Stir plate for fermenter?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

BrewclearAssault

Well-Known Member
Joined
Sep 27, 2010
Messages
63
Reaction score
2
Location
Appleton
Hey guys, my imagination was running wild again recently, this time through the fields of yeast starters, fermentation, and the combinations thereof.

A few batches ago, I started using yeast starters because I was told it was a great way to improve your beer. That held true. With my most recent batch, I assembled a stir plate that seems to have done it's job quite well, and I'm hoping for another jump up in quality for this batch.

My question though, is would using the stir plate during the primary fermentation multiply the yeast more and thus, give me even better beer? Or is this just wishful thinking?
 
Absolutely do NOT use the stir plate for your beer.

If you really want to see what it would do, take a 1/4 cup or so of the yeast cake when you finish this batch and make up another starter with it. Give it a couple days, chill, and decant the liquid into a glass. After 1 sip, I'm sure you'll never want to brew a whole batch that way.
 
Sounds like fun--I'm imagining a stirplate that's maybe 20" across...on second thought, maybe a little too much fun.

However, if you want more yeast, the easier way would be to oxygenate (not simply aerate) your beer. Buy a wand and a tank of 02, and you'll get more yeast than you could ever hope to use.
 
Ah, that makes perfect sense. I was working off of the notion of "rousing" the yeast so that it doesn't settle so much. Thanks a lot!
 
Haha bill I'm gonna try that just for the hell of it, but I believe you! And I'll have to look into oxygenating my beer in the future, that sounds like a tempting idea.
 
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.

Here is another abstract:
"...Much less intense mechanical agitation also decreases batch fermentation time for anaerobic beer production by about 25% compared to mixing by CO(2) evolution alone with a small change in the concentration of the different flavour compounds. These changes probably arise for two reasons. Firstly, the agitation increases the relative velocity and the area of contact between the cells and the wort, thereby enhancing the rate of mass transfer to and from the cells. Secondly, the agitation eliminates spatial variations in both yeast concentration and temperature, thus ensuring that the cells are maintained close to the optimum temperature profile during the whole of the fermentation time. These bench scale studies have recently been supported by results at the commercial scale from mixing by an impeller or by a rotary jet head, giving more consistent production without changes in final flavour. It is suggested that this reluctance of the brewing industry to use (adequate) mechanical agitation is another example where the myth of shear damage has had a detrimental effect on the optimal operation of commercial bioprocessing."

We would be better off if we had a means to keep the wort moving and the yeast in suspension...it's just difficult for the homebrewer and sanitation becomes the primary concern.
 
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.

Yes! And, in absolute fact, oxygen is never actually good during our processes.

Oxygenation is never a positive for the wort.

Yeast need the O2 to produce some fatty acids so they can reproduce, but we sacrifice the O2 combining with everything else in our wort to make the yeast happy.

It's a trade. MORE O2 is not the goal. That's bad. Enough O2 is better, but no O2 and another supply of fatty acids would be better. Hence the efforts to use other sources (olive oil, etc).

Cheers
 
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A few years ago I became interested in such reports and decided to try it out on a small scale. I made a stir plate large enough to agitate a 6 gal carboy as long as fermentation was taking place. In my experience, the fermentation is shorter and more consistent between batches than what I was getting before agitation. here's my rig...

4_gal-33887.jpg

Cheers..
 
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.

Here is another abstract:
"...Much less intense mechanical agitation also decreases batch fermentation time for anaerobic beer production by about 25% compared to mixing by CO(2) evolution alone with a small change in the concentration of the different flavour compounds. These changes probably arise for two reasons. Firstly, the agitation increases the relative velocity and the area of contact between the cells and the wort, thereby enhancing the rate of mass transfer to and from the cells. Secondly, the agitation eliminates spatial variations in both yeast concentration and temperature, thus ensuring that the cells are maintained close to the optimum temperature profile during the whole of the fermentation time. These bench scale studies have recently been supported by results at the commercial scale from mixing by an impeller or by a rotary jet head, giving more consistent production without changes in final flavour. It is suggested that this reluctance of the brewing industry to use (adequate) mechanical agitation is another example where the myth of shear damage has had a detrimental effect on the optimal operation of commercial bioprocessing."

We would be better off if we had a means to keep the wort moving and the yeast in suspension...it's just difficult for the homebrewer and sanitation becomes the primary concern.

