Stirred Fermentation

Big brew on New Year's Day, my pals and I brewed up 25 gallons of a Stone IPA clone. It was the perfect opportunity for me to put my new carboy stirplate to use, to see how this will affect the ferment and the final product as well. I woke up this morning to a very happy brew closet, the beer on the stirplate had twice as much krausen and twice the airlock activity of the other beers, It was impressive enough that I took some video for anyone who's interested.

Stirred Fermenter

interesting! it'll be neat to see how the stirred batch compares to the others. i wonder if it'll make a difference in the final product or just ferment out faster than the others and taste the same..

Awesome!

What's that taped to the conical?

HawkATP said:

What's that taped to the conical?

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temperature probe.

carboy stirplate with no blow-off tube?

livin' dangerous.

Sulli, glad you are doing this. I have wanted to try this for years now and have only done experiments with my boil keggle to see if a little stir bar could make a vortex... which it did! I pressure ferment in a Sanke, and have been wanting to try this in that situation with a cut diptube. Please let us know, as soon as you know, how this works out on an actual fermentation. I will be checking this thread with every post in anticipation. Thanks for doing the work for us, lol.

I was not so much interested with fermentation, as I am with aging/lagering being sped up through the increased surface area contact that it should provide during those stages (depending on whether you are doing a lager or ale that is). Regardless of your results, I will still hold out hope for the accelerated lagering this could bring to the table... but, still anxious to see you succeed on the fermentation part of the experiment. You The Man!

motobrewer said:

carboy stirplate with no blow-off tube?

livin' dangerous.

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I think the vortex should keep everything out of the airlock, but I can't wait to hear if it does or not!

I just went down and checked on it, the krausen is now up to the mouth of the carboy, so I quickly put a blow off tube on. Livin' dangerous indeed!

WortMonger said:

Sulli, glad you are doing this. I have wanted to try this for years now and have only done experiments with my boil keggle to see if a little stir bar could make a vortex... which it did! I pressure ferment in a Sanke, and have been wanting to try this in that situation with a cut diptube. Please let us know, as soon as you know, how this works out on an actual fermentation. I will be checking this thread with every post in anticipation. Thanks for doing the work for us, lol.

I was not so much interested with fermentation, as I am with aging/lagering being sped up through the increased surface area contact that it should provide during those stages (depending on whether you are doing a lager or ale that is). Regardless of your results, I will still hold out hope for the accelerated lagering this could bring to the table... but, still anxious to see you succeed on the fermentation part of the experiment. You The Man!

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My original intent with building this stir plate was to speed up the fermentation and aging process for my meads. This beer isn't really big enough to justify the use of a stir plate but it seemed like a good opportunity to do some side by side comparisons.

Wow, live updates, lol. That means it wouldn't keep it out of my spunding valve assembly, as is, so I am very tankful for the heads up on me being wrong in my assumption. What is it they say about people who assume... oh yeah, ass out of u and me, lol. Great work, very interested. I wish there were a way to measure gravity drops in real time for this experiment for an even more scientific approach.

Sulli said:

My original intent with building this stir plate was to speed up the fermentation and aging process for my meads. This beer isn't really big enough to justify the use of a stir plate but it seemed like a good opportunity to do some side by side comparisons.

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Good to understand your starting point with this. I think this will even help temperature differentials equalize faster since you are breaking up the stratification that can happen from the walls to the center of the vessel. I'm interested in how fast it could take a fermentation from say 62*F for the first 3 days to 68*F for the remainder of primary. Then when it is time to crash cool... I bet it will drop like a rock after you are at temp and have stopped everything moving around.

WortMonger said:

Good to understand your starting point with this. I think this will even help temperature differentials equalize faster since you are breaking up the stratification that can happen from the walls to the center of the vessel. I'm interested in how fast it could take a fermentation from say 62*F for the first 3 days to 68*F for the remainder of primary. Then when it is time to crash cool... I bet it will drop like a rock after you are at temp and have stopped everything moving around.

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Interesting...I'll keep an eye on the temp after I turn the stir plate off and let you know.

Im testing a stirplate for another guy on the boards and the only thing that i do different is i use an airlock but i run it empty. Only sanitized with a piece of sanitized foil on it so the carboy can "breathe" I dont really see the point of a stirred fermentation if your not getting any more oxygen to the yeast (which i always assumed was the point). Just my 2cents.

Rock Chalk

Chris

Dirty said:

Im testing a stirplate for another guy on the boards and the only thing that i do different is i use an airlock but i run it empty. Only sanitized with a piece of sanitized foil on it so the carboy can "breathe" I dont really see the point of a stirred fermentation if your not getting any more oxygen to the yeast (which i always assumed was the point). Just my 2cents.

