Happy HolidaySs Giveaway - Last Sponsor Giveaway of the Year!

Come Enter the BrewDeals/FastFerment Giveaway!


Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Why don't we agitate during fermentation?
Reply
 
LinkBack Thread Tools
Old 10-30-2009, 09:37 PM   #31
springer
Feedback Score: 0 reviews
 
springer's Avatar
Recipes 
 
Join Date: Feb 2008
Location: Wappingers falls NY
Posts: 4,990
Liked 20 Times on 19 Posts

Default

I have to say the quality of his products is top notch. If it works out for me I will have to buy a few more . I have two 1/2 barrels and three 1/4 that I want to use as fermenters . I already used the 1/2 a few times but with a stopper and airstop

__________________

'The taxpayer: That's someone who works for the federal government but doesn't have to take the civil service examination.'- Ronald Reagan

springer is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 09:37 PM   #32
Edcculus
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jun 2007
Location: Greenville, SC
Posts: 4,567
Liked 41 Times on 38 Posts

Default

Quote:
Originally Posted by springer View Post
wasn't walking the barrel used towards the end of fermentation? Just like when I swirl the carboy a few days after active fermentation is complete just to rouse the yeast a little .

And conditioning is done after the active fermentation is completed.

I asked why do it during an active fermentation . Because the yeast are doing a pretty good job of it on their own.
Oh, I thought you were talking about rousing at the end of fermentation. I don't claim to be an expert, but it seems to me if you pitch enough yeast, using a stir plate for a whole batch is probably useless. That is unless you are trying to achieve a very specific goal, like a really dry beer with no adjuncts.

I also know we can't compare everything we do to commercial brewers, but you don't see them mixing up thier fermenting wort. I guess I'm trying to say that I don't fully understand the point of this. Why would I want to constantly stir my fermenting wort when I can get desired attenuation through proper aeration and pitch rates?
__________________
Edcculus is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 09:41 PM   #33
david_42
Feedback Score: 0 reviews
 
david_42's Avatar
Recipes 
 
Join Date: Oct 2005
Location: Willamina & Oak Grove, Oregon, USA
Posts: 25,656
Liked 136 Times on 129 Posts

Default

Quote:
Even if the top of a flask is left completely open (rarely the case) how is the oxygen getting in there once it is full of co2?
Two reasons: 1. air-entrainment due to friction 2. yeast give off very little CO2 during their growth.
__________________

Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

david_42 is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 09:56 PM   #34
Bonysplicer
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2009
Location: Reading, Pennsylvania
Posts: 8
Liked 1 Times on 1 Posts

Default

Quote:
Originally Posted by Revvy View Post
I'd like to see it done both on a closed setup like yours, but also done in a typical carboy/airlock setup that most folks have. I have a feeling the results would be quite different. That perhaps in a closed environment, purged of o2 it would work great, and their would be no oxydation worries...but in a "real world" or typical hb'ers situation it would be a setup for disaster.
Your statement shows a lack of understanding of physical chemistry. Check out references to Henry's Law. In any fermenter situation, carboy or otherwise, gases exist in equilibrium between two phases, gaseous (headspace) and dissolved gas in solution. the rate of transfer in this equilibrium is a surface area limited function.

For example, when you use an oxygen stone or fish tank bubbler to pump o2 through your wort, the wort picks us a high level of o2 quickly due to surface area to volume ratios of tiny bubbles and the high partial pressure of o2. Similarly, boiled, degased starter wort picks up oxygen because whirlpool agitation increases surface area exposure, but still the wort will only dissolve enough o2 gas to be in equilibrium with the partial pressure of o2 in the headspace. So relative to the gas/liquid interface stirring merely hastens the balance of equilibrium.

BUT in a fermenter yeast use o2 and "fart out" co2 into solution So the partial pressure of dissolved o2 decreases over time and the partial pressure of co2 increases over time. Additionally, the total pressure in the headspace is regulated by the airlock/blow off. So as the co2 builds up in solution it increases the partial pressure of gaseous co2 (equilibrium). But since the total pressure is fixed, gas is driven off through the airlock. That gas is a mixture of co2 and o2. Over time the faction o2 in the headspace limits toward zero through being driven off through airlock and being used by the yeast.

My understanding is that "oxidation flavors" are caused by excess dissolved o2. From this it would seem prudent to drive off excess dissolved oxygen as quickly as possible, prehaps through agitation in an oxygen defficient environment.
__________________
Bonysplicer is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 10:18 PM   #35
lamarguy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2008
Location: Austin, TX
Posts: 1,657
Liked 21 Times on 20 Posts
Likes Given: 1

Default

Quote:
Originally Posted by Edcculus View Post
Why would I want to constantly stir my fermenting wort when I can get desired attenuation through proper aeration and pitch rates?
The objective is maximize the movement of the yeast throughout the wort. A stir plate is an effective means to achieve constant yeast movement. The secondary objective is to speed the conditioning process.

