[Joe Sr.]

Thanks for writing up your experience Denny.

I just might have to give this a try me self.

[S. cerevisiae]

Just a guess here, if you inoculate post shake, might you miss out on some of the surface area contact that is supposed to be one of the benefits?

I'm guessing that pre-shake inoculation means there are yeast cells happily replicating in the foam.

Yes, I do believe that the cells may pick up more O₂ during shaking, but there has to be cost.  The $10,000 question is, how big is that cost?  I do not have enough data points to draw a solid conclusion.  What I do know at this point is that the method has been replicated by enough people to know that it is not a fluke.

[kramerog]

Foam only when shaking, not during the "regular" fermentation, which I assume is what you mean by "incubation".  And it's not nearly as much foam as what I see in your picture.

Turning the medium into mostly foam is the key to this method. If you are not producing at least as much foam as can be seen in the photo above, then you are not shaking vigorously and/or long enough.  I literally screw the cap down tight, and shake the vessel vertically as vigorously as I can for one minute.  A lot of people attempt the method with a solid rubber stopper, but a screw on cap is really not an option with the method.  One literally has to shake the starter like one is attempting to collect money from it for the mafia.  One of the British brewers that I know from another forum wins the prize for shaking.  He managed to turn media almost completely into foam.  That feat requires a massive amount of shaking.

I've been ruminating about this technique and here are my ruminations.  Turning the wort into mostly foam isn't necessary to achieve 99% of saturation based on what I have read elsewhere.  Specifically, swirling a carboy for 40 seconds is enough to saturate wort with oxygen according to various reports and that produces very little foam.  So what does turning the wort into foam do?  I think if you don't pitch yeast first then the answer is basically nothing; the wort is fully aerated but you could have gotten the same result without a workout. 

So let's assume that pitching the yeast into the starter wort and then shaking the starter is key.  If nothing happens while the yeast is contained in the foam then all you got yourself is some shear-stressed yeast,  wort at saturation and a sweaty brewer.  So now you've wasted your energy and damaged your yeast.

So let's assume that something happens while the yeast is suspended in the foam.  Is it possible that the yeast can work fast enough to deplete the dissolved oxygen in the starter  and that oxygen in the bubbles transfers into the wort and into the yeast before the foam entirely collapses but that this oxygen transfer is minimal without foam?  In other words, shaken not stirred has the benefit of making a starter with pure oxygen, without the technology and cost?

What are your thoughts on why the vigorous shaking is key?

[S. cerevisiae]

I've been ruminating about this technique and here are my ruminations.  Turning the wort into mostly foam isn't necessary to achieve 99% of saturation based on what I have read elsewhere.  Specifically, swirling a carboy for 40 seconds is enough to saturate wort with oxygen according to various reports and that produces very little foam.

Remember what I mentioned earlier about the tendency of American home brewers to make easy things hard and oversimplify hard things?  Here's one of the areas where American home brewers attempt to oversimplify a hard thing.

There's no way that 40 seconds of swirling fully saturates a 5-gallon carboy full of wort. Whoever made that claim was absent the day that they taught partial pressures in thermodynamics.  There is not enough surface area, nor is there enough gas for saturation to occur in 40 seconds.  There had to O₂ pickup during the transfer.  Once again, a gas dissolves into a liquid at the interface between the gas and the liquid.  Surface area is critical to the process.

What are your thoughts on why the vigorous shaking is key?

There is no magic bullet.  The method merely takes advantage of physics to maximize dissolved O₂ in a low tech way.  While the cells that are on the surface of the thin layers of liquid that form the bubbles are subjected to 21% O₂, does that O₂ pickup impact growth?  I do not have enough data points to draw a conclusion.  Here's what I do know, brewing yeast cells only need three things to grow: carbon (sugar is carbon bound to water; hence, the term carbohydrate), space, and enough O₂ to support cellular health.  They do not need to be stirred during propagation because most brewing strains exhibit NewFlo flocculation; hence, they will not clump (floc) or sediment until glucose, mannose, maltose, sucrose, and maltotriose have reached genetically set levels, which are on the other side of high krausen.  Having fully air saturated wort from the start makes it easier for the mother cells to replenish their ergosterol and unsaturated fatty acid reserves early on (the same thing occurs when we diffuse pure O₂ before pitching).  A mother cell with full ergosterol and UFA reserves is a healthy cell. A mother cell shares her ergosterol and UFA reserves with all of her daughters. The fuller her reserves, the fuller her daughter cell's reserves and her daughter's daughter's cells, and so forth.   Ergosterol and UFAs make the cell plasma membrane more pliable, which makes it easier for nutrients to pass into and waste products to exit the cell.  In effect, ergosterol and UFA levels affect a cell's ability to utilize carbon for energy.

[kramerog]

Thanks for your thoughts.  I've always been skeptical of the 40 second swirling thing so while I do it I also aerate while racking.

[macbrews]

So could there be an advantage in this technique if you added pure O2 to the wort via a stone, or to the deadspace prior to shaking, or would that be unnecessary?

[denny]

To me, and this is the reason I tried Mark's procedure, it comes down to what's the difference between the theoretical ideal and the practical reality?  I've always said to Mark that while his methods were undoubtedly the best way to do it, I didn't think that there would be any difference in real life.  I decided it was time to find out for sure.  I would say to all of you who are posting theories about why it will or won't work, TRY IT for yourself and post your results.  That's the way citizen science works.  We need more than just a few data points.  And a big thanks to Mark (and Marshall and all the other experimenters) who make us all think and re-evaluate what we think we know.

