Author Topic: Yeast propagation at White Labs  (Read 2559 times)

S. cerevisiae

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Yeast propagation at White Labs
« on: June 16, 2015, 05:20:00 PM »
I hope that everyone who took the White Labs tour noticed the big orbital shaker table in the propagation lab.  I did not see a single stir plate in use at White Labs.
« Last Edit: June 16, 2015, 05:26:41 PM by S. cerevisiae »

Offline denny

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Re: Yeast propagation at White Labs
« Reply #1 on: June 16, 2015, 05:38:48 PM »
I hope that everyone who took the White Labs tour noticed the big orbital shaker table in the propagation lab.  I did not see a single stir plate in use at White Labs.

I'll stop using mine as soon as I get a big orbital shaker table!  In the meanwhile, I've proven to myself that a stir plate works better and faster than any other method I've tried.
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Offline brewinhard

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Re: Yeast propagation at White Labs
« Reply #2 on: June 16, 2015, 05:44:30 PM »
I hope that everyone who took the White Labs tour noticed the big orbital shaker table in the propagation lab.  I did not see a single stir plate in use at White Labs.

Was there any oxygen being pumped into this at all? 

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Re: Yeast propagation at White Labs
« Reply #3 on: June 16, 2015, 05:52:29 PM »
Not that I saw, but I only was able to get a glimpse of the room.  The flasks appeared to be standard Erlenmeyer flasks instead of Fernbach flasks.   A Fernbach flask looks like a squat Erlenmeyer flask. Fernback flasks are made for shaking.

Offline rjharper

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Re: Yeast propagation at White Labs
« Reply #4 on: June 16, 2015, 06:01:57 PM »
It's a lot easier (and cheaper) to put a dozen flasks on a shaker table, than line up 12 spinning magnets. I did notice they still use foil crimped around the mouth of the flask, just like us!

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Re: Yeast propagation at White Labs
« Reply #5 on: June 16, 2015, 07:03:54 PM »
Actually, a shaker table is the preferred laboratory device for propagating yeast.  What shaking does is aerate the culture in a low stress way.  Spinning the stir bar fast enough to aerate a culture on a stir plate can place significant shear stress on the cells, resulting in an unhealthy culture. That's why many stirred cultures smell foul.
« Last Edit: June 16, 2015, 07:15:37 PM by S. cerevisiae »

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Re: Yeast propagation at White Labs
« Reply #6 on: June 16, 2015, 07:05:50 PM »
By the way, a shaker table the size that is used at White Labs is significantly more expensive than a comparable number of stir plates.

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Re: Yeast propagation at White Labs
« Reply #7 on: June 16, 2015, 07:31:50 PM »
Actually, a shaker table is the preferred laboratory device for propagating yeast.  What shaking does is aerate the culture in a low stress way.  Spinning the stir bar fast enough to aerate a culture on a stir plate can place significant shear stress on the cells, resulting in an unhealthy culture. That's why many stirred cultures smell foul.

Very interesting. I'm certainly not going to go against your yeast advice Mark. And I only push the stir bar fast enough to get things moving and roused, not to force a maelstrom in the flask!

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Re: Yeast propagation at White Labs
« Reply #8 on: June 16, 2015, 08:29:23 PM »
In my humble opinion, stir plates have been sold to home brewers based on claims that do not hold up under close inspection.  Stirring briskly enough to aerate a culture can result in unhealthy cells due to shear stress.  Stirring slowly does not add much in the way of value because most brewing strains are either non-flocculent or exhibit NewFlo flocculation (FLO is the name for the set of genes that control flocculation).  NewFlo strains remain in suspension until glucose, mannose, maltose, sucrose, and maltotriose reach a genetically set level, and non-flocculent strains seem to want to remain in suspension forever; hence, cells that exhibit either type of flocculation will remain in suspension long enough to achieve maximum cell density without stirring.

