So stir plates are great for yeast starters and most references report almost 1/3 to double the yeast count when used right? So why not have your primary on a stir plate? Wouldn't your yeast ferment faster and more efficient? Everybody says don't splash your fermenter around because you can oxidize it, but the things filled with CO2.... what would be the harm if it was on a stir plate? Just something I have been thinking about for a few days...
if stir plates for starters why not primary?
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TipsyDragon
Well-Known Member
5 gallons of wort is heavy? might crush the stir plate.
OldManHouston
Well-Known Member
The stir plate agitates out the CO2 and draws in oxygen. Would probably be a pretty quick way to wind up with 5 gallons of heavily oxidized beer.
Dunerunner
Well-Known Member
Starters are for yeast production, or reproduction and it is aerobic activity. You don't really want that in your beer, you want yeast making alcohol, an anaerobic activity.
That was my thought (but I don't know those words).
As I have understood, while your starter is on a stirplate, you are not really fermenting anything. It is not until the oxygen is spent that the yeast can start to work on the sugars. It is pretty evident because once I started using a stirplate for my starter, I no longer created a krausen. Assuming that is true, a stir plate is practically all growth, and no fermentation.
You see how that would be a problem in the primary....
Joe
ThePearsonFam
Well-Known Member
+1 starters are to grow yeast, not make beer...
OldManHouston said:
If there is no oxygen in the fermenter how are you going to oxidize it? If anything the oxygen is in the solution right? The yeast are going to use that... so you guys are saying that moving the yeast constantly so they don't settle makes them act differently then if you don't move them? Im pretty ignorant about most of this so it more an interested query that anything... and I would think your yeast starters don't taste good because there 75 percent yeast, im sure that's not tasty...
Dunerunner
Well-Known Member
You could always ferment in a magnetic field!!
http://www.brewsnews.com.au/2011/04/magnetised-fermentation-to-revolutionise-brewing/
http://www.ufpe.br/biofisica/bp034263j.pdf
http://www.brewsnews.com.au/2011/04/magnetised-fermentation-to-revolutionise-brewing/
http://www.ufpe.br/biofisica/bp034263j.pdf
I assumed that you would not use an airlock. Without an airlock the vortex brings oxygen to the yeast. That is the point of a stir plate, not just keeping the yeast in motion.
During a typical fermentation it looks like there is plenty of motion that occurs with fermentation.
That magnetic field thing is pretty awesome! Imagine drinking your beer two weeks after making it!!
Maybe im a little numb but I still don't understand how you pull oxygen into your starter when it gets filled with co2 from the yeast... at some point its gone right? Airlock means air out not in... after the first hours once the yeast start going all that air that was in it is purged I would think...? No am I stupid?
Maybe im a little numb but I still don't understand how you pull oxygen into your starter when it gets filled with co2 from the yeast... at some point its gone right? Airlock means air out not in... after the first hours once the yeast start going all that air that was in it is purged I would think...? No am I stupid?
kpr121
Well-Known Member
I think you are right.
But the whole point of using a stir plate is to bring oxygen into the wort so that the yeast can reproduce. So if there is no oxygen to get into the primary, all you are doing is stirring up the wort. The yeast moves around as much as it needs to pretty well by itself. I guess using a stirplate on your primary could work if you underpitched and wanted to get cell counts up, but usually there is enough O2 in solution for reproduction to occur anyhow.
I think it comes down to "don't fix what ain't broken".
kpr121
Well-Known Member
I want to visit Dr. Butcher, check out the last pic in that article.
kpr121
Well-Known Member
Nope aluminum foil only
...and that is why you don't want an airlock on your starter. Just covering it with sanitized aluminum foil will keep bugs out and still allow for air to exchange. As long as you are providing an exchange of air, you are providing oxygen. As long as your are providing oxygen, you are inhibiting fermentation. If there is no fermentation, there is no CO2. Now, if you do not use a stirplate, then you are experiencing a mini fermentation in your starter; so don't confuse the two methods. The stir plate is a different animal.
I could have this wrong, but I am reasonably confident.
Would someone who is certain mind confirming or correcting?
Joe
chaydaw
Well-Known Member
And even if you did use an airlock on your primary stirplate the liquid would be immediately sucked back down inot your beer. At that point air would be continually be drawn into your primary and cause oxidation.
