[S. cerevisiae]

Yeast calculators are about as useful as toilet paper when it comes to propagating yeast cells.  Yeast cells are living organisms that behave differently in different environments.  The only way to know how a yeast culture is going to behave in one's brewery is to use it and take very good notes.

As I have said many times, the difference between a 1L starter and a 2L starter is approximately 90 minutes of propagation time, making the argument for a 2L starter when pitching normal gravity beer a non-sequitur.  Now, the difference between a 1L starter and a 5L starter is log(5) / log(2)  * 90 = 208 minutes, or 3.5 hours of propagation time.  However, one is looking a step rate of 22 / 5 = 4.4 when pitching the cells from a 5L starter into a 22L batch of wort.  It takes approximately log(4.4) / log(2) = 2.14 replication periods to reach maximum cell density when pitching at that rate.   In practice, we should step between 10 and 20 for most batches, especially if we plan to repitch the slurry.  Pitching at a higher rate than that tends to lead to declining culture health, as the average cell age increases with each pitch.

The key to successful fermentation is to pitch enough healthy cells at the peak of their performance into well-aerated wort to get the job done.  The osmotic pressure difference between the cell contents and 1.056 wort is not high enough to cause dehydration and loss of turgor pressure, resulting in cell shrinkage and wrinkling of the cell plasma membrane as happens when one pitches a starter into 1.080 wort.  Additionally, the solubility of O₂ decreases as wort gravity increases (Henry's Law).  In essence, we have to pitch a higher number of cells when pitching high gravity wort because of cell loss coupled with lower growth rates and cell health due to lower gas (O₂) solubility.

[klickitat jim]

Yeast calculators are about as useful as toilet paper when it comes to propagating yeast cells.  Yeast cells are living organisms that behave differently in different environments.  The only way to know how a yeast culture is going to behave in one's brewery is to use it and take very good notes.

As I have said many times, the difference between a 1L starter and a 2L starter is approximately 90 minutes of propagation time, making the argument for a 2L starter when pitching normal gravity beer a non-sequitur.  Now, the difference between a 1L starter and a 5L starter is log(5) / log(2)  * 90 = 208 minutes, or 3.5 hours of propagation time.  However, one is looking a step rate of 22 / 5 = 4.4 when pitching the cells from a 5L starter into a 22L batch of wort.  It takes approximately log(4.4) / log(2) = 2.14 replication periods to reach maximum cell density when pitching at that rate.   In practice, we should step between 10 and 20 for most batches, especially if we plan to repitch the slurry.  Pitching at a higher rate than that tends to lead to declining culture health, as the average cell age increases with each pitch.

The key to successful fermentation is to pitch enough healthy cells at the peak of their performance into well-aerated wort to get the job done.  The osmotic pressure difference between the cell contents and 1.056 wort is not high enough to cause dehydration and loss of turgor pressure, resulting in cell shrinkage and wrinkling of the cell plasma membrane as happens when one pitches a starter into 1.080 wort.  Additionally, the solubility of O₂ decreases as wort gravity increases (Henry's Law).  In essence, we have to pitch a higher number of cells when pitching high gravity wort because of cell loss coupled with lower growth rates and cell health due to lower gas (O₂) solubility.

You lose me easily and frequently but that high gravity explanation is awesome. I did not know that. I knew it took more yeast, now I understand why.

[Pi]

Allow me to clarify:
Using Mr Malty,for 5.5 gallons of a 1.052 lager and 1 vial of WLP830 manufactured 8/28/15, Jamil's calculator recommends building 4.97 Liters of 1.030 starter.  400 billion cell count.
To be clear i am not planning on dumping the full 5 liters into my wort! The Starter fermented out in about 24hrs and is resting comfortably at 45* settling out. Sunday afternoon I'll decant and pitch the cake along with about.3l spent wort.
Now I'm no expert but I've been brewing lagers for roughly 9 years. And when i wing it and underpitch (ie. a 1 liter starter) Yeast gets stressed, my lagers come out sweet and under-attenuated. Conversely, When i use relatively fresh yeast, build a starter following Mr Malty's guidelines aerate, pitch low and come up to fermentation temp, I get very clean lagers.  I cant argue the explaination below. after reading it several times, walking away, then reading several more times it does make sense. I also know what works for me and what dont. Guess I'm just stupid

[S. cerevisiae]

A big part of your problem is that you are letting the starter ferment out.  One should never let a starter ferment out.  That's a no-no when propagating yeast.   A starter is not a small batch of beer.  It is a propagation medium, and should be treated as such. 