[S. cerevisiae]

So could there be an advantage in this technique if you added pure O2 to the wort via a stone, or to the deadspace prior to shaking, or would that be unnecessary?

One does not need to shake if one uses pure O₂.  Oxygen from air saturates at 8ppm at room temperature.  Pure O₂ saturates at 40ppm, which is almost double the amount of O₂ that would be available to the cells if they were growing in air.

With that said, this technique is best suited to the propagation of class O1 (4ppm dissolved O₂) and class O2 (8ppm dissolved O₂) strains (from my experience, most of the strains available to home brewers fall into either class O1 or class O2 when it comes to O₂ demand).  I recently propagated a class O3 (40ppm)/class O4 (>40ppm) yeast strain (NCYC 1333), and its O₂ demand pushed the outside of the envelope.  What that said, the strain did achieve over 80% apparent attenuation with open fermentation, so I may be wrong.

[klickitat jim]

So could there be an advantage in this technique if you added pure O2 to the wort via a stone, or to the deadspace prior to shaking, or would that be unnecessary?

It's what I do. 30 seconds O2, shake a little

[Wort-H.O.G.]

so Mark- I have a stir plate with 5 speed settings. i stopped creating a vortex by lowering speed so that the wort was just circulating but no vortex. i leave it on for about 8-12hrs then shut it down and when high krausen, then if ready pitch or put in fridge until im ready.

without vortex, would this facilitate good culture growth without shear stress?

[S. cerevisiae]

without vortex, would this facilitate good culture growth without shear stress?

Shear stress is placed on the cells as long as there is turbulent flow.  Lowering the stir speed just reduces the level of shear stress that cells constantly have to endure.  Lowering the stir speed will lower the amount of O₂ that gets dissolved before the culture starts to outgas (O₂ does not enter the flask after the culture starts to outgas), which will result in poor health if one does not inject sterile air or O₂.

[dilluh98]

I think this is something that has been imprinted on the minds of brewers (myself included): that yeast propagation occurs more readily or in a more beneficial way when the solution it is in is stirred - fast or slow. From what Mark is saying about how yeast is genetically modified to stay in *suspension* until the wort dips below a threshold level of sugar, this is not the case at all. If it were, we should really be setting up giant stir plates underneath our carboys during fermentation.

** Trying to use more accurate language - I don't think yeast can ever truly be in solution.

[S. cerevisiae]

From what Mark is saying about how yeast is genetically modified to stay in *suspension* until the wort dips below a threshold level of sugar

The tendency to remain in suspension until genetically set levels of glucose, mannose, maltose, sucrose, and maltriose are reached is only exhibited by yeast strains that exhibit NewFlo flocculation.  The are Flo1 brewing strains where flocculation is inhibited by mannose, but not glucose.  NCYC 1269 is a Saccharomyces pastorianus (lager) strain that exhibits Flo1 flocculation.

NCYC 1269

Information
        Flocculent.
        Flo1 type flocculation.
        For use in Tower Continuous Fermenters.

Depositor
   Dr. R.N. Greenshields, University of Aston, Birmingham, UK.
Deposit Name
   Saccharomyces cerevisiae, Saccharomyces carlsbergensis, Sacc
Month of deposit
   March
Deposit Year
   1968
Habitat
   Lager production strain.


Hopefully, forum members noticed the comment about the NCYC 1269 being used in continuous tower fermentation.  Continuous fermentation is a very different process from how we make beer.  Tower fermenters are bioreactors that are used to ferment beer using a continuous process where beer is continuously drawn off of the top while fresh wort and O₂ are added, and yeast is recycled.  Fermentation occurs very quickly in a tower fermentation vessel.  Ales usually ferment in around 4 hours whereas lagers ferment in around 10 hours.  While exhibiting NewFlo flocculation, Whitbread "B" (a.k.a. NCYC 1026, Wyeast 1098, White Labs WLP007, and Fermentis S-04) was originally selected for use in tower fermentation vessels, which is why it is so darn flocculent.

NCYC 1026

Information
   Flocculent.
NewFlo type flocculation.
       1:5:4:5:5
       O2, DMS 33 µg/l, low acetic, high lactic, diacetyl 0.42ppm only, used commercially in Tower
       Fermenters (continuous process), non head-forming, no estery flavour. Contains 2µ plasmid.
Depositor
   British Brewery
Deposit Name
   Saccharomyces cerevisiae
Month of deposit
   June
Deposit Year
   1958
Habitat
   Ale production strain



Tower Fermentation Vessel

[kramerog]

I would say to all of you who are posting theories about why it will or won't work, TRY IT for yourself and post your results.  That's the way citizen science works.  We need more than just a few data points.  And a big thanks to Mark (and Marshall and all the other experimenters) who make us all think and re-evaluate what we think we know.

Understanding why something works or doesn't work is science too and can allow knowledge to be applied to other ways of making starters.  In particular, the biggest issue for me with this method is that I like having my starter finished before I brew; pitching at high krausen adds another complication to the brew day.  The knowledge I gain here can help me make better starters the way I like to make them.

Having said that I may try this method the next time I do a split batch and post the results here.

[denny]

Understanding why something works or doesn't work is science too and can allow knowledge to be applied to other ways of making starters.  In particular, the biggest issue for me with this method is that I like having my starter finished before I brew; pitching at high krausen adds another complication to the brew day.  The knowledge I gain here can help me make better starters the way I like to make them.

Having said that I may try this method the next time I do a split batch and post the results here.

I completely agree.  And I really doubt this method is the be all, end all, ONLY good method.  It's likely just another very good method...but I won't know without trying it and seeing for myself.