Not trying to take sides on this one, but I don't see how this would happen. I can see that a stir plate would cause the layer of CO2 to get mixed up and cause O2 to come in to contact with the wort. But, I don't see how it would lower the pressure inside the fermentor to cause a suck back. Am I over looking something here?
ReverseApacheMaster
Well-Known Member
That's my thought.
If you have ever seen fermentation through a better bottle or glass carboy you'll notice it is very cloudy. That is the yeast floating around and sucking up all the sugar to create alcohol. It doesn't need help.
CaptainCoconut
Well-Known Member
Stirplates don't create a vacuum. I hope I'm just misunderstanding what you wrote, because that's a pretty ignorant statement.
To the OP, there's a certain cell count that makes the best tasting beer. Increasing cell count with a stirplate in primary (not that it would even work right without oxygen being free to come in) would have the same effect as overpitching: your beer won't develop the right flavors.
I agree with Captaincoconut.
To start with something basic, two of the results from yeast processing sugar are alcohol and the formation of CO2. If there is no fermentation occuring, there is no CO2. Keep that in mind.
If I understand things right, the small vortex that a stirplate creates is there to facilitate an exchange between the surface area of the wort and the air in the environment. It is accomplishing the same thing as shaking a carboy or spraying wort, but it is doing it to the 10th degree. An air lock is like a liquid check valve, so if you use one, by design, it will not let air into the environment. Without air constantly being introduced to the environment, a stirplate is pretty much useless. So stirplate = foil topped, if no stirplate, air lock or foil would both work (although some argue the pressure created by the airlock once CO2 builds has a negative impact on yeast health, so it may be best to omit them from starters all together). While yeast is on a stirplate (and is constantly being fed oxygen) fermentation is not occuring. It is all growth. If a starter is not placed on a stir plate (and given enough time) fermentation is occuring, and CO2 is being produced.
As the Captain mentioned, the vortex from a correctly used stirplate should not be able to create a vacuum, and will not result in suckback. However.....
....I think the poster who mentioned the vacuum argument may have been confused by an event that can occur during fermentation. If the wort (which I guess at this point is technically beer) is cooled after it has already reached an equilibrium of CO2 in solution, the cooling action will increase its ability to "absorb" CO2, and will start to pull CO2 from the environment. This results in the vacuum that can empty an airlock or suck-back through a blowoff.
Similarly, this is where you hear brewers mention warming up a carboy 2 weeks after fermentation has stopped and "magically restarting fermentation" based on seeing airlock activity. In reality, warming the beer creates the opposite of the vacuum effect, and CO2 is forced out of the solution, and back out the airlock.
So I suppose that if you made a starter a few days ahead of time without a stirplate (and complete fermentation had occured) and used an airlock on your starter, and then put the entire thing into your fridge, the starter wort will cool and could suck the liquid from the airlock......but that is making a lot of assumptions, and that person is not really handling their starters correctly.
Again, feel free to correct anything I said if it was off base.
Joe
To start with something basic, two of the results from yeast processing sugar are alcohol and the formation of CO2. If there is no fermentation occuring, there is no CO2. Keep that in mind.
If I understand things right, the small vortex that a stirplate creates is there to facilitate an exchange between the surface area of the wort and the air in the environment. It is accomplishing the same thing as shaking a carboy or spraying wort, but it is doing it to the 10th degree. An air lock is like a liquid check valve, so if you use one, by design, it will not let air into the environment. Without air constantly being introduced to the environment, a stirplate is pretty much useless. So stirplate = foil topped, if no stirplate, air lock or foil would both work (although some argue the pressure created by the airlock once CO2 builds has a negative impact on yeast health, so it may be best to omit them from starters all together). While yeast is on a stirplate (and is constantly being fed oxygen) fermentation is not occuring. It is all growth. If a starter is not placed on a stir plate (and given enough time) fermentation is occuring, and CO2 is being produced.
As the Captain mentioned, the vortex from a correctly used stirplate should not be able to create a vacuum, and will not result in suckback. However.....
