Stirred Fermentation

Williams 728
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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!:mug: 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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These are the magnets I have mounted on my stir plate, next time I build one of these I'll probably go to the next size up. The reason they need to be strong is that there is a lot of resistance from the volume of liquid you are trying to spin, so it tends to decouple the stir bar from the magnets at high speeds, not that you need high speeds to keep the yeast in suspension, it's just cool to be able to pull a vortex through 6 gallons of liquid. :D I'm using a 1.5" standard stir bar, but I have some dumbell shaped stir bars on the way, I think they will work better with the uneven convex surface of a carboy.
 
I had a couple of brewing comrades over last night, and we did some sampling on these beers, and several varieties of micro brews [I have the hangover to prove it. :drunk: oy.]
The stirred carboy is now at 1.014; non-stirred 1.016; conical 1.012. I have to say, tasting these beers at varying specific gravities, has been very educational, especially for my palate. I'm really amazed at how much of a difference just a couple of points in gravity can make to the finish of a beer.

As far as flavor goes, all of the samples are very similar.
The sample from the conical has the best finish so far, I think this is mainly due to it being a slightly drier beer, like I said, I was surprised that I could detect a difference with only 2 points of gravity, but it was definitely there.
The stirred beer tastes great, If it drops those last 2 points of gravity, it will be an exceptional beer. I can't get Stone beers in Salt Lake City:mad:, I'm going to have to make a trip to Evanston so I can do a side by side.
Gonna leave em at temp for another week, then dry hop for one more.
:mug:
 
So Sulli, explain real quick the stirring regiment (like when you started and when you ended the stir/etc). Is it still being stirred to help with maturation, or is it stopped to speed up settling? I am just curious. Oh, and the two points difference could be due to a difference in pitching rate or the shape of the vessel. I know you said you got the right amount for each, but unless all three batches were inoculated and then split, I think you would be off a little. I am so pumped there were no ill effects.
 
When I thought about doing this I thought about treating it like a starter for at least the first 24 hours and put foil over the carboy instead of an air lock. I now have an oxygen setup though so extra oxygen would be trapped in by the airlock until it got used up or diluted and pushed out with the CO2. I could see this as a replacement for the O2 though. I got a free, full medical tank plus won a gift certificate that got me an .5 micron stone so I'm set for a while in that regard. Still, I think looking at turning this into an oxygenation technique for the first 24/36 hours might be worth looking into.
 
WortMonger said:
So Sulli, explain real quick the stirring regiment (like when you started and when you ended the stir/etc). Is it still being stirred to help with maturation, or is it stopped to speed up settling? I am just curious. Oh, and the two points difference could be due to a difference in pitching rate or the shape of the vessel. I know you said you got the right amount for each, but unless all three batches were inoculated and then split, I think you would be off a little. I am so pumped there were no ill effects.
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Let's see...I started the stir plate right when I pitched my yeast, and it ran for about 4 days, I'm using WLP007 so as soon as it flocculated, I could see it cruising around in big globs inside the carboy. That's when I turned the stir plate off, mainly, like you said, to let things settle out. In retrospect I'm thinking maybe I should have just let it run for a full two weeks. I dunno, experimentation is always full of 'should have's' and 'what-if's', next time I'll do it a little different. Probably run the stir plate for a full 2 weeks. So far, though, I'm pleased with the results. Thanks for askin' :)
 
Hermit said:
When I thought about doing this I thought about treating it like a starter for at least the first 24 hours and put foil over the carboy instead of an air lock. I now have an oxygen setup though so extra oxygen would be trapped in by the airlock until it got used up or diluted and pushed out with the CO2. I could see this as a replacement for the O2 though. I got a free, full medical tank plus won a gift certificate that got me an .5 micron stone so I'm set for a while in that regard. Still, I think looking at turning this into an oxygenation technique for the first 24/36 hours might be worth looking into.
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^Worth thinking about.
 
