[S. cerevisiae]

What do you recommend for very high gravity worts of 1.090 and above?   Wouldn't the higher osmotic stress in these worts indicate a larger starter is required?

Each yeast strain is unique, but higher gravity wort generally requires higher pitching rates due to the fact it is more difficult to dissolve O₂ in high gravity wort, high osmotic pressure causes loss of turgor pressure, and lower dissolved O₂ affects yeast cell heath. With a high gravity wort, it is best to use a strain that has been proven to hold its own against the double whammy of high osmotic pressure and high alcohol. 

I always recommend using yeast cropped from a proven good fermentation for high gravity wort.  In fact, I recommend using cropped yeast for standard gravity brewing over propagating a new culture.  Cropped yeast has proven itself in one's brewery, and it has also had time to adjust to one's brewery.  A brewer really does not know what a strain is capable of producing unless he/she repitches it a couple of times.  I used to use a strain from BrewTek called CL-210 Scottish Bitter.   The initial pitch was okay, but it was not until I had repitched the strain a couple of times that I started to appreciate its uniqueness.

[brewinhard]

I have already answered this question in this thread (page 4).

Gotcha.  Missed that even after reading it twice.  Man, I need new glasses.  Thanks!

[smokeymcb]

Hi all, O.P. here...

I thought I'd give an update as to what I did.  I originally was going to do the shaken not stirred starter with a vial of harvested 34/70 but I think it may have been too old because it did nothing in my starter for 3 days.  I put off brewing while waiting for signs.  I gave up on it and made 2l of starter wort, split it between 2 one gallon jugs and dry pitched half a pack of 34//70 in each.  I shook like crazy and went to brewing. By the time the brew was finished and chilled, the starters were raging.  I pitched them (on a friday) and left for the weekend, so unfortunately, I don't know what kind of lag was involved but everything was cruising when I returned on the sunday.   Today was racking day and the sample tastes amazingly clean and crisp, with no off flavours that I could taste.  I've put it to lager for a few weeks.

I know what I've done isn't really what Mark is suggesting but its kind of along the same lines as there are lots who would call one pack of dry lager yeast in 5.5 gallons of 1.062 wort (FG was 1.007), a severe underpitch which is guaranteed to produce nothing of a drinkable nature.  I will definitely be trying something a little closer to Marks original technique on my next brew as well.

Thanks for teaching me something different Mark, I appreciate the shared knowledge...

[RPIScotty]

Dry yeast is saturated with ergosterol and UFA beyond the levels you could ever get in a home brew starter because it is grown in bioreactors designed to do so. A single package generally has enough nutrient reserves to multiply to full cell density in a 5 gallon batch with no aeration whatsoever. Not saying the technique didn't work for you.

It was a repitch. Not a new package.


Sent from my iPhone using Tapatalk

[RPIScotty]

It was a repitch. Not a new package.

Go back and read his post past the 3rd sentence.

Understood. Didn't catch that.


Sent via Tapatalk

[Frankenbrew]

I finally tried the James Bond method. I had about 120 ml of dense slurry of WLP 029 3rd. generation that was a bit older than two months. I usually pitch the slurry directly from the fridge, but it takes up to 36 hours to form a layer of krausen and start blowing off CO2. I made a 1 L starter using this method, and it took off like a rocket in less than 8 hours. Amazing. I'll never go back if this is what I get from this method. Thanks, Mark!

[HydraulicSammich]

Whew!
Nerve racking trying something new.  I finally gave the procedure a try.  1 L, 1 two month old smack pack.  Pack was expanded.  I was expecting at least twelve hours to high krausen.  Sixteen hours later it appeared high krausen had taken place hours ago.  It probably occurred around the seven hour mark.  Is this possible?  There was a nice slurry at the bottom of the flask like it had dropped out and was going dormant.  Does the age or viability have this kind of effect on high krausen time?  I did use an Erlenmeyer if that makes a difference.  The house temp was around 65.

[Frankenbrew]

Whew!
Nerve racking trying something new.  I finally gave the procedure a try.  1 L, 1 two month old smack pack.  Pack was expanded.  I was expecting at least twelve hours to high krausen.  Sixteen hours later it appeared high krausen had taken place hours ago.  It probably occurred around the seven hour mark.  Is this possible?  There was a nice slurry at the bottom of the flask like it had dropped out and was going dormant.  Does the age or viability have this kind of effect on high krausen time?  I did use an Erlenmeyer if that makes a difference.  The house temp was around 65.

I think the expected peak of krausen occurs sometime around 8 hours.

The other thing I see that you did was to use an Erlenmeyer flask. I think you're supposed to use a one gallon jug so that you can shake the starter wort so hard that it completely turns to foam. You need room enough to create a 4 to 1 ratio of foam to wort.

[klickitat jim]

Im 6 batches into this method, 5 with <1 month old 1056 and 1 with 2 month old 1257. All of these have reached HK at around 8 hrs. I use erlenmeyers but I dont shake, I oxygenate. I dont think that part matters a whole bunch. Though clearly if you are shaking, having a bigger volume of head space will help. Theres optimum and then there's good enough.

[brewday]

I think either way gets the job done.  Though not exactly his method, thanks to Mark the majority of my starters going back to January have been 1L in a flask, hit with the O2 wand and not stirred.  I usually get HK in around 7-8 hours this way.  It's easy to miss.  My results seem to match those reporting on the 1G jug "shake like it owes you" method.