....I think the poster who mentioned the vacuum argument may have been confused by an event that can occur during fermentation. If the wort (which I guess at this point is technically beer) is cooled after it has already reached an equilibrium of CO2 in solution, the cooling action will increase its ability to "absorb" CO2, and will start to pull CO2 from the environment. This results in the vacuum that can empty an airlock or suck-back through a blowoff.
Similarly, this is where you hear brewers mention warming up a carboy 2 weeks after fermentation has stopped and "magically restarting fermentation" based on seeing airlock activity. In reality, warming the beer creates the opposite of the vacuum effect, and CO2 is forced out of the solution, and back out the airlock.
So I suppose that if you made a starter a few days ahead of time without a stirplate (and complete fermentation had occured) and used an airlock on your starter, and then put the entire thing into your fridge, the starter wort will cool and could suck the liquid from the airlock......but that is making a lot of assumptions, and that person is not really handling their starters correctly.
Again, feel free to correct anything I said if it was off base.
Joe
CaptainCoconut
Well-Known Member
The pressure associated with heating and cooling a carboy has to do with the thermal expansion of the air, not so much the CO2 going in and out of solution. If you put an airlock on a completely empty carboy, you'll notice the same pressure changes with heating and cooling. Or throw an empty and capped 2-liter bottle in the freezer for a minute or two.
The magnetic fermentation thing sure looks like an April Fool's joke to me.
CaptainCoconut
Well-Known Member
+1
I also noticed the "magnetized" picture is just a photo negative of the "non-magnetized" picture. "Dr. Butcher" doesn't add credibility, either. And running cars on "magnet beer"?
Great points. I stand corrected. Thanks for posting that.
Well I have learned alot.. so what I have gathered is that with the constant introduction of oxygen the yeast grow more that ferment correct? I didn't know this, I mean they obviously are still eating though right, but they reproduce more when there is more oxygen? If this is true then yeah that would be terrible for your primary...
Think I've read something about it helping to give a bit of aeration to primary within 12 hours of pitching for bigger beers. Not sure if this is true, maybe it'd help if yeast was under pitched, but then maybe you'd just want to pitch more yeast than risk oxidation?
Okay, let's step back here a moment.
1. Using a stirplate starter accomplishes three things:
a. It keeps yeast from accumulating on the bottom, which increases the yeast cell's contact with the sugars
b. the vortex creates a small amount of air movement in the vessel; if there isn't any obstruction to air moving in or out of the starter (i.e, if you use foil and not an airlock), this creates a continuous gas exchange that allows the starter to remain oxygenated.
c. It drives off any CO2 produced, which would prevent oxygenation of the starter to an extent.
2. Oxygen in solution allows yeast to reproduce, as oxygen is necessary for them to create cell membrane material. Also, yeast in an oxygenic solution will metabolize aerobically; it is only when there is no oxygen that they will metabolize anaerobically - i.e., by fermentation. So if you want healthy yeast, you need oxygen. If you want beer, you want no oxygen.
Oxygenating wort before pitching is a sort of compromise between these two things. You give them one shot of oxygen to get numerous and happy, and then they need to start fermenting to survive. Sometimes, with very big beers, two shots of oxygen are helpful, as it is difficult to get enough oxygen in solution in one go. That's what ChillWill was referring to. But that's a special case; usually not necessary, especially if you oxygenate with an oxygen tank.
3. Beer fermenters aren't open to the air. Also, a normal stirplate isn't nearly powerful enough to get the entire fermentation into a vortex - unless you do 1-gallon batches. So any effect it would have would be restricted pretty much the the bottom of the fermenter - stirring up any trub that forms.
Is that a good thing? It may increase the fermentation rate - marginally, at best. It may also create negative effects on the beer by making sure the break material, dormant yeast, and hop particles don't settle out as well.
I don't think there would be a huge difference one way or the other. But I think that if there was a difference, it would be small and negative. Experiment, by all means! But don't hold your breath waiting for me to try this. I don't see the point.
But I salute the OP for thinking outside the box. That's the sort of thinking we need, really. Just that sort of thinking plus a bit more information backing it up.
1. Using a stirplate starter accomplishes three things:
a. It keeps yeast from accumulating on the bottom, which increases the yeast cell's contact with the sugars
b. the vortex creates a small amount of air movement in the vessel; if there isn't any obstruction to air moving in or out of the starter (i.e, if you use foil and not an airlock), this creates a continuous gas exchange that allows the starter to remain oxygenated.
c. It drives off any CO2 produced, which would prevent oxygenation of the starter to an extent.
