Author Topic: HELP: WLP540 Abbey IV Attenuation  (Read 7078 times)

Offline ultravista

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #30 on: October 17, 2014, 02:19:08 PM »
If you start chilling you likely won't go any lower.  If you're happy with 1.021 that's fine, but if you think it should be lower I would just wait.

I've left big beers for two months to reach terminal gravity.   Sometimes you just have to be patient.

I haven't left beer on the yeast cake for longer than 6 weeks. It's about 45 degrees now, perhaps too cold for the yeast to continue nibbling.

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #31 on: October 17, 2014, 02:20:47 PM »
That makes sense.

So, have you done a 2 step starter with a higher gravity wort for the second step?  I might try that next time I want to go straight to a very high gravity batch(1.090+).  Of course, there's a certain point where it's just as easy to make a lower gravity batch of beer as your "starter".

Yes, I have stepped starters in gravity many times.  I have also performed three step 1.020 -> 1.040 -> 1.060 starters when culturing yeast straight from a bottle of Chimay.  I recently taught a very talented young brewer the process.  He too was a doubting Thomas until he tried it on a RIS.   He said that it went against everything that he had read on Internet forums.

If you think about it, there's nothing magical about the process.  The first level starter does all of the heavy lifting when it comes to resuscitating  the culture and getting the cell count up.  It takes at most two replication periods to reach maximum cell density when the slurry from the 1L starter is pitched into the 3L starter. 

I have found that one does not even need a stir plate for this process.  I used to use 5L and 10L media bottles before I took a hiatus from the hobby (they look like large versions of the orange-capped media bottle shown in one of my other posts).  The beauty of using a media bottle is that it can be capped after pitching and shaken until the media is almost all foam.   I still shake the 40ml starters that I inoculate from slant.  I  sold my 5L and 10L media bottles while on hiatus from the hobby.  I have been thinking about ditching my stir plate for a shaker.  Large media bottles are expensive enough that I can justify purchasing a used shaker and a couple of used shaker flasks (they look like Erlenmeyer flasks with baffles on the bottom).  I am a little like James Bond in that I prefer my cultures shaken, not stirred. :)


Offline narvin

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #32 on: October 17, 2014, 02:30:17 PM »
I also start cultures from a bottle at 1.20 or so, with other starters being 1.035-1.040.  I generally don't have attenuation problems, especially using WLP530, but 540 was one in the past I've noticed this issue with.  It produces attenuation in the mid 70s, as advertised, but not the 88% that Rochefort gets.  If I'm going to do steps, most of the time I'd rather reuse the yeast from a batch of beer and get two beers.

Re: Beersmith,  he's using degrees Plato for the apparent attenuation numbers.  It seems like ProMash does this as well.  Plato and specific gravity are similar, and measure similar things, but they aren't linear and start to differ more at higher gravities.  Degrees plato is extract percentage by weight, and specific gravity is a measure of density.  I'm not really sure which one is more appropriate, though.

Offline Joe Sr.

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #33 on: October 17, 2014, 02:54:39 PM »
I also start cultures from a bottle at 1.20 or so

This is exactly what I was thinking.  If I'm culturing from a bottle, I start low and step the gravity up with each successive step.  Same methodology as S. is talking about, and it works quite well.
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Offline narcout

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #34 on: October 17, 2014, 04:48:06 PM »
He said that it went against everything that he had read on Internet forums.

That surprises me.  It's not that foreign of a concept.  Isn't it also covered in Yeast?

I have been thinking about ditching my stir plate for a shaker.

Is there a particular advantage to one over the other? 
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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #35 on: October 17, 2014, 06:07:36 PM »
Is there a particular advantage to one over the other?

Most amateur brewers are under the false belief that a stir plate spun at slow to medium speed increases yeast cell count, which could not be further from the truth.  A culture that is shaken until the media is almost all foam immediately after pitching has more initial dissolved oxygen than a starter that is merely pitched and placed on a stir plate at a low to medium speed.  A stirred culture has to be stirred at a fast enough speed to create a vortex down to the stir bar in order to provide adequate aeration.  CO2 is denser than air, so there is very little in the way gas exchange in a flask after significant CO2 production has started.   