Edit:  Thanks you too, Jim.  I seem to remember you talking about hitting your starters with the wand and stirring slowly around that time.

[HydraulicSammich]

Good info, thanks.
I used a 5 L Erlenmeyer with a solid stopper and was able to shake well.  The short krausen time fooled me.  I totally expected at least 12 hours.  Now I can work it into my timeline.

[klickitat jim]

I think either way gets the job done.  Though not exactly his method, thanks to Mark the majority of my starters going back to January have been 1L in a flask, hit with the O2 wand and not stirred.  I usually get HK in around 7-8 hours this way.  It's easy to miss.  My results seem to match those reporting on the 1G jug "shake like it owes you" method.

Edit:  Thanks you too, Jim.  I seem to remember you talking about hitting your starters with the wand and stirring slowly around that time.

Yes I give 1200ml (because that's about what I can pour off of a 1/2 gallon canned wort before I get to the trub) with o2 for guesstimate 20-30 seconds. I give it a few shakes then add the yeast. I cover with foil and leave it alone. At about 8 hrs its ready.

[S. cerevisiae]

Whew!
Nerve racking trying something new.  I finally gave the procedure a try.  1 L, 1 two month old smack pack.  Pack was expanded.  I was expecting at least twelve hours to high krausen.  Sixteen hours later it appeared high krausen had taken place hours ago.  It probably occurred around the seven hour mark.  Is this possible?  There was a nice slurry at the bottom of the flask like it had dropped out and was going dormant.  Does the age or viability have this kind of effect on high krausen time?  I did use an Erlenmeyer if that makes a difference.  The house temp was around 65.

What was the strain? How big was the Erlenmeyer?  I need data points.

[S. cerevisiae]

Yes I give 1200ml (because that's about what I can pour off of a 1/2 gallon canned wort before I get to the trub) with o2 for guesstimate 20-30 seconds. I give it a few shakes then add the yeast. I cover with foil and leave it alone. At about 8 hrs its ready.

I have always said that my method was a poor man's O₂ bottle and diffusion stone.  Your results matching mine leads me to believe that having the wort saturated early may make a difference in the length of the lag phase. 

I wish that I was closer to retirement.  I would have more time to run experiments that I need to run.  I barely have enough time to brew and maintain my yeast bank.  I finally managed to subculture two strains today that I have put off subculturing since April.  The slants that held the strains were subcultured over a year ago, and one of the cultures is pain in the backside to grow on solid media.   I inoculated 40ml of autoclaved wort with one of the strains even though I do not plan to use it for a couple of weeks because I did not want to have to subculture the strain in a few weeks.  That choice is going to cause me to perform an intermediate step.

[Wort-H.O.G.]

I believe the argument for using a stir plate is that it does continuously oxygenate the wort if a vortex is achieved.

The only time that a stirred starter begins to approach the surface area of a Shaken, not Stirred starter is when a vortex is created.  The vortex is needed overcome the low amount of surface area that is present when a 1L starter is made in a 2L Erlenmeyer flask as well as to overcome the geometry of a Erlenmeyer flask by creating a vacuum.  A stir plate cannot overcome the poor geometry of an Erlenmeyer flask once the culture starts outgassing.

When we use a stir plate to propagate yeast, we are using a process known as stirred suspension cell culturing.  Shear stress is a well-known problem with stirred cultures.  Shear stress is the stress placed on cells in turbulent flow.  The more turbulent the fluid, the greater the amount of shear stress.  I am convinced that the foul odors and tastes that one encounters with a stirred starter are the result of stress, not oxidation, as oxidation should not occur in a culture due the cell density and yeast's affinity for O₂.

Shear stress in stirred cultures is a well studied problem. While we think of growing yeast biomass when the term culturing is thrown around, many other types of cells are propagated using the same basic techniques that we use for yeast (the medium may be different).   A device known as a bioreactor is used for very large scale cell culturing and dry yeast culturing.  There are numerous papers covering this area of research.

Mark's point is that the forces present in a starter that is stirred at such a high speed will cause damage to the yeast cells. It seems it's not so much a biochemical problem but a physical one. Apparently all that slamming around during long periods of stirring is detrimental to the cell walls of the yeast. The shaken not stirred method does employ very vigorous/violent stirring (shaking) but it is for a very short period of time (1 min) such that there is really no physical stress to the yeast. I take his method to heart and really shake the living daylights out of that one gallon jug to the point that the whole 1L starter is completely foam. The maximum degree of air-to-liquid surface area is achieved in that condition.

Yes, the key to success with the method is shaking the medium vigorously enough to turn it completely into foam (or at least darn near it) in a vessel with at least a 4:1 vessel volume to medium volume ratio.  Gas dissolves into a liquid at the interface between the gas and the liquid. The Shaken not, Stirred method works by creating a huge amount of surface area.  A gas-liquid foam has a very high specific surface area.  It is basically pockets of gas encased in thin layers of liquid.  The beauty of the technique is that the O₂ that dissolves while the medium is still foam is available immediately to the culture. 

With the above said, shaking can be eliminated via direct O₂ injection.  However, the technique is no longer low tech and low cost (or as my British friends would say, no longer as cheap and cheerful).

just for reference, my stirred starters dont smell or taste bad nor laden with anything foul...not sure why just is the case.