Great post; thanks for the info.
 
Sudbuster could you post more info on your build and process for stirring? Also how does the krausen look during fermentation, does it make it blow off easier? I'm super jealous, I'll have to try making this myself.
 
Doesn't the airlock keep oxygen from getting in? If there was an airlock attached and a stir plate in operation, that would keep the yeast in suspension while keeping the O2 out, would it not?
 
Okay, I don't feel like such a dork now. I have a 5.5Gallon graham cracker ale that should be ready to be kegged tomorrow that I fermented on a stir plate. The fermentation was something to behold. ACTIVE fermentation only took about 3 days. But it seemed that the agitation actually reduced the krausen, even with a haze of bubbles rising constantly it never grew above about 1". A blow off is definitely required for those first 3 days though!!
As for comments about the flavor profile changing I don't have a reference as this was a new recipe for me.
But if I can ferment to FG in a week I'm a convert.
 
I did a 1 gal extract tripel yesterday and put the fermenter on my stirplate on low speed to see what happens. I really don't see how stirring can have anything other than a positive effect. Reducing yeast sedimentation, improving yeast-wort contact, and increasing wort-to-headspace contact to aid driving out dissolved CO2 are all desirable effects. There will be no oxidation due to the airlock. The Teflon coated stir bar was boiled and then StarSan'd. I pitch at an appropriate rate and on big beers oxygenate with 100% O2 just prior to pitch and again at 12 hours. I was concerned about shear stress on the yeast and whether that would cause lysis, but some of the references posted above state that has not been an issue. We will see.

Question is how long to stir. I generally go 1 month in the primary (no secondary) and then to bottle for as long as I can stand it. I'll probably stop stirring after 3 weeks to let the dust settle.

I feel this hobby is all about experimentation, and I am not going to let the fearmongers keep me from doing so.
 
I did a 1 gal extract tripel yesterday and put the fermenter on my stirplate on low speed to see what happens. I really don't see how stirring can have anything other than a positive effect. Reducing yeast sedimentation, improving yeast-wort contact, and increasing wort-to-headspace contact to aid driving out dissolved CO2 are all desirable effects. There will be no oxidation due to the airlock. The Teflon coated stir bar was boiled and then StarSan'd. I pitch at an appropriate rate and on big beers oxygenate with 100% O2 just prior to pitch and again at 12 hours. I was concerned about shear stress on the yeast and whether that would cause lysis, but some of the references posted above state that has not been an issue. We will see.

Question is how long to stir. I generally go 1 month in the primary (no secondary) and then to bottle for as long as I can stand it. I'll probably stop stirring after 3 weeks to let the dust settle.

I feel this hobby is all about experimentation, and I am not going to let the fearmongers keep me from doing so.

I have been very curious about this because I have read about rousing yeast in traditional production of high-gravity beers. Ray Daniels talks about how English brewers used to take the beer for a walk when they were making barley wines. I still haven't heard a reason to believe that it could be harmful, at any rate, so let us know how it goes.
 
Hmmm... Something is strange. OG was 1.085 and recipe had 20% sucrose (sucrose added on day 2) and had vigorous fermentation blowing out my stopper and blowoff hose. MrMalty pitch rate with fresh yeast, O2 injected at pitch and 12 hours later. Fermentation slowed after a week (about a bubble/minin the airlock), but then kept bubbling at this rate.

Kept it stirring and checked on day 22 and was 1.027 and very sweet. Checked again on day 25 and was 1.025. Evidence points to continued slow fermentation...I would have really thought the stirring would have sped things up quite a bit more.

Unfortunately I have introduced another variable here though. Normally start ferment at 66F in the basement and bring upstairs into a cupboard the wife lets me hide it in to finish things out at 71F. Well, stirplate and jug don't fit! So, this batch was kept downstairs at 66F the whole time, and I would guess the stirring helped equalize temperature and reduce the normal internal temp increase seen during vigorous fermentation. So, overall a much cooler ferment.

I'll just wait it out and see where it finishes. It'll be done when it's done.
 
So after 5 weeks on the stirplate went from 1.085 to 1.015 with WLP530 kept at 66-67 F ambient the whole time. Not too bad for extract (Briess Pilsen Light DME). Tastes no different than without stirring. Will see how it turns out after it carbs and conditions a bit.
 
Back
Top