Author Topic: Right RPM for stir plate?  (Read 16919 times)

Offline mabrungard

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Re: Right RPM for stir plate?
« Reply #90 on: January 16, 2015, 08:42:14 PM »
Wow! What a great thread that is hidden under this crappy title. I had not considered looking at it until now and am glad I did.

First to the OP's question, I agree that the proper stir plate rpm is that which keeps the yeast in suspension. There is no need or advantage to high rpm and a frothy vortex.

Mark, you have incredible knowledge shared here. I agree that a stir plate is not ideal, but I don't think that its terrible. One thing that is true, is that a stir plate alone is not sufficient to keep a starter aerobic when using typical narrow-ended vessels. There is little chance that there will be enough exchange with the normal atmosphere to transfer enough oxygen. That is why I flood the headspace of my starter flask with ambient air that is filtered through a 0.45 micron filter. That way, I know there IS enough oxygen present in the headspace to transfer into the gently-stirred wort below. Mark, is your problem with stir plates the fact that they aren't keeping the wort aerobic...or some other reason?

According to (Verstrepen KJ, et al.Yeast flocculation: What Brewers Should Know.” Applied Microbiology and Biotechnology, Vol 61, pp 197-205, 2003.), flocculation is generally inhibited during active fermentation by the presence of mannose, maltose, glucose, and sucrose in the wort. So that means that if the yeast tend to quickly settle when you stop stirring, the wort is exhausted. With the information in this thread from Mark, I now know that I should get that starter into the fridge to settle for decanting. I have probably been continuing the stirring for too long. I'll revise my procedures.

Mark, I read your contention that temperature control is not that important. But I'm concerned that your example yeast species may not be a true case in point. While it apparently works for that relatively clean fermenting yeast, I'm curious if that result can be applied across the entire yeast spectrum? I anticipate that it can't. Can you expand on that?
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Offline klickitat jim

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Re: Right RPM for stir plate?
« Reply #91 on: January 16, 2015, 10:31:07 PM »
I remember him delineating between ? positive and ? negative strains, and whatever negative would be fine but the ones that crank out (phenols maybe) probably ought to be temp controlled. But here's the thing. I have temp control, im going to use it, regardless of what the people with letters after their names say. I know for fact that I make my beere better with my temp control. Your mileage may or may not vary

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Re: Right RPM for stir plate?
« Reply #92 on: January 16, 2015, 11:10:39 PM »
My whole issue is that both whitelabs and wyeast promote the use of stir plates. If they were voodoo, I think wyeast and whitelabs would call it out allowing them to sell more yeast.

It's not that stir plates are voodoo science.  It's that the way that stir plates are promoted in home brewing is voodoo science much in the same way that the process of rinsing yeast with and storing it under boiled tap water is voodoo science.   When used with an Erlenmeyer flask and a stir bar, a stir plate does one thing well; namely, keep cells in suspension.  Most of the popular brewing cultures remain in suspension without the aid of a stir plate during propagation.  If these strains did not remain in suspension during propagation, they would have been discarded years ago because production breweries cannot afford to use strains or mixed cultures that are prone to premature flocculation.

Offline Stevie

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Re: Right RPM for stir plate?
« Reply #93 on: January 16, 2015, 11:38:36 PM »
So why would two reputable yeast labs promote them? Obviously, you have done stacks of research, but they are considered industry experts with a few phd's in their stables.

Offline Wort-H.O.G.

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Re: Right RPM for stir plate?
« Reply #94 on: January 16, 2015, 11:48:09 PM »
My whole issue is that both whitelabs and wyeast promote the use of stir plates. If they were voodoo, I think wyeast and whitelabs would call it out allowing them to sell more yeast.

It's not that stir plates are voodoo science.  It's that the way that stir plates are promoted in home brewing is voodoo science much in the same way that the process of rinsing yeast with and storing it under boiled tap water is voodoo science.   When used with an Erlenmeyer flask and a stir bar, a stir plate does one thing well; namely, keep cells in suspension.  Most of the popular brewing cultures remain in suspension without the aid of a stir plate during propagation.  If these strains did not remain in suspension during propagation, they would have been discarded years ago because production breweries cannot afford to use strains or mixed cultures that are prone to premature flocculation.

question Mark: are you saying yeast cell counts/growth for non stir plate starter is the same as stir plate starter-regardless of how long you leave it on stir plate?
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Re: Right RPM for stir plate?
« Reply #95 on: January 17, 2015, 12:54:30 AM »
Mark, is your problem with stir plates the fact that they aren't keeping the wort aerobic...or some other reason?

My problem with stir plates is that they, like yeast rinsing, have been sold to the home brewing community based on faulty information.  A stir plate is a poor investment when used with an Erlenmeyer flask and a stir bar.  This setup has been sold to home brewers as a self-aerating, "set it and forget it" way to propagate yeast.  The craziest thing is that brewers who arrived on the scene after the introduction of stir plates have been taught that starter media is always too foul to pitch.  Foul smelling media is a sign that the yeast cells in one's starter are stressed.