Rock Chalk

Chris

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It is important that you provide enough oxygen to the yeast at the beginning of fermentation. The problem with oxygen exposure during fermentation, is that it activates metabolic pathways that produce off-flavors. Beer fermentations that have been exposed to oxygen have higher concentrations of acetaldehyde, due to oxidation of ethanol into acetaldehyde.
The main reason to put a carboy on a stirplate is to keep the yeast in suspension and hopefully, get a cleaner, more fully attenuated beer. [this remains to be seen.]
The reason you let starters breath, is because you are not fermenting them for the taste, you are fermenting them to maximize growth and health in the yeast. This is also why it is good practice to decant your starters before pitching the yeast, as they tend to taste like crap.

Sulli said:

It is important that you provide enough oxygen to the yeast at the beginning of fermentation. The problem with oxygen exposure during fermentation, is that it activates metabolic pathways that produce off-flavors. Beer fermentations that have been exposed to oxygen have higher concentrations of acetaldehyde, due to oxidation of ethanol into acetaldehyde.
The main reason to put a carboy on a stirplate is to keep the yeast in suspension and hopefully, get a cleaner, more fully attenuated beer. [this remains to be seen.]
The reason you let starters breath, is because you are not fermenting them for the taste, you are fermenting them to maximize growth and health in the yeast. This is also why it is good practice do decant your starters before pitching the yeast, as they tend to taste like crap.

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^ +1 What Sulli said is completely accurate for a fermentation vs. a starter for yeast growth.

Thanks for doing this, I am mainly commenting because it will be easier to track this post and I am very interested in how this turns. I just got my first stir plate for Christmas and have always wondered about yeast agitation during fermentation. I thought I read in Yeast by JZ that there was some side effect to this but it seemed pretty esoteric, and I would love to hear how this works out from a practical standpoint. Thanks again.

Cheers

subscribed.

though without a carboy stir-plate OR pre-fermentation oxygen, I regularly see apparent attenuation around 86% with many strains of yeast (particularly safale us-05 and various belgian strains) which begs the question...

why?

mightynintendo said:

subscribed.

though without a carboy stir-plate OR pre-fermentation oxygen, I regularly see apparent attenuation around 86% with many strains of yeast (particularly safale us-05 and various belgian strains) which begs the question...

why?

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There is potential for expedited fermentation of lagers and ales here. I'd assume the OP is prompted by a desire to make beers which ferment/clean-up/flocc faster than those without stirring.

I am under the impression that stirring it will cause increased ester production. I wish I could provide the reference but I cannot remember which book I read it in.

WortMonger said:

Wow, live updates, lol. That means it wouldn't keep it out of my spunding valve assembly, as is, so I am very tankful for the heads up on me being wrong in my assumption. What is it they say about people who assume... oh yeah, ass out of u and me, lol. Great work, very interested. I wish there were a way to measure gravity drops in real time for this experiment for an even more scientific approach.

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You could measure drops in gravity if you have a scale that would be able to measure in grams. Place the scale under the stir-plate and monitor the drop in weight due to conversion of sugars to alcohol.

Granted it would be a small change, but when you look at an ale with a SG of 1.040 dropping to 1.012 times the total volume that would be a significant number of grams.

You could also suspend the whole apparatus on a pivot balance and monitor the change in horizontal axis of the pivot arm. Put the carboy+stir plate on one end of an arm and the equal weight of water in a bucket on the other end of the arm (equal distances from the center pivot point). Either measure the amount of change in degrees or remove the necessary amount of water to make the pivot arm horizontal again. Then weight the amount of removed water.

So I took some gravity readings this morning before work. The results are not quite what I had expected. Keep in mind, I pitched my yeast about 3 days ago.
The OG on this beer was 1.063, it was supposed to be 1.069, but that's another story.
Here are the gravity results:
Stirred carboy - 1.015
Non-stirred carboy - 1.026
Conical - 1.014
The gravity from the conical surprised me. It's basically done, but then again I did pitch a very large healthy starter, and because of the larger mass of liquid in the conical it was generating more heat than the non-stirred carboys. But still, I didn't expect it to have such a low specific gravity.
The temperature of the stirred carboy has stayed about 4 degrees higher than the non-stirred carboys the entire time, and basically mimicked that of the conical, and as you could see from the video it had a very active fermentation.
The real surprise, though, came when I tasted the stirred carboy sample and the conical sample side by side, they are almost like two different beers.
The stirred sample is a light honey color, it has just a hint of fruitiness and caramel up front and then a smooth bitterness to the finish, seemed well balanced, tasted very much like a Stone IPA.
The conical sample is more of a light amber color, same sweetness up front, but the bitterness is rougher and more pronounced, could have been the C02 that is still in solution, but it didn't seem nearly as smooth.
Since the size and shape of the conical is entirely different from the carboy, maybe I should expect a slightly different beer.
I look forward to tasting all of them together after they are kegged, carbed and aged a few weeks.
So far it seems the stir-plate did not have a negative affect on the flavor, and quite possibly improved it, I will know for sure in a few more weeks.
BTW the yeast cake on the bottom of the stirred carboy is MASSIVE, almost an inch and a half of pure ivory colored yeast.