For example, studies have shown leaving cold break in the fermenter increases the nucleation sites for CO2 during active fermentation, which allows the CO2 to be released more readily from solution. This induces stronger currents (swirling) within the wort, a "natural" method for yeast movement. We're just talking about augmenting that process with mechanical motion.
__________________
Doggfather Brewery

Planned: Lambic, American IPA
Fermenting: 6 gals of 1.090 stout (Belgian) & 6 gals of 1.090 stout (English)
Tapped: Berliner Weisse, Black English IPA, German Pils, & Live Oak Primus
lamarguy is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 10:21 PM   #36
wildwest450
Feedback Score: 0 reviews
Recipes 
 
Join Date: Dec 2007
Posts: 9,099
Liked 166 Times on 151 Posts
Likes Given: 4

Default

Quote:
Originally Posted by Bonysplicer View Post
Ah! It's not a matter of disliking your explanation! I certainly did not mean to offend. I was just looking for a bit more of a scientific explanation than "Oxidized beer is not yummy" I was merely conjecturing and offering my thoughts on the situation
Then go talk to a scientist, this board is to give advice, not provide you with "scientific" explanations of everything. I've brewed enough beer to know you don't want to put your carboy on a stir plate.

But please, feel free to do so and report back with the results.
__________________
wildwest450 is offline
 
Reply With Quote Quick reply to this message
Old 10-30-2009, 11:20 PM   #37
oldschool
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2009
Location: southern IN
Posts: 738
Liked 3 Times on 3 Posts
Likes Given: 1

Default

Quote:
Originally Posted by JVD_X View Post
A fermenter is not a closed system, it out-gases.

Also, O2 CAN come back the other way if the pressure on the outside exceeds the pressure on the inside. This happens most often when you put an airlock on while the wort is still warm.
Maybe slightly..but not for long. The wort will start to outgas and form a CO2 blanket over the beer since it is heavier than the O2. I respect the Rev's opinions but sometimes i wish someone would say "I'm not sure, I have not tried that sort of thing. You should try it and educate all of us." I once posted a thread basically saying that, "here is what i did, these are my results" and almost everyone told me that i had to be wrong.
__________________

oldschool is offline
 
Reply With Quote Quick reply to this message
Old 10-31-2009, 12:42 AM   #38
Revvy
Post Hoc Ergo Propter Hoc
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Revvy's Avatar
Recipes 
 
Join Date: Dec 2007
Location: "Detroitish" Michigan
Posts: 40,804
Liked 2767 Times on 1657 Posts
Likes Given: 3485

Default

Quote:
Originally Posted by oldschool View Post
I respect the Rev's opinions but sometimes i wish someone would say "I'm not sure, I have not tried that sort of thing. You should try it and educate all of us."
Uh, I think I said that, TWICE in this thread....

Quote:
Originally Posted by Revvy
If you don't like our explanation, and have your own theory then why don't you try it and prove us wrong? Me personally, I don't want to risk 5 gallons of beer to know if I am wrong or not.
Quote:
Originally Posted by Revvy
Then YOU do it...make up a 10 gallon batch of beer....split it into two fermenters, pitch EXACTLY one packet of dry yeast into each batch....Spin one with a stirbar, leave the other alone. Bottle and come back in 6 weeks and see if half the batch tastes like cardboard.


Actually THREE times, I also discussed Larmarguy's experiment and offer some ideas as to that as well.
__________________

Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

Revvy is offline
 
Reply With Quote Quick reply to this message
Old 10-31-2009, 02:33 AM   #39
JKoravos
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2009
Location: Chelmsford, MA
Posts: 964
Liked 18 Times on 14 Posts
Likes Given: 3

Default

I've been thinking of adding agitation to my next fermenter. I don't see any reason that it would have anything other than a positive affect on the fermentation. The agitation doesn't need to be terribly vigorous and probably not even continuous to get maximum attenuation out of the yeast. You'd likely have to adjust your brewing process a bit for slightly higher attenuation, but in the long run it's probably an extremely consistent fermentation method.

Oxidation shouldn't be a concern at all. I'm not sure why it would be, there's no oxygen in there.

__________________
JKoravos is offline
 
Reply With Quote Quick reply to this message
Old 10-31-2009, 03:05 AM   #40
remilard
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2008
Location: Kansas City
Posts: 3,655
Liked 39 Times on 38 Posts

Default

Quote:
Originally Posted by wildwest450 View Post
I've brewed enough beer to know you don't want to put your carboy on a stir plate.
How can you know something when you lack anecdotal observation or even a rudimentary understanding of why it would be true?

Bonysplicer has a point in that the oxidation argument, that is stated as a matter of fact, is laughable. It blows me away that somebody can think that agitating the beer would change the composition, apparently via magic, of the gas that is in contact with the surface. It certain would change the surface area exposed to gas, but that doesn't matter if all of the gas is inert (as it was right before the magic happened).

Also laughable, that two HBT posters with more street cred than Bonysplicer are doing the same damn thing and nobody is calling them stupid.

My 2 cents, I think recirculating the beer with a pump is a more promising approach (and one practiced by a number of commercial breweries).

My other 2 cents, this is the wrong message board to use the word "why" on.
__________________
remilard is offline
 
Reply With Quote Quick reply to this message
Reply



Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wine fermentation vs beer fermentation Tophe Wine Making Forum 4 11-19-2010 07:38 PM
Which is better? A fast, very active fermentation, or a slow steady fermentation? cerberus9 Beginners Beer Brewing Forum 6 09-24-2009 05:56 PM
Fermentation cooler vs refrigerator vs son of fermentation Belmont General Techniques 14 04-10-2009 01:43 PM
Stuck fermentation...finished fermentation...? arover Beginners Beer Brewing Forum 3 04-08-2009 04:05 AM
Should I agitate the bottles? alee Beginners Beer Brewing Forum 13 02-12-2009 11:51 PM



Newest Threads

Ok?

LATEST SPONSOR DEALS