Constant Stirring During Fermentation, Anyone?

I was just reading a post on another topic and the brewer mentioned that he would give his fermenter a swirl once in awhile during fermentation. That got me wondering: what if you put your fermenter on a big stir plate and constantly stirred during fermentation? (You'd probably stop stirring after primary fermentation winds down to let the yeast flocculate.) I wonder how this would change the beer. Has anyone tried it?

I'm not sure that you'd get much of any thing out of it. The purpose of stirring when making starters is to keep introducing oxygen, but that wouldn't be desirable during fermentation. It might help keep yeast from floccing out if you're having difficulty hitting your attenuation. Under normal circumstances, though, I don't think it would help any.

If your yeast is working, it will be stirring up the brew all on its own. It won't need your help. Make sure you aerate it before you pitch the yeast, plop the yeast in and walk away. Don't bother the yeast until its done with its job.

It would oxidize the beer and ruin it. It's fine to aerate at the beginning, but oxidation will happen quickly once fermentation slows.

Triples said:

I was just reading a post on another topic and the brewer mentioned that he would give his fermenter a swirl once in awhile during fermentation. That got me wondering: what if you put your fermenter on a big stir plate and constantly stirred during fermentation? (You'd probably stop stirring after primary fermentation winds down to let the yeast flocculate.) I wonder how this would change the beer. Has anyone tried it?

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If you get oxygen in the fermenter during fermentation while you are constantly stirring it, it will change the beer all right, more than likely make liquid cardboard. Oxygen DURING fermentation is not good.
There's several threads bringing this up, and the answer is the same, greater risk of oxydizing the beer.

The yeast are pretty adept at finding the sugars on their own, ESPECIALLY if you gave them plenty of oxygen BEFORE hand. They done need to have to ride a merry go round while they are doing their jobs.

So it seems like no one who replied has tried it. I don't understand the concern about aeration - the fermenter is full of CO2 as soon as fermentation starts. The yeast keep things moving by themselves pretty well but still a yeast cake begins to form early in the process. The idea is not to aerate but to keep the yeast from settling out so soon. Perhaps we could pitch less yeast and still produce good beer if we kept it stirred up for the first few days. Perhaps it would create a cleaner tasting beer. I just might give it a whirl (so to speak).

Triples said:

So it seems like no one who replied has tried it. I don't understand the concern about aeration - the fermenter is full of CO2 as soon as fermentation starts. The yeast keep things moving by themselves pretty well but still a yeast cake begins to form early in the process. The idea is not to aerate but to keep the yeast from settling out so soon. Perhaps we could pitch less yeast and still produce good beer if we kept it stirred up for the first few days. Perhaps it would create a cleaner tasting beer. I just might give it a whirl (so to speak).

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Go ahead and try it, get back to us with the results.

Triples said:

So it seems like no one who replied has tried it. I don't understand the concern about aeration - the fermenter is full of CO2 as soon as fermentation starts. The yeast keep things moving by themselves pretty well but still a yeast cake begins to form early in the process. The idea is not to aerate but to keep the yeast from settling out so soon. Perhaps we could pitch less yeast and still produce good beer if we kept it stirred up for the first few days. Perhaps it would create a cleaner tasting beer. I just might give it a whirl (so to speak).

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Certainly give it a shot. I would never want to discourage someone from trying something, especially when it's something I haven't tried myself.

That said, there's a reason people are skeptical. You are correct that you won't oxidize your beer if it is sealed off. But, the idea that you'll get a more attentive yeast or cleaner beer doesn't fit with my understanding of the process. Yeast don't flocculate out for lack of mechanical agitation but because of an electrostatic change in their cell walls. This change is trigged by changes in the nutritional contents of your wort. Stirring won't stop that, and you'll just be agitating big clumps of (relatively) dormant cells.

I have heard big brewers laugh about HSA, but always heard mostly the same thing about oxygenation during fementation. I believe that most apply a maxim of none, when sure some would be ok. The question is just are you adept enough to know or make sure you don't oxygenate.

There are many beers that introduce bacteria on purpose in open fermentations (lambics and such), and many Belgian, English, German, and some American breweries ferment even non lambic type beers openly. They stir sometimes depending on yeast flocculance and taste they are going for with the beer. I don't plan on stirring heavily but I do want to do a few open fermentation recipes, as some recipes for some beers I really like call for it. I like estery beers, and more Belgian styles, so we'll see, but I'm a bit afraid, so I've been waiting.

