Why not use a stir plate in fermentation?

I just did my first starter using a stirplate. It got me thinking - if it could be rigged up so it would work, why not use a stir plate during primary and keep the yeast moving around a bit more? Seems like you would ferment faster and perhaps get more attenuation. Any reason why not other than the task of getting a fermenter to sit on top of a stirplate?

 

Most of my primary fermentations look like they ARE on a stirplate. I think the question is if it's really even necessary given the agitation of fermentation itself.

 

Biggest reason is that it would more than likely oxydize your beer. Part of the role of a stirplate is to help oxygen absorbsion for the yeast in the beginning so they reproduce...oxygen in fermenting beer is bad.

This has been brought up several times...here's one discussion.

Why don't we agitate during fermentation?

 

I believe one of the main reasons a stir plate is used is to help oxygenate the starter wort to enhance reproduction of the yeast. Once reproduction is over, though, you don't want any further oxygen in the wort. This may be one reason against it.

Also, as klyph said, my wort tends to churn quite a bit during fermentation.

 

I wouldn't think oxidation would be too big of an issue actually. As long as you know you have an air-tight system (glass carboy with a full air-lock should ensure that), there's no risk of oxidizing your beer by stirring it. The oxygen that's in there is a small amount and will be getting pushed out rapidly by CO2 once active fermentation starts.

The better reason is that 95% of the time, it would be unnecessary. I could definitely see some benefits of using a stir bar if you were doing big beers and wanted to plan for the inevitable re-rousing of the yeast. I have a friend who used to use this method with a lot of success.

 

This thread again?

If your fermenter is sealed, and I assume it is, there is zero risk of oxidation.

Stirring the yeast during fermentation/conditioning would be especially helpful for highly flocculent yeast strains that tend to settle too early.

 

this seems to me to be one of those topics where intuition and science are going to conflict. I bet using a stir bar during primary fermentation does nothing to your attenuation. The yeast are going to convert what the yeast will convert. Agitation will not impact their "diet".

You may impact the speed of the fermentation a little, but I let my primary sit for a month no matter what so this would be of no help to my process.

One of the benefits to stirring the starter i that it helps to off-gas CO2 as high concentrations of CO2 can slow reproduction. however, once you have pitched the correct number of yeast into your fermentation tank this issue is moot because you already have enough yeast cells.

 

I don't mean to beat a dead post with a sick, but has anyone ever tried to do a controlled test? It would be interesting to see the results, but as Revvy posted in the other post, why change something that isn't broken.

Still I do like to see/read results of experiments!

 

If you have the desire/means/time to do a controlled test for this question, you'd be far ahead of the game and could give people some feedback.

There's a definite chance you could speed up the fermentation, and I think there's little chance you'll do any harm in terms of oxidation.

So when should we expect the results of your test?

 

I saw what you did there. Very smooth!

I knew immediately that he would get the job.

 

As soon as I can get to making a stir plate! But, I hardly have time now a days to even brew.... but if i do get around to doing experiments I will keep you all posted!