2. Oxygen in solution allows yeast to reproduce, as oxygen is necessary for them to create cell membrane material. Also, yeast in an oxygenic solution will metabolize aerobically; it is only when there is no oxygen that they will metabolize anaerobically - i.e., by fermentation. So if you want healthy yeast, you need oxygen. If you want beer, you want no oxygen.
Oxygenating wort before pitching is a sort of compromise between these two things. You give them one shot of oxygen to get numerous and happy, and then they need to start fermenting to survive. Sometimes, with very big beers, two shots of oxygen are helpful, as it is difficult to get enough oxygen in solution in one go. That's what ChillWill was referring to. But that's a special case; usually not necessary, especially if you oxygenate with an oxygen tank.
3. Beer fermenters aren't open to the air. Also, a normal stirplate isn't nearly powerful enough to get the entire fermentation into a vortex - unless you do 1-gallon batches. So any effect it would have would be restricted pretty much the the bottom of the fermenter - stirring up any trub that forms.
Is that a good thing? It may increase the fermentation rate - marginally, at best. It may also create negative effects on the beer by making sure the break material, dormant yeast, and hop particles don't settle out as well.
I don't think there would be a huge difference one way or the other. But I think that if there was a difference, it would be small and negative. Experiment, by all means! But don't hold your breath waiting for me to try this. I don't see the point.
But I salute the OP for thinking outside the box. That's the sort of thinking we need, really. Just that sort of thinking plus a bit more information backing it up.
Reviving an old thread here, but this is the most in depth thread I found on the subject.
Great summary Skyforger. I'd like to push the discussion on another aspect : Kraussen.
Lets assume that you are running a stir plate on a primary fermenter with an air lock. At one point, all the O2 will have either been pushed out by CO2 pressure, consumed by the yeast or oxidized the wort. I'm not so much concerned about how much oxidation will occur, but one could start the stir plate after 12 hours when there's enough CO2 in solution to push out all O2 right away.
What interests me is what would happen on the surface of the wort : Can we expect enough turbulence in the wort to diminish CO2 solubility ? If so, then the lower concentration of CO2 in solution would raise the pH. How would that impact fermentation on the final taste and on yeast stress ?
Also, if the surface of the wort slowly rotates due to bottom stiring, maybe this would dampen the Kraussen formation. That would be great if we could use air locks instead of having to clean blow-off tubes !
My stir plate can't hold a carboy, so i'm out. I'd still love to ear about someone testing this in a comparative test. Maybe running the stir plate throughout primary fermentation would indeed be a bad idea since it would prevent all solids to settle down, but it might be fine in the first few days if it can prevent having to clean Kraussen everywhere.
Great summary Skyforger. I'd like to push the discussion on another aspect : Kraussen.
Lets assume that you are running a stir plate on a primary fermenter with an air lock. At one point, all the O2 will have either been pushed out by CO2 pressure, consumed by the yeast or oxidized the wort. I'm not so much concerned about how much oxidation will occur, but one could start the stir plate after 12 hours when there's enough CO2 in solution to push out all O2 right away.
What interests me is what would happen on the surface of the wort : Can we expect enough turbulence in the wort to diminish CO2 solubility ? If so, then the lower concentration of CO2 in solution would raise the pH. How would that impact fermentation on the final taste and on yeast stress ?
Also, if the surface of the wort slowly rotates due to bottom stiring, maybe this would dampen the Kraussen formation. That would be great if we could use air locks instead of having to clean blow-off tubes !
My stir plate can't hold a carboy, so i'm out. I'd still love to ear about someone testing this in a comparative test. Maybe running the stir plate throughout primary fermentation would indeed be a bad idea since it would prevent all solids to settle down, but it might be fine in the first few days if it can prevent having to clean Kraussen everywhere.
That's an idea, although it complicates things a bit :
- I'd need a glass jug since the plastic ones around here are way too thin and I might get oxidation due to the porous material.
-I'd have to bottle condition if I want to taste a carbonated product.
-I'd also need a gallon jug for un-stired wort, otherwise I can't compare krausen tickness.