If you pitch at high krausen, you can can cut your cell count in half because the cells are still in the exponential phase with non-depleted ergosterol and unsaturated fatty acid (UFA) reserves.  Allowing a starter to ferment beyond high krausen results in unnecessary ergosterol and unsaturated fatty acid (UFA) depletion because all reproduction beyond that point is for replacement only and mother cells share their ergosterol and UFA reserves with all of their daughters.  It also results in the yeast cells undergoing survival-related morphological changes that have to be reversed before the cells can start to take in nutrients and expel waste products through their cell walls.  Quiescent cells place a higher initial O₂ load on the wort.


Do you happen to be using a stir plate?    If so, that is part of your problem.  Stir plates subject yeast cells to shear stress.

[Pi]

I do not understand a lot of the technical specifics, but after much thought I must agree. It makes sense that after you grow a bunch of yeast, then they go back to sleep, then wake them back up...
So, in the future, I will try growing 1l of 1.030, and pitch the whole liter at high krausen/no stir plate. What temp. do you recommend for a lager starter?

[klickitat jim]

I do not understand a lot of the technical specifics, but after much thought I must agree. It makes sense that after you grow a bunch of yeast, then they go back to sleep, then wake them back up...
So, in the future, I will try growing 1l of 1.030, and pitch the whole liter at high krausen/no stir plate. What temp. do you recommend for a lager starter?

I want to know what Mark says about lager starter temp. But if he didn't say, my thinking is that i would do my lager starter at lager temp, because i wouldnt be decanting. It is probably going to take a little longer to reach high krausen at 50 vs room temp. I also worry about having enough, so I would either pitch two 1L starters or two smack packs into 2L shaken not stired, for my 6 gallon batches.

[Pi]

[/quote]
 I also worry about having enough, so I would either pitch two 1L starters or two smack packs into 2L shaken not stired, for my 6 gallon batches.
[/quote]
 Think I could split one WL vial between 2 1l?

[smokeymcb]

I do not understand a lot of the technical specifics, but after much thought I must agree. It makes sense that after you grow a bunch of yeast, then they go back to sleep, then wake them back up...
So, in the future, I will try growing 1l of 1.030, and pitch the whole liter at high krausen/no stir plate. What temp. do you recommend for a lager starter?

I want to know what Mark says about lager starter temp. But if he didn't say, my thinking is that i would do my lager starter at lager temp, because i wouldnt be decanting. It is probably going to take a little longer to reach high krausen at 50 vs room temp. I also worry about having enough, so I would either pitch two 1L starters or two smack packs into 2L shaken not stired, for my 6 gallon batches.

Sixty degrees  Fahrenheit is way too cold for a starter.  That's why your starters are taking forever to reach high krausen.   Starters should be incubated at 25C/77F (i.e., room temperature), regardless of yeast species (ale and lager yeast strains are different yeast species).  The goal of a starter is to increase yeast biomass, not make beer.

[69franx]

I also worry about having enough, so I would either pitch two 1L starters or two smack packs into 2L shaken not stired, for my 6 gallon batches.
[/quote]
 Think I could split one WL vial between 2 1l?
[/quote]

This is what I have been doing and having good results with it. Not to say its correct or proper form, but its working for me

[Werks21]

A big part of your problem is that you are letting the starter ferment out.  One should never let a starter ferment out.  That's a no-no when propagating yeast.   A starter is not a small batch of beer.  It is a propagation medium, and should be treated as such. 