Now, there are those who claim that stirring results in higher cells counts.  However, I have never seen viability stain results accompany these claims.  A solution is capable of supporting a maximum number of viable cells.  This number is known as the maximum cell density. Yeast cultures are self-moderating in that all new biomass growth is for replacement purposes only after maximum cell density has been reached. 

The goal of making a starter should be to reach maximum cell density while preserving cellular health, which is why I promote pitching a well-aerated starter at high krausen.  High krausen occurs when maximum cell density has been reached. One should experience high krausen with a 1 to 2 liter starter roughly 12 to 18 hours after inoculation.  Older cultures will take longer to reach high krausen than newer cultures.  Allowing a starter to ferment beyond high krausen results in unnecessary ergosterol and unsaturated fatty acid depletion.  Allowing a starter to ferment to completion places the cells in the yeast equivalent of hibernation.

« Last Edit: June 17, 2015, 03:41:40 PM by S. cerevisiae »

Offline jeffjm

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Re: Yeast propagation at White Labs
« Reply #9 on: June 17, 2015, 01:59:27 PM »
I completely get the idea of having the cells be active.  On the other hand,  I don't want to dilute my batch with several liters of starter wort. How can you minimize the amount of starter wort pitched while keeping the cells active?
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Re: Yeast propagation at White Labs
« Reply #10 on: June 17, 2015, 02:58:16 PM »
In my humble opinion, stir plates have been sold to home brewers based on claims that do not hold up under close inspection.  Stirring briskly enough to aerate a culture can result in unhealthy cells due to shear stress.  Stirring slowly does not add much in the way of value because most brewing strains are either non-flocculent or exhibit NewFlo flocculation (FLO is the name for the set of genes that control flocculation).  NewFlo strains remain in suspension until glucose, mannose, maltose, sucrose, and maltotriose reach a genetically set level, and non-flocculent strains seem to want to remain in suspension forever; hence, cells that exhibit either type of flocculation need help remaining in suspension long enough to achieve maximum cell density.

Now, there are those who claim that stirring results in higher cells counts.  However, I have never seen viability stain results accompany these claims.  A solution is capable of supporting a maximum number of viable cells.  This number is known as the maximum cell density. Yeast cultures are self-moderating in that all new biomass growth is for replacement purposes only after maximum cell density has been reached. 

The goal of making a starter should be to reach maximum cell density while preserving cellular health, which is why I promote pitching a well-aerated starter at high krausen.  High krausen occurs when maximum cell density has been reached. One should experience high krausen with a 1 to 2 liter starter roughly 12 to 18 hours after inoculation.  Older cultures will take longer to reach high krausen than newer cultures.  Allowing a starter to ferment beyond high krausen results in unnecessary ergosterol and unsaturated fatty acid depletion.  Allowing a starter to ferment to completion places the cells in the yeast equivalent of hibernation.

Mark, I hope you know that I have great respect for your knowledge and experience.  But what am I to do when my direct experience contradicts that knowledge?  I don't have the equipment to count cells or assess viability.  I have to base my techniques solely on performance and results.  For many years, I simply shook my starters as you advise.  It worked fine.  But once I was given a stir plate, I found that I could grow more yeast in a shorter time than shaking.  In addition, I got (subjectively) better results using the yeast grown on a stir plate.  So, how do I reconcile my results with your advice?
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Re: Yeast propagation at White Labs
« Reply #11 on: June 17, 2015, 03:23:52 PM »
I completely get the idea of having the cells be active.  On the other hand,  I don't want to dilute my batch with several liters of starter wort. How can you minimize the amount of starter wort pitched while keeping the cells active?

+1.  That is my major concern as well.  How does one handle this issue?

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Re: Yeast propagation at White Labs
« Reply #12 on: June 17, 2015, 03:33:37 PM »
As I have mentioned many times on this forum, yeast cultures are kind of like nuclear weapons in that one only needs to be within a reasonable distance from one's target in order to accomplish the task.   The difference in propagation time between a 1L starter and a 2L start is one replication period (approximately 90 minutes); hence, very little is gained by pitching 2L starter.  Nothing is gained by pitching a 2L starter that has reached quiescence over pitching a 1L starter at high krausen. 