The most critical thing that a new brewer needs to learn when making a starter is that sanitation is even more critical when propagating yeast than it is when making beer.   He/she also needs to learn that the purpose of a starter is to increase yeast biomass, not produce ethanol; hence, nothing is gained by letting a starter run past the exponential phase.  Most importantly of all, aeration is critical to restoring the health of yeast cells that have been in the stationary phase for a long period of time, and that O2 has to be in solution when or shortly after the culture has been pitched.

Quote
Mark, I read your contention that temperature control is not that important. But I'm concerned that your example yeast species may not be a true case in point. While it apparently works for that relatively clean fermenting yeast, I'm curious if that result can be applied across the entire yeast spectrum? I anticipate that it can't. Can you expand on that?

My post was meant to bring attention to the fact that temperature-controlled fermentation chambers are one of the first things that are pushed onto new brewers when they inquire about process improvement, not that there is never a need for temperature control.  More often than not, quality control problems have little to do with whether or not not a brewer is using tight or stepped temperature regulation during fermentation, especially when using a yeast strain that is as forgiving as BRY 96, which is the most popular yeast strain in home and craft brewing by a sizable margin.  The number one thing that will hold brewers back from producing quality beer is less than optimal sanitation. 

Prospective new brewers that discover that I brew often ask me if they can learn how to make quality beer expecting that I will ask them if they know how to cook.  Most are completely floored when I tell them that making quality beer has more to do with how well one can clean than how well one can cook.  Wort tastes nothing like beer because brewers do not make beer, yeast cells make beer; hence, our actions as brewers should be directed at keeping invaders out of the process and treating the yeast culture that we pitch as the most important ingredient.  How we accomplish that feat is through good brewery hygiene, careful post-chilling wort handling, and ensuring that our cultures are biologically clean and healthy.  A temperature-controlled fermentation chamber helps a brewer improve none of the areas listed above.  However, what it will do is mask poor yeast management as well as poor post-chilling wort handling and sanitation practices by suppressing less cold tolerant microflora, which are more often than not are the resident microflora found in one's home.   

Offline hophead636

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Re: Right RPM for stir plate?
« Reply #96 on: January 17, 2015, 01:07:37 AM »

Mark, is your problem with stir plates the fact that they aren't keeping the wort aerobic...or some other reason?

My problem with stir plates is that they, like yeast rinsing, have been sold to the home brewing community based on faulty information.  A stir plate is a poor investment when used with an Erlenmeyer flask and a stir bar.  This setup has been sold to home brewers as a self-aerating, "set it and forget it" way to propagate yeast.  The craziest thing is that brewers who arrived on the scene after the introduction of stir plates have been taught that starter media is always too foul to pitch.  Foul smelling media is a sign that the yeast cells in one's starter are stressed.

The most critical thing that a new brewer needs to learn when making a starter is that sanitation is even more critical when propagating yeast than it is when making beer.   He/she also needs to learn that the purpose of a starter is to increase yeast biomass, not produce ethanol; hence, nothing is gained by letting a starter run past the exponential phase.  Most importantly of all, aeration is critical to restoring the health of yeast cells that have been in the stationary phase for a long period of time, and that O2 has to be in solution when or shortly after the culture has been pitched.

Quote
Mark, I read your contention that temperature control is not that important. But I'm concerned that your example yeast species may not be a true case in point. While it apparently works for that relatively clean fermenting yeast, I'm curious if that result can be applied across the entire yeast spectrum? I anticipate that it can't. Can you expand on that?

My post was meant to bring attention to the fact that temperature-controlled fermentation chambers are one of the first things that are pushed onto new brewers when they inquire about process improvement, not that there is never a need for temperature control.  More often than not, quality control problems have little to do with whether or not not a brewer is using tight or stepped temperature regulation during fermentation, especially when using a yeast strain that is as forgiving as BRY 96, which is the most popular yeast strain in home and craft brewing by a sizable margin.  The number one thing that will hold brewers back from producing quality beer is less than optimal sanitation. 

Prospective new brewers that discover that I brew often ask me if they can learn how to make quality beer expecting that I will ask them if they know how to cook.  Most are completely floored when I tell them that making quality beer has more to do with how well one can clean than how well one can cook.  Wort tastes nothing like beer because brewers do not make beer, yeast cells make beer; hence, our actions as brewers should be directed at keeping invaders out of the process and treating the yeast culture that we pitch as the most important ingredient.  How we accomplish that feat is through good brewery hygiene, careful post-chilling wort handling, and ensuring that our cultures are biologically clean and healthy.  A temperature-controlled fermentation chamber helps a brewer improve none of the areas listed above.  However, what it will do is mask poor yeast management as well as poor post-chilling wort handling and sanitation practices by suppressing less cold tolerant microflora, which are more often than not are the resident microflora found in one's home.