Hey I started a Sierra Nevada pale clone. I pitched at right above sixty with OG of 1.062 I am suppose to dry hop at a week or when fermentation is near completion. First what is The best way to dry hop with pellets, second I have not had any airlock action how do I know when I should add hops.

davedave4420 said:

Hey I started a Sierra Nevada pale clone. I pitched at right above sixty with OG of 1.062 I am suppose to dry hop at a week or when fermentation is near completion. First what is The best way to dry hop with pellets, second I have not had any airlock action how do I know when I should add hops.

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Leave it alone for 2 weeks and then take a gravity reading, your final gravity should probably be around 1.012 give or take a few points. Once the gravity is stabilized, i.e. not dropping anymore, put the hops in a hop sack tie a knot in the top and stick it in your fermenter. Some people like to transfer the beer to a secondary fermenter before dry hopping but, personally, I don't think it's necessary. Your call.
edit: whoops, forgot to mention...sanitize the hop bag by boiling it for a few minutes, or rinsing it with star-san, before adding the hops. cheers.

So everything about each batch is equal except the containers and/or stir bar? Assuming the yeast was pitched and mixed well prior to transferring to each respective vessel is correct, no? You said that there was more liquid in the conical than the other vessels, right? I am anxious to see how they all taste when the slower beers finish...

mightynintendo said:

So everything about each batch is equal except the containers and/or stir bar? Assuming the yeast was pitched and mixed well prior to transferring to each respective vessel is correct, no? You said that there was more liquid in the conical than the other vessels, right? I am anxious to see how they all taste when the slower beers finish...

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The conical got the same amount of yeast relative to the volumes.
I pitched 200 milliliters of slurry per 5 gallons, so the conical got 400 mils. The yeast slurry was mixed well and it all came from the same flask.
Doh! just re-read your post and realized you were asking about the volume of liquid in the conical not the amount of "liquid yeast" in the conical. Yes...the conical has more beer, 10 gallons of it.

Sulli said:

Leave it alone for 2 weeks and then take a gravity reading, your final gravity should probably be around 1.012 give or take a few points. Once the gravity is stabilized, i.e. not dropping anymore, put the hops in a hop sack tie a knot in the top and stick it in your fermenter. Some people like to transfer the beer to a secondary fermenter before dry hopping but, personally, I don't think it's necessary. Your call. edit: whoops, forgot to mention...sanitize the hop bag by boiling it for a few minutes, or rinsing it with star-san, before adding the hops. cheers.

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Thank you very much and how long do I leave the hop bag in?

davedave4420 said:

Thank you very much and how long do I leave the hop bag in?

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Usually a week will suffice.

Sulli, I suspect the increased temperature in the stirred variant is from friction, which in my way of brewing is not a worry since increased temperature can happen in a pressurized fermentation with no ill effects. I am pumped about your results so far. I honestly was only interested in stirring from a maturation/aging faster standpoint, so your data is good to know. I can also assume (there is that damned word again that gets me into trouble) that a lot of the flavor aspects are from more suspended yeast and from CO2 being less in solution from being beaten out... but again that is only a assumption. I can't wait till the final finished product tasting information from you on these batches.

TimT said:

I am under the impression that stirring it will cause increased ester production. I wish I could provide the reference but I cannot remember which book I read it in.

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Again, I am thinking this is due to people thinking about open air starter type stirred fermentations. This is a closed air, as in "NO O2 after oxygenation and pitching" type of fermentation, and IMHO all that is happening is yeast are allowed a greater chance to eat more and faster. Even though the un-stirred is a point less, I feel they will equal out in time due to the stirred version being "green" a shorter amount of time.

I cannot wait to try this with a pressurized fermentation to see just how much one could shave off the time of a beer. My beer is already fully carbonated after primary all on it's own. Imagine carbed, matured, and in my glass in just over two weeks, and I mean READY not just DRINKABLE!:rockin:

If the beers reached different temperatures during the first 36 hours, they will likely taste different. Temperature variances as little as 2 degrees F can have a dramatic influence on the flavor of any beer, especially ales fermenting above 60. Precisely controlled fermentation temperature is one of the most crucial elements in brewing. If your beers taste different, I believe this will come mainly from the different temperatures at which they spent their first 36 hours and have less to do with CO2 and/or yeast in suspension. I am interested to know how the final flavors of all three examples compare.