I think thats what Revvy and some of the others meant, can you and produce a great product? Sure, there are actually many breweries that do, but if you do just great without the risk, why include the risk?

if its a big beer... i remember reading somewhere that some brews will need more sugar and o2 mid fermentation just to keep a healthy fermentation going. but who knows where I read that...

i just gave advice on another thread stating to shake up a stuck ferm. doing so will prob add some oxygen, but assuming the yeast are missing oxygen it should not be too much of an issue regarding oxidation.

I don't know if this helps, but on my last 1 gallon starter, I decided to experiment with making beer out of the liquid. It was WY2112





The hops ended up in the 1st glass but I used a metal screen to fix that. It tasted perfectly fine in fact very good for what it was. The blond maltyness was very flavorful and crisp.

I heard of a guy doing this once, but I do not know how the beer came out.

Since CO2 suppressed ester formation you may get more yeast character.The aggitation would result in less dissolved CO2.

Why anyone would think this would result in oxidation in a closed system is a bit strange.

I did this with a 1gal batch of super saison, fermented out to 11% with 3711 in just 3 days. Tasted fine, late hopped Citra so it kind of overwhelmed most of the yeast character (not that 3711 is really that pronounced on yeast flavour). There was really no way for oxygen to get in, the airlock was constantly pushing out co2.

You can certainly stir without oxygenating and I know at least one prominant brewer that rouses daily, just like in wine making, and turns out wonderful product.

If you are able to stir at very low RPM in a semi-closed system there would not be any oxygen introduced. Keeping yeast in suspension seems like a good thing. Since it is routinely done in wine making it makes sense in beer making also, the main difference being the pH's of the fermenting liquor (wine 3.2-3.7, beer 5-6), this makes beer more suseptible to infection (than wine) but the yeast is the same organism and it really doesn't know or care about the end product (beer or wine).

Triples said:

I was just reading a post on another topic and the brewer mentioned that he would give his fermenter a swirl once in awhile during fermentation. That got me wondering: what if you put your fermenter on a big stir plate and constantly stirred during fermentation? (You'd probably stop stirring after primary fermentation winds down to let the yeast flocculate.) I wonder how this would change the beer. Has anyone tried it?

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It would be beneficial during lag and growth, but once you reach the krausen phase I don't see how it would help any.

I recently agitated a NB Tripel that had slowed to 4 bubbles a minute after three days of vigorous fermentation. I decided to move it to another floor in my house and agitated it greatly on the way up the stairs. All of the krausen was lost back into the beer during the move. After two hours the krausen had reformed and CO2 production increased about 4 times. 12 hours later the krausen had grown so much that I had to add a blow off tube. Swirling definately increased yeast in suspension and CO2 production.

I will have to wait to see if this technique had any negative effects.

I took the lid off of a bucket about 2 weeks after it had fermented, used a big spoon an stirred the hell out of it, yeast cake was broke up floatin around and all. Bottle it 2 days later and the beer tasted just fine. Not sure if I got lucky or what but no ill effects. This was when I was still semi new to brewing and I would NOT do it again and take a chance of ruining a batch. All seems to go well if you let it sit and do it's thing.

I'm no expert, but I am a confirmed swirler, and I have yet to detect any off flavors as a result.

And before the first person jumps in to claim I am "oxidizing" my beer, I ask, with what oxygen? Whatever O2 was once in the carboy has long since been replaced and pushed out through the airlock by CO2 before I swirl the carboy.

mightynintendo said:

...there should be little reason for concern as long as there is active fermentation going on and there is no chance outside air is getting inside the container.

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Found this here

There is even a youtube of the Carboy Stir Plate. I have no opinion on the subject....

I brewed a batch of Imperial Pale Ale Sunday...finished about 6pm with US-05. Re hydrated per instructions, pitched @ 66 degrees. Capped it up.
Ambient temp of 66-68... Tuesday, still no activity. I left it alone as I read here, thinking that things were ok inside. Wednsday, almost 72 hrs later no airlock activity..gave it a swirl..moved to a 2 degree warmer spot and POW! Now 30 hrs later , thick Krausen formed and all seems good. Was it the swirl?? Not sure but it seemed to help things along.
Moved it back to a cooler location and fingers will be crossed.