In my humble opinion, modern home brewing yeast pitching dogma is doing more harm than good.  My discussions with the brewers at White Labs only confirmed this belief.  I have pitched as little as 3 billion cells per liter of wort and as much as 20 billion cells per liter of wort.  Both pitching rates created good beer.  The difference between the two extremes is that the 3 billion cells per liter rate allowed the yeast to express its unique character whereas the 20 billion cell pitching rate produced a more generic flavored beer.  Granted, one has to pitch more cells per liter with high gravity beers, but that's only because high osmotic pressure coupled high ethanol levels take their toll on yeast cells, and it is more difficult to dissolve O2 in high gravity wort than it is in lower gravity wort.

Those who have tried my starter method have reported improved fermentation characteristics. A large part of that improvement is pitching at high krausen.  A starter made with extra light DME (e.g., Briess Pilsen) that is shaken until the media is mostly foam at the beginning of fermentation, and not stirred will be very neutral in flavor.  A 5% increase in final boil gravity will allow for a dilution rate of 1L per 5 gallons.  I guarantee that pitching at high krausen instead of waiting until quiescence has been reached will cut your starter volume in half because the cells have not depleted their ergosterol and unsaturated fatty acid reserves, nor have they undergone the survival-related morphological changes that occur at the end of fermentation.  A 1L starter that is pitched at high krausen will usually double cell count-wise by the time that a 2L starter that is pitched after quiescence had been reached exits the lag phase.  The net O2 load from the 1L starter will also be lower because one half of the cells at this point came into the game with non-depleted ergosterol and UFA reserves.  This difference results in a healthier fermentation.

If that information is not enough to convince you, the difference between pitching 200 billion cells and 400 billion cells is insignificant when pitching normal gravity wort.  The maximum cell density for 1L of wort is approximately 200 billion cells.  This limit is controlled by cell size.  The maximum cell density for a 5-gallon batch is 19 * 200 billion = 3.8 trillion cells; hence, neither pitching rate will saturate a 5-gallon batch of wort without significant growth.  As the cell count grows at a rate of 2n, where n equals elapsed clock time divided by the number of minutes in a replication period (around 90 minutes under ideal conditions), the minimum number of doubling periods that are required for each starter size to saturate the wort are as follows:

four_hundred_billion_cell_starter_replication_periods = log(3,800 / 400) / log(2) =  log(9.5) / log(2) = ~4 (arithmetic ceiling taken)

two_hundred_billion_cell_starter_replication_periods = log(3,800 / 200) / log(2) =  log(19) / log(2) = ~5 (arithmetic ceiling taken)

« Last Edit: June 17, 2015, 03:35:08 PM by S. cerevisiae »

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Re: Yeast propagation at White Labs
« Reply #13 on: June 17, 2015, 04:00:24 PM »
I have pitched as little as 3 billion cells per liter of wort and as much as 20 billion cells per liter of wort.  Both pitching rates created good beer.  The difference between the two extremes is that the 3 billion cells per liter rate allowed the yeast to express its unique character whereas the 20 billion cell pitching rate produced a more generic flavored beer.

four_hundred_billion_cell_starter_replication_periods = log(3,800 / 400) / log(2) =  log(9.5) / log(2) = ~4 (arithmetic ceiling taken)

two_hundred_billion_cell_starter_replication_periods = log(3,800 / 200) / log(2) =  log(19) / log(2) = ~5 (arithmetic ceiling taken)

At what point does the number of replication periods begin to have an effect on beer flavor?  I suppose it probably depends on strain and other factors, but are there any studies on this that you are aware of?
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Re: Yeast propagation at White Labs
« Reply #14 on: June 17, 2015, 07:16:44 PM »
At what point does the number of replication periods begin to have an effect on beer flavor?  I suppose it probably depends on strain and other factors, but are there any studies on this that you are aware of?

That is a good question for which I do not have a definitive answer.