cell_count * 83 = initial_cell_count * 512
Cell counts at 360 minutes
yeast_cell_count = initial_yeast_cell_count * 24 = initial_cell_count * 16
bacteria_cell_count = initial_bacteria_cell_count * 84 = initial_cell_count * 4096
Cell counts at 450 minutes
yeast_cell_count = initial_yeast_cell_count * 25 = initial_cell_count * 32
bacteria_cell_count = initial_bacteria_cell_count * 85 = initial_cell_count * 32768
Cell counts at 540 minutes
yeast_cell_count = initial_yeast_cell_count * 26 = initial_cell_count * 64
bacteria_cell_count = initial_bacteria_cell_count * 86 = initial_cell_count * 262,144
Cell counts at 630 minutes
yeast_cell_count = initial_yeast_cell_count * 27 = initial_cell_count * 128
bacteria_cell_count = initial_bacteria_cell_count * 87 = initial_cell_count * 2,097,152
Cell counts at 720 minutes
yeast_cell_count = initial_yeast_cell_count * 28 = initial_cell_count * 256
bacteria_cell_count = initial_bacteria_cell_count * 88 = initial_cell_count * 16,777,216"
Exactly!
For what it’s worth, I believe the Mr. Malty calculator uses the fairly standard rate of .75 million cells per milliliter of wort per degree Plato (and twice that for lagers).
I’m not saying that’s the be all and end all of pitching rates or that it isn’t worth experimenting with different rates for different styles of beer, but it’s not like Jamil just arbitrarily made it up.
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Sorry, I didn’t mean to infer that the Mr. Malty calculator is inaccurate. In fact it’s probably the best. It’s just that all the yeast calculators seem to be overly cautious on yeast production rates except for stir plates. I realize that it would be difficult to add to the calculator the Shake-it-until-it’s-all-foam method or combine O2 at start plus shaking. But, as it is, the calculators tend to push one into buying a stir plate, especially if you want to do lagers or big beers. I want to brew lagers and the $200 for a heavy duty stir plate and 5L flask could be better spent on a wort chiller or a temp controller for my fridge and an upgrade of my brew pot.
Sorry, I didn’t mean to infer that the Mr. Malty calculator is inaccurate. In fact it’s probably the best. It’s just that all the yeast calculators seem to be overly cautious on yeast production rates except for stir plates. I realize that it would be difficult to add to the calculator the Shake-it-until-it’s-all-foam method or combine O2 at start plus shaking. But, as it is, the calculators tend to push one into buying a stir plate, especially if you want to do lagers or big beers. I want to brew lagers and the $200 for a heavy duty stir plate and 5L flask could be better spent on a wort chiller or a temp controller for my fridge and an upgrade of my brew pot.
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on uline.com, you can get a 4 pack of 1 gallon glass jugs for less than $20 (plus shipping), split a single vile 4 ways, and have a 1 gallon starter…no stirplate needed.
T
Just remember to shake the jugs like they owe you money (think mafia enforcer)! 
Yes, that could very well be true (or perhaps they are overly optimistic on the effects of stir plates).
I believe at least some of the predicted results from the Mr. Malty calculator are based on real world observations, but I do not know to what extent (though this info may be out there on the internet somewhere).
Fortunately, as has been pointed out, you do not need to be exact in your pitching rates. They are just another tool that you can use to achieve your intended flavor profile.
By the way, another good source for inexpensive one gallon glass jugs is your local supermarket (and they come filled with delicious juice).
Yup, that’s my plan. Hmmm…I wonder if my local Ace Hardware would let me put them on their paint shaker? 