Fully agree cleanliness in the brewhouse + sanitation should be your number 1 goal all the time

Offline klickitat jim

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Re: Right RPM for stir plate?
« Reply #97 on: January 17, 2015, 01:24:11 AM »
I can say that if you listen to some pod casts, glance at some yeast calculators or yeast sales sites, it seems that stirl plates just double yeast growth all on their own. That might be the voodoo he's talking about. I'm finding that growth needs O2 and stir plates won't get O2 in there as I was led to believe. I think a shook non stired starter is better than nothing, a shook non stired starter is better than a non shook stired starter. I now, and for now, think my oxygenated stired starter is about as good as I will get. Stir plate does not add oxygen, it keeps cells moving thats it.

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Re: Right RPM for stir plate?
« Reply #98 on: January 17, 2015, 01:29:55 AM »
question Mark: are you saying yeast cell counts/growth for non stir plate starter is the same as stir plate starter-regardless of how long you leave it on stir plate?
[/quote]

What I am saying is that any difference in viable cell count will be insignificant, and the yeast cells in a starter that is stirred fast enough to dissolve oxygen before CO2 production begins will be significantly more stressed than the cells from a starter that is shaken into foam in a vessel that is at least three times the volume of the starter shortly before or after inoculation and left to do its thing. 

As Jim has already discovered by using O2 and a slow stir rate, the medium from a non-stressed culture does not smell or taste foul.  The only reason to decant is to avoid diluting one's wort.  The improved performance that Jim experienced was due to injecting O2 at the start and pitching at high krausen.


Offline jlevensailor

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Re: Right RPM for stir plate?
« Reply #99 on: January 17, 2015, 01:49:46 AM »
So after 2 days on stirplate my WLP001 and a weak DME 1.1L wort, I put my flask in the fridge, a day later I see white yeast on the bottom!

Question is, while the yeast looks to be more than what I put in there it isn't more than maybe double it. Should I have a larger amount?


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Re: Right RPM for stir plate?
« Reply #100 on: January 17, 2015, 02:55:05 AM »
So after 2 days on stirplate my WLP001 and a weak DME 1.1L wort, I put my flask in the fridge, a day later I see white yeast on the bottom!

Question is, while the yeast looks to be more than what I put in there it isn't more than maybe double it. Should I have a larger amount?


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One can look to double the volume of yeast cells in a 1.1L starter.   That number of cells will get the job done for most normal gravity ales.   I pitch much less than that amount of yeast when brewing British-style beers (often 1/3rd if I know the strain well).

Offline jlevensailor

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Re: Right RPM for stir plate?
« Reply #101 on: January 17, 2015, 02:58:49 AM »
I prefer doing about 7-9ABV DIPAs.  I used beersmith to come up with 1.1L, just wondering if the bottom should have more yeast covered on it..


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Offline Wort-H.O.G.

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Right RPM for stir plate?
« Reply #102 on: January 17, 2015, 03:04:24 AM »
question Mark: are you saying yeast cell counts/growth for non stir plate starter is the same as stir plate starter-regardless of how long you leave it on stir plate?


my stir plate has very low speed...doesn't even make  a dimple on low speed-just swirls the wort. thats how I run my starters. there's just a lot of studies out there that will contradict your premise that a stationary starter without any o2 infusion (what most homebrewers do) will  produce the same amount of viable cells as the same on a stir plate. not my studies, just saying.

edit: and FWIW, I admire your passion for yeast...in all seriousness. It's just your practices are not practical for most homebrewers. Most of us can't count cells, we don't have O2 infusion for starters. We are left to either stationary or occasional shaken starters, or stir plates. For many of us, stir plates produce good and excellent results when it comes to the finished product.
« Last Edit: January 17, 2015, 03:15:15 AM by wort-h.o.g. »
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Offline jjflash

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Re: Right RPM for stir plate?
« Reply #103 on: January 17, 2015, 03:37:16 AM »
So the recommendation is for me to stop using the Erlenmeyer flask / stir bar / stir plate combination.

If I use the Erlenmeyer flask by itself, would it be better to run an air stone continuous, or dose with oxygen?  With a starter with OG 1.035 how much oxygen to add? The standard 1ppm/degree Plato?  Single dose?  Multiple doses?  Let it run 12-18 hours and refrigerate.

I brew big beers only - 1.080 to 1.110+.  I have started to step my starters from 1.035 1 liter first step, refrigerate and decant with yeast to a 1.070 1 liter second step.  I am now testing a new method suggested by Steven Deeds in Brewing Engineering where I use 1 gallon of the final wort for the third step of propagation. Then pitching this yeast into 10-12 gallon batch.   

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« Last Edit: January 17, 2015, 03:49:58 AM by jjflash »
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Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #104 on: January 17, 2015, 05:57:11 AM »
Wow! What a great thread that is hidden under this crappy title.
Yeah, I started this thread just expecting a simple nuts-and-bolts answer.  Then boom...no KA-BOOM!
This Forum is amazing!  A whole bunch of thoughtful, literate, respectful, fun-loving, BEER-loving folks talking about how to brew beer.  What you folks have done here deserves a very long slow clap!
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