I am also not convinced that spinning a stir bar at a high rate of speed does not beat the cells up because every starter that I have made on a stir plate has had the telltale smells and tastes associated with yeast stress.  I have never had a shaken starter that I could not pitch without decanting the supernatant.
 
The major advantage that a stir plate offers over merely shaking a culture until it is almost all foam immediately after pitching is that it keeps flocculent yeast strains from prematurely flocculating. However, that advantage is almost insignificant when creating a starter because the goal is to produce yeast cells, not fully attenuate the wort; hence, we should be stepping or pitching the culture after we have reached maximum cell density.

Now, a stir plate combined with continuous aeration is an entirely different topic.  However, that process requires us to sterilize (at least sanitize) another piece of gear.



Offline narcout

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #36 on: October 17, 2014, 06:34:34 PM »
A stirred culture has to be stirred at a fast enough speed to create a vortex down to the stir bar in order to provide adequate aeration.  CO2 is denser than air, so there is very little in the way gas exchange in a flask after significant CO2 production has started.

Oh man, there was a long thread about this topic on the NB forum a couple of years ago that delved into partial pressures of gases, etc.  It got a bit heated as I recall.

The major advantage that a stir plate offers over merely shaking a culture until it is almost all foam immediately after pitching is that it keeps flocculent yeast strains from prematurely flocculating.

What about driving off CO2, is that worth anything?

Now, a stir plate combined with continuous aeration is an entirely different topic.

What about hitting a stir plate starter with a bit of oxygen prior to pitching?

Actually, I remember that Kaiser did some experiments on this topic. 

http://braukaiser.com/blog/blog/2013/03/19/access-to-air-and-its-effect-on-yeast-growth-in-starters/
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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #37 on: October 18, 2014, 05:09:49 PM »
Actually, I remember that Kaiser did some experiments on this topic. 

http://braukaiser.com/blog/blog/2013/03/19/access-to-air-and-its-effect-on-yeast-growth-in-starters/

That experiment pretty much correlates with my hypothesis. 

This part of Kai's hypothesis is on the money. 

"yeast growth in wort is limited by available oxygen for sterol production.  That means that access to more O2 allows more cells to be grown."

However, the maximum number of viable cells that can be produced is limited by the maximum cell density per milliliter.

With that said, one thing that I am certain most readers will overlook in the experiment is the inoculation rate of 10.8 billion cells per liter.   That inoculation rate is a fraction of the number of viable cells that are available from the average White Labs vial (it's an order of magnitude less than that of a relatively new White Labs vial). 

To grow from 10.8 billion cells per liter to 250 billion cells per liter (which is above the normal maximum cell density of 200 million cells per milliliter), requires the culture to undergo log2(250 / 10.8 ) replication events.

Note: log2 is the logarithm base-2 function, which can be performed on calculators that do not support it by taking the base-10 logarithm of 200 / 10  over the base-10 logarithm of 2 (i.e., log(250/10) / log(2)) or the natural (base-e) logarithm of 200 / 10  over the natural logarithm of 2 (i.e., ln(250/10) / ln(2)).  This formula is the inverse of the basic exponential growth model after n replication events, which is cell_count_after_n_events = initial_cell_count x 2n.

number_cell_replication_events_kai_experiment = log(250/10.8 ) / log(2) = 4.53


To grow from 100 billion cells per liter to 250 billion cells per liter, the culture has to undergo log2(250 / 100) replication events.

number_cell_replication_events_fresh_white_labs_vial = log(250/100) / log(2) = 1.32

Stir plates appear to be yet another situation where the amateur brewing community has taken a technique that is rooted in science and generalized it to a point where the outcome from the technique no longer holds. In my humble opinion, little to nothing is gained by using a stir plate, stir bar, and a 2L to 5L Erlenmeyer flask at typical amateur brewer starter volumes. A stirred culture without continuous aeration offers no advantage over a well-shaken culture when propagating a White Labs vial, and a well-shaken culture has fewer possible sources of contamination. 