-I'd have to make sure the lowest setting on the stir plate doesn't make a bigger swirl in the jug then the highest setting in the bucket.
And the end result might not be conclusive anyway because the ratio in Krausen surface area / volume of wort in a bucket is much lower then in a 1 gal jug. If I can set the stir plate low enough, it might still be a good way to compare the impact on taste, if not the impact on krausen.
I guess I must be missing something. Why do you want to use a stir plate if it's not for continuous aeration?
BeerWard
Well-Known Member
I did something similar for my first mead. 2gallon bucket with 1.5 gallons of must. I put it on a stir plate and turned it on several times a day. It was UNDER an airlock. The intent was actually to degas the mead and allow fermentation to continue. Also it would kick any yeast back up in suspension. When I turned on the stir plate the airlock went crazy, as CO2 was rapidly coming out of solution. Then the activity died down, and gravity confirmed fermentation was stopped, I racked off the lees and aged in a carboy. I don't see why this couldn't be done for beer, but eventually, you would want to stop and let everything settle. Also a stirplate to agitate 5 gallons would be pretty large.
https://www.homebrewtalk.com/f30/degas-strir-plate-223259/
https://www.homebrewtalk.com/f30/degas-strir-plate-223259/
I don't see any problem with this and have wanted to try it in my 15 gallons batches in a Sanke keg. I know a small stir bar will stir a keg boil kettle from my experiments. If no O2 is being introduced, all you are doing is allowing more surface area to the yeast.
TIL that degasing is just as important to yeast then nutrient addition in mead. Now I just need to find out if someone does it by continuous low-agitation instead of high-agitation a few times a day.
kaboom505
Active Member
(new guy begging apologies if looking more stupid than usual)
I see mentioned, especially in the bigger beer recipes, "rousing the yeast" periodically during primary fermentation (this is still in the "normal" range of beers so it isn't anything exotic like adding more yeast/wort). If "rousing" is just getting things mixed up - wouldn't a stir bar gently swirling down there keep everything moving and avoid the need to "rouse" altogether?
The enginerd in me likes learning about all of this - the beer drinker (and SWMBO) is happy with volumes of mild and ESB so I've really got nothing in this...
I see mentioned, especially in the bigger beer recipes, "rousing the yeast" periodically during primary fermentation (this is still in the "normal" range of beers so it isn't anything exotic like adding more yeast/wort). If "rousing" is just getting things mixed up - wouldn't a stir bar gently swirling down there keep everything moving and avoid the need to "rouse" altogether?
The enginerd in me likes learning about all of this - the beer drinker (and SWMBO) is happy with volumes of mild and ESB so I've really got nothing in this...
Handsaw
Well-Known Member
Here it is a year and a half since the last post. Has anyone done an experiment to verify that this is a good idea or a bad idea?
I found this thread because I'm thinking of this same thing.
I'm of the opinion that even if you start the stir plate (assuming that it will actually stir that much wort) right from the git go then sucking the air down into the wort will just let the yeast multiply quicker, not necessarily to a bigger population since when the O2 is gone, they start making alcohol. The stirring would just be to keep the yeast in suspension so they can help make alcohol instead of just lying on the bottom and starving.
I found this thread because I'm thinking of this same thing.
I'm of the opinion that even if you start the stir plate (assuming that it will actually stir that much wort) right from the git go then sucking the air down into the wort will just let the yeast multiply quicker, not necessarily to a bigger population since when the O2 is gone, they start making alcohol. The stirring would just be to keep the yeast in suspension so they can help make alcohol instead of just lying on the bottom and starving.
There appears to be a market for doing this at the commercial level:
http://www.alfalaval.com/campaigns/...ication_note_beer_fermentation_March_2010.pdf
I do forced ferments of about 1L on a stir plate to get my potential FG for a batch. Keeping the yeast in suspension certainly accelerates fermentation. I haven't figured out how to try this on a large scale yet.
http://www.alfalaval.com/campaigns/...ication_note_beer_fermentation_March_2010.pdf
I do forced ferments of about 1L on a stir plate to get my potential FG for a batch. Keeping the yeast in suspension certainly accelerates fermentation. I haven't figured out how to try this on a large scale yet.
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