WortMonger said:

Sulli, I suspect the increased temperature in the stirred variant is from friction, which in my way of brewing is not a worry since increased temperature can happen in a pressurized fermentation with no ill effects. I am pumped about your results so far. I honestly was only interested in stirring from a maturation/aging faster standpoint, so your data is good to know. I can also assume (there is that damned word again that gets me into trouble) that a lot of the flavor aspects are from more suspended yeast and from CO2 being less in solution from being beaten out... but again that is only a assumption. I can't wait till the final finished product tasting information from you on these batches.
Again, I am thinking this is due to people thinking about open air starter type stirred fermentations. This is a closed air, as in "NO O2 after oxygenation and pitching" type of fermentation, and IMHO all that is happening is yeast are allowed a greater chance to eat more and faster. Even though the un-stirred is a point less, I feel they will equal out in time due to the stirred version being "green" a shorter amount of time.

I cannot wait to try this with a pressurized fermentation to see just how much one could shave off the time of a beer. My beer is already fully carbonated after primary all on it's own. Imagine carbed, matured, and in my glass in just over two weeks, and I mean READY not just DRINKABLE!:rockin:

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heh heh, I applaud your enthusiasm Sounds like you enjoy playing with your beer as much as I do. I've been reading up on your method of using pressurized sanke kegs, sounds very interesting. I've put my buddies 20 gal boil kettle on this stir plate, dropped a stir bar in, and had a vortex going through about 10 gallons of water.[In fact I'm considering using this method in combination with an immersion chiller to cool my next 10 gal batch of wort] So I'm sure you could make it work with a sanke keg. Your gonna need some strong-ass magnets though.

mightynintendo said:

If the beers reached different temperatures during the first 36 hours, they will likely taste different. Temperature variances as little as 2 degrees F can have a dramatic influence on the flavor of any beer, especially ales fermenting above 60. Precisely controlled fermentation temperature is one of the most crucial elements in brewing. If your beers taste different, I believe this will come mainly from the different temperatures at which they spent their first 36 hours and have less to do with CO2 and/or yeast in suspension. I am interested to know how the final flavors of all three examples compare.

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The stirred carboy kept about the same temp as the conical. I've got my Ranco set at 68/1/66/1 and it does a pretty good job holding 'em steady, I only have one temperature probe though, so I tape it the outside of the conical, since I figure it's going to be generating the most heat. This makes is hard to get the carboys much higher than about 65 degrees because the A/C is trying to keep the temps down on the conical. Maybe this is going to skew the results on the side by side between the carboys since the two non-stirred carboys fermented about 4 degrees lower than the stirred carboy; now that both the conical and the stirred carboy have slowed up, the temps have equalized across all the fermentation vessels and the non-stirred carboys have gained a few degrees. Could all equal out in the end. What are your thoughts?

Sulli said:

heh heh, I applaud your enthusiasm Sounds like you enjoy playing with your beer as much as I do. I've been reading up on your method of using pressurized sanke kegs, sounds very interesting. I've put my buddies 20 gal boil kettle on this stir plate, dropped a stir bar in, and had a vortex going through about 10 gallons of water.[In fact I'm considering using this method in combination with an immersion chiller to cool my next 10 gal batch of wort] So I'm sure you could make it work with a sanke keg. Your gonna need some strong-ass magnets though.

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You Sir are a bastard, for making me have to check this thread every time I walk into the room, lol. Enthusiastic is an understatement! Great work Sulli. So, these magnets you speak of, lol, strong due to the yeast or strong due to the amount of liquid. I am wondering about the tiny stir bar cutting through all the yeast you are seeing in your stirred carboy being the problem you are alluding to, but I am unclear. A little clarity on this matter will surely keep me up thinking even more tonight, lol.

WortMonger said:

You Sir are a bastard, for making me have to check this thread every time I walk into the room, lol. Enthusiastic is an understatement! Great work Sulli. So, these magnets you speak of, lol, strong due to the yeast or strong due to the amount of liquid. I am wondering about the tiny stir bar cutting through all the yeast you are seeing in your stirred carboy being the problem you are alluding to, but I am unclear. A little clarity on this matter will surely keep me up thinking even more tonight, lol.

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lol much?

How else does one show he is laughing at what he said so another doesn't get the wrong impression when I call him a bastard for completely blowing my mind by doing an experiment I wish I could do right this second? I wouldn't want him to take me serious on saying something I meant in jest.

i'm just teasing you because you lol'd three times in one post like a grandmother on facebook.

You're a grandmother on facebook... what is a facebook?

^ humor

< Idiot

< drunk