Sulli said:
[...]could have been the C02 that is still in solution, but it didn't seem nearly as smooth..
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Is it possible that the dissolved CO2 is skewing your gravity readings, or are you degassing your samples? The conical would have the most dissolved CO2, which might explain the lower gravity reading. I have no idea how you're measuring gravity, but just an idea if it's not something you've thought about. :)

Cheers!
 
GNBrews said:
Is it possible that the dissolved CO2 is skewing your gravity readings, or are you degassing your samples? The conical would have the most dissolved CO2, which might explain the lower gravity reading. I have no idea how you're measuring gravity, but just an idea if it's not something you've thought about. :)

Cheers!
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I do gravity readings with a refractometer, so this shouldn't be an issue.
 
Sulli said:
I do gravity readings with a refractometer, so this shouldn't be an issue.
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Surprisingly, it is. I also use a refractometer, and have found that the corrected gravity readings are as much as 5 points off unless I degass the sample.
 
GNBrews said:
Surprisingly, it is. I also use a refractometer, and have found that the corrected gravity readings are as much as 5 points off unless I degass the sample.
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Really? I had no idea...so, how would you degass a drop of liquid?
 
Sulli said:
Really? I had no idea...so, how would you degass a drop of liquid?
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Yeah, I was surprised as well. Though it makes sense if you think about it, since the gas is actually dissolved in the liquid.

I take about half an ounce sample, put it into an old White Labs yeast vial, and shake the hell out of it for a few seconds. Then, I take a drop or two from that.
 
I just did a pretty thorough search of the web, and I can't find any information on the effects of c02 on the refractive index. I did find this website. Which says A refractometer with ATC (Auto Thermal Compensation) is unaffected by temperature or fermentation gases. Where did you get your information? Can you site some sources?
 
Sulli said:
I just did a pretty thorough search of the web, and I can't find any information on the effects of c02 on the refractive index. I did find this website. Which says A refractometer with ATC (Auto Thermal Compensation) is unaffected by temperature or fermentation gases. Where did you get your information? Can you site some sources?
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It's something that a few of the guys mention when people complain about the discrepancy between the logarithm-compensated refractometer reading vs. what they measure with a hydrometer. For both measurements, you need to have a degassed sample in order to get an accurate reading. I'll search around and see if I can find some specific examples for you.

In the mean time, if you've got a small container like a clean film canister or something (I know...what's this "film" thing I speak of?), take a small sample, and measure the difference between right out of the fermenter and after it's been shaken for a few seconds. If there's no difference, no harm done.
 
Sulli said:
Also found this. Thoughts?
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I'm not as well versed in physics as I'd like to be, so I'm not sure how to interpret that paper. It seems that they are looking more at the discrepancies in air densities, factoring in pressure, CO2, and moisture content. I'm not sure that it would necessarily apply to gases dissolved in a liquid medium, but I honestly have no idea. :drunk:
 
GNBrews said:
It's something that a few of the guys mention when people complain about the discrepancy between the logarithm-compensated refractometer reading vs. what they measure with a hydrometer. For both measurements, you need to have a degassed sample in order to get an accurate reading. I'll search around and see if I can find some specific examples for you.

In the mean time, if you've got a small container like a clean film canister or something (I know...what's this "film" thing I speak of?), take a small sample, and measure the difference between right out of the fermenter and after it's been shaken for a few seconds. If there's no difference, no harm done.
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Will do. Thanks.
BTW, I still have a circa 1970's Olympus OM-1; makes a nice paper weight. :D
 
I'm interested in this as well, I wonder how it would effect a lager fermentation.
 