If you pitch at high krausen, you can can cut your cell count in half because the cells are still in the exponential phase with non-depleted ergosterol and unsaturated fatty acid (UFA) reserves.  Allowing a starter to ferment beyond high krausen results in unnecessary ergosterol and unsaturated fatty acid (UFA) depletion because all reproduction beyond that point is for replacement only and mother cells share their ergosterol and UFA reserves with all of their daughters.  It also results in the yeast cells undergoing survival-related morphological changes that have to be reversed before the cells can start to take in nutrients and expel waste products through their cell walls.  Quiescent cells place a higher initial O₂ load on the wort.


Do you happen to be using a stir plate?    If so, that is part of your problem.  Stir plates subject yeast cells to shear stress.

What is the best/easiest/most reliable way to determine high krasuen in a small starter? starters are hard to read. (for me anyway)

[a10t2]

Got a vial of WLP830 and i am making a 5l starter for a Vienna brewing this sunday. I want to make another 5l starter for a similar batch i'm doing a couple days later, but was wondering what the best way to grow. Should i decant the first starter and dump another 5l of wort on that cake then split that between the 2 batches, or pinch a little cake from the first starter and start anew?

In my experience, stirred 8°P starters grow 100-150 billion cells per liter of medium. So you should be somewhere in the vicinity of double your target cell density, and I would think you could safely split the slurry in half to pitch both batches.

On the other hand, if pitching substantially more than that is giving you the results you want, by all means keep doing that. In that case my vote would be for "pinching".

[S. cerevisiae]

What is the best/easiest/most reliable way to determine high krasuen in a small starter? starters are hard to read. (for me anyway)

Usually, but not always, lack of a krausen is a sign that a starter was underaerated or there was too little or far too much carbon (extract).  However, in those cases, the end of the exponential phase should look like low krausen on a normal fermentation.  There will be very thin layer of foam, often only in patches, covering the surface of the starter.  High krausen on a normal healthy 1L or larger starter should produce a krausen that is at least 1/4" thick (I have had krausens on starters that were over 1" thick).  Experience is the best teacher with strains that do not produce much of a head.  One should always try to be in a situation where one can periodically monitor the progress of a starter (or a have a camera that can record what is happening during incubation).  As always, anything that happened during incubation that did get not recorded digitally or on paper did not occur.  A brewing log is a brewer's best friend.

[brewinhard]

Mark,

Regarding lager starters I know you mentioned that they should be completed around 75F to increase cell biomass.  If one wanted to pitch that starter at high krausen into a cooled 50F wort couldn't the yeast experience some sort of shock due to the more than 20F temperature difference?  If so, what do you recommend in this situation?

[S. cerevisiae]

The reason I made that comment is because incubation at low temperatures slows metabolism, and anything that slows metabolism slows replication.  I made the comment when I noticed that people were placing their starters in fermentation chambers.

With that said, I do not see a problem with lowering the culture temperature to pitching temperature before pitching it into a batch of wort.  Placing a culture in a refrigerator set to 50F is not going to drop the temperature of the culture in a second or two, which is what happens when we pitch a culture at 75F into 50F wort.   Let's put things in human terms.  If we walk into a refrigerator set to 50F, we will not experience an internal temperature drop as fast as if we were thrown into a large body of 50F water.

[Werks21]

Usually, but not always, lack of a krausen is a sign that a starter was underaerated or there was too little or far too much carbon (extract).  However, in those cases, the end of the exponential phase should look like low krausen on a normal fermentation.  There will be very thin layer of foam, often only in patches, covering the surface of the starter.  High krausen on a normal healthy 1L or larger starter should produce a krausen that is at least 1/4" thick (I have had krausens on starters that were over 1" thick).  Experience is the best teacher with strains that do not produce much of a head.  One should always try to be in a situation where one can periodically monitor the progress of a starter (or a have a camera that can record what is happening during incubation).  As always, anything that happened during incubation that did get not recorded digitally or on paper did not occur.  A brewing log is a brewer's best friend.

Thanks, And that bit about the brewing log is spot on. I didn't record any real data on my fermentations for a while after I started brewing and now I'm kicking myself. I'm all over it now though.