A cheap and easy solution for shaken 1L starters is a 1-gallon glass jug with a sanitizable cap (be careful when pouring hot liquid in a glass jug because most jugs are made from untempered soda lime glass).  For those who are not price sensitive, a 4L to 6L screw cap Erlenmeyer flask such as Corning model 4995-4L or 4995-6L can be a good investment if one takes care of one's gear, especially if purchased used.  A  4L to 6L screw cap Erlenmeyer affords one the advantage of being able to boil one's culturing media in the flask.   Larger starters will require a larger jug or flask (shoot for at least three times the starter volume).

Remember, the key to the well-shaken starter technique is using a vessel that is at least three times the size of the starter volume and shaking the starter until it is almost all foam after pitching.  Periodically shaking the starter during the first six to twelve hours can be beneficial.

« Last Edit: October 18, 2014, 06:21:10 PM by S. cerevisiae »

Offline narcout

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #38 on: October 18, 2014, 06:01:12 PM »
A stirred culture without continuous aeration offers no advantage over a well-shaken culture when propagating a White Labs vial, and a well-shaken culture has fewer possible sources of contamination.

Doesn't Kai's experiment show that the stir plate helps to aerate the culture?  I guess that is what I took away from the fact that the starter covered with an airlock grew less yeast than the starter covered with foil which grew less yeast than the uncovered starter. 

If no aeration was being provided by the stir plate, wouldn't you expect to see the same growth regardless of how tightly the flask was covered?  Maybe a repeat experiment with control cultures not on stir plates would be needed to really answer that.

Periodically shaking the starter during the first six to twelve hours can be beneficial.

If nothing else, I suppose a stir plate can do the shaking for you while you are sleeping or at work.


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Offline denny

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #39 on: October 18, 2014, 06:53:46 PM »
I know of a stir plate aeration study being done now by a homebrewer and a couple microbiologists.  It's appearing that there is virtually no O2 added from the stirring motion, but the results aren't complete yet.
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Offline narcout

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #40 on: October 18, 2014, 07:37:21 PM »
Cool.  I hope someone will post the results when available.  I suppose it doesn't really matter all that much, as long as you are pitching the desired amount of healthy cells.

In the meantime, I've got a Saison to brew (sans starter altogether in fact).
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Offline erockrph

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #41 on: October 19, 2014, 04:34:54 AM »
This is starting to make me feel better about never bothering to invest in a stir plate. I may have to try the "shake to a froth" technique in one of my 3-gallon Better Bottles the next time I make a starter.
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Offline denny

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #42 on: October 19, 2014, 03:42:55 PM »
This is starting to make me feel better about never bothering to invest in a stir plate. I may have to try the "shake to a froth" technique in one of my 3-gallon Better Bottles the next time I make a starter.

I made shaken starters for years and felt like I got great performance. Then someone gave me a stir plate.  My starters are not only done sooner, but my subjective analysis is that the yeast performs better.  YMMV.
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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #43 on: October 19, 2014, 09:56:32 PM »
I made shaken starters for years and felt like I got great performance. Then someone gave me a stir plate.  My starters are not only done sooner, but my subjective analysis is that the yeast performs better.  YMMV.

There's no doubt that a stir plate results in reduced fermentation times.  A stir plate keeps most if not all of the viable cells in suspension (that's what it is designed to do).  However, getting a starter to ferment to completion sooner is not the goal of making a starter.  The goal of a starter is to increase viable yeast biomass, and no appreciable viable biomass is created after the end of the deceleration phase (which is technically the tail end of the log or exponential phase).   

With that said, my results have been the opposite of yours.  I have experienced no appreciable performance improvement since switching to using a stir plate.  What I have experienced are stressed yeast cultures (e.g., ale yeast strains throwing sulfur), which is why I started to question the value-add of a stir plate as used by most amateur brewers.  I am hoping to be able to find the time to test well-shaken at pitching time, continuously stirred, and continuously shaken starters over the winter.


Offline Stevie

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Re: HELP: WLP540 Abbey IV Attenuation
« Reply #44 on: October 19, 2014, 10:27:28 PM »

...which is why I started to question the value-add of a stir plate as used by most amateur brewers.
Good thing I'm a homebrewer not an amateur brewer.