My thinking on lagers is that stirring during the lagering period would increase the yeast to beer surface area, hence doing the same thing Budweiser does with the beechwood chips. What I love about this thread is how the OP is using it during primary. I am excited to even think about the additions that could occur during my pressurized fermentation. Sorry for the plug, but I think it could be discussed. When I do a P-ferment in a Sanke, I am alleviating some of the krausen height due to pressure anyway. With a stir going on, and the addition of Fermcap in conjunction with the benefits of pressure, I am seeing the possibility of even more volume in the primary fermentor. Now, take the fact that I am naturally carbonated before I transfer (all in a atmosphere free environment), and I should leave the bulk of primary yeast behind. If I were to put a stir-bar in my secondary/lagering keg, I should have plenty of yeasties swirling about to clean up the lager very quickly. Can you tell how pumped I am from this dude's thread? Can you? LOL
 
WortMonger said:
Any more updates? I have been anxiously awaiting more taste tests and information about the batches.
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As a matter of fact...I had another tasting party Friday night, and I got to taste a Sierra Nevada beer I've never even heard of; it was called Ruthless Rye, and it was quite delicious. [In fact it's the first rye beer I've tasted; I definitely see a homebrewed rye beer in my future]
The Stone Clones are now residing happily in their kegs; this time around each one had it's own distinct flavor profile. Of the two that were in unstirred carboys, one of them had a hint of diacetyl and tasted just a little off, I'm hoping it will still clean up some in the keg; the other tasted clean and had great hop aroma.
The carboy that was stirred, was excellent; clean as could be, with a nice smooth bitterness, a very balanced profile, and a great nose.
The conical, tasted very dry, and the bitterness was a little harsh, but I couldn't detect any off flavors, it was quite good.
All the carboys had a final gravity of 1.014; interestingly though, the conical finished out at 1.011, this is probably one of the reasons the bitterness tastes a little harsher.
To sum up, the stirred ferment is the clear winner here, in fact it I would say all it needs is some CO2 and 24 hrs in the kegerator, and it's good to go.
The others would do better with a couple more weeks of aging.
I'm extremely pleased with the result of this experiment, and plan on doing more stirred fermentations.
@Wortmonger: I look forward to hearing about your future experimentation with pressure-stirred-fermentation, good luck. :mug:
 
Reading about this experiment, I just get more and more questions. I see your keeping the yeast in suspension longer, and you are degassing all the time(stirring) so less co2 in suspension. Now add stirred fermentation under pressure to the mix.
Hope you both keep great notes and Post them.
 
WortMonger said:
Did you do a D-rest? I think slightly higher than fermentation temp would have taken care of cleaning up the diacetyl.
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I did. After the first week of fermentation, I bumped the temp up to 74 degrees which they sat at for another week. Then I dry hopped them at that temp for an additional week. For some reason just that one carboy wasn't quite cleaned up. I'm going to leave it in the keg at room temp for a couple more weeks, it should clean up just fine.
 
This thread inspired me to try this.. was thinking about it but just have not gotten around to doing it.

cbGIuaGG


My stir setup with a 1.5" bar and 5 gallons of water. Quite surprised a vortex of this size shows up!
 
Satisfaction said:
This thread inspired me to try this.. was thinking about it but just have not gotten around to doing it.

cbGIuaGG


My stir setup with a 1.5" bar and 5 gallons of water. Quite surprised a vortex of this size shows up!
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Excellent! Let us know how it turns out.
 
Sulli said:
The only real difference was one of them had a slight buttery [diacetyl] flavor, but essentially, yeah.
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I just don't understand how two carboys containing exactly the same everything could come out differently unless you did something different. I think you said before that you pitched the yeast after you moved the wort to the fermentation containers. Is this right?

If so, there must be a discrepancy in your pitch rates. I can't think of anything else that would cause the two unstirred carboys to come out tasting different.
 
Yeah, I agree, it's weird. I was very careful in measuring my slurry; the entire slurry was contained in a 1000 ml Nalgene bottle, I just poured 200 ml into each 5 gallon volume, shaking it well between pours, of course.

The diacetyl is pretty subtle though, it's not like it's a butter bomb or anything like that.
 

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