aeration of wort by bubblers

[BradyJ]

How many homebrewers use the fishtank bubbler gadgets advertised around to get extra air in the wort during the first part of fermentaion.

If used, how long is it done, and when would it cause excessive
oxidation of the wort

[toneyc]

The homebrew shops sell a stainless steel version of that for use with oxygen or a fish tank air pump. If you're using the fish tank pump, you might consider using a sterile filter, and aerate for 8-10 minutes. If you're using oxygen, 30 seconds to a minute is all ya need.

:)
Toney.

[HarkJohnny]

BYO has a great article this month on aeration along with some tips and build-it-yourself stuff. worth a read

[Mad Scientist]

I used a stainless beer stones. i like to aerate for about twenty minutes for a lower gravity wort, but as much a I possibly can for high gravity sutff. watch out for the foam...no way around it...

[BradyJ]

For worts over 1.05 or so, you say you aerate as much as possible with the stainless beer stone. Do you do it for days???

Thanks,BJ

[Mad Scientist]

No, I think the longest has been about an hour and 15 minutes, but that time, the foam is unmanageable

[stronk]

I think what Brady means is do you leave the aeration system going whilst the brew is fermenting, to which the answer is a resounding 'no'. The oxygen is just there for the initial replication stage of the yeast. Once it has got going, the fermentation is anaerobic (does not use oxygen) and in fact, any oxygen in solution with alcohol will result in ethanoic acid (vinegar).

[BradyJ]

If the anerobic process is what we're after(alcohol), and the aeration is only in the beginning to help the yeast proliferate rapidly, why not just add lot and lots of yeast at the start from a giant starter?? Can you add too much starter?

[Mad Scientist]

That is a good idea, but it is just easier to aerate than to make a massive starter. The only excption that I can think of is when you are re-pitching on top of a freshly vacated yeast cake.

[Mad Scientist]

BTW, I make a starter anyway, usually 500ml w/ 1/2 cup of DME.

[danno]

Originally posted by stronk
...and in fact, any oxygen in solution with alcohol will result in ethanoic acid (vinegar). stronk, I'm gonna call you out on this one... vinegar is the byproduct of an acetobacteria, not oxygen. oxygen introduced once the anaerobic fermentation stage starts gives cardboard flavor...

BradyJ, to answer your second question: theoretically, yes, but it's pretty tough for homebrewers. IIRC you need to be over 20% volume of yeast to be "overpitched"... this info comes from a hazy memory of a Brewing Techniques article where Dr. Fix mentions that a 1 gallon slurry for a 5 gallon batch would be considered overpitching...

[BradyJ]

Originally posted by Boerne Brew
BTW, I make a starter anyway, usually 500ml w/ 1/2 cup of DME.

And do you pitch the whole thing into a 5 gallon batch??
also, is it a 24 hour starter, 48 hour or .....??

I ask because the first starter i made ( 4 days old w/ settlement) took
over 18 hours to get the 5 gal batch going. I thought it would be faster.

[Mad Scientist]

I pitch a 24 hour incubated starter (after the wyeast has had about 12 hours to poof-up). I've thought about waiting 48 hours though.

I usually dump the whole thing in.....

With my 24 hour starter, I have activty within an hour usually

[BradyJ]

[QUOTE]Originally posted by danno
[B]stronk, I'm gonna call you out on this one... vinegar is the byproduct of an acetobacteria, not oxygen. oxygen introduced once the anaerobic fermentation stage starts gives cardboard flavor...

Are you sure? Why does wine turn to vinegar when just exposed to air??

Also my first starter mentioned above, was 1 quart in a gallon jug with airlock. I shook it hard every day to help the yeast grow. At the end of 4 days I pitched mostly the settled yeast, but it smelled and tasted like vinegar some. I was worried it was contaminated so i took it to look under a
good microscope. I couldn't fine any bacteria. and i found some bacteria to look at to make sure I could see them. Lots of yeast though...hugh compared to bacteria. so what caused the vinegar smell?? If not bacteria I thought it might be excessive aeration. remember i started with 3/4 gal of air and 1quart of wort in the jug of starter.

[danno]

let me clarify. acetobacteria are aerobic, meaning they require oxygen to function. oxygen by itself with alcohol will not cause vinegar.

BradyJ, yes I'm sure. why wine changes to vinegar when left open to air? because it's picking up bacteria from the surrounding area.

[deemzzzz]

Originally posted by danno
let me clarify. acetobacteria are aerobic, meaning they require oxygen to function. oxygen by itself with alcohol will not cause vinegar.

BradyJ, yes I'm sure. why wine changes to vinegar when left open to air? because it's picking up bacteria from the surrounding area.

This is true in some places while the bacterias are not right in others. Most winemaking/homebrewing shops will sell the vinegar "mother" which is essentially like buying bateria for Lambics.



As far as aeration - I use welding oxygen. The tank itself costs $8 and has lasted me 7 batches so far (plus my buddies all playing with it when I first got it.) The stone and regulator cost ~$36 from williamsbrewing.com (most stores have them. I like the williamsbrewing one becomes it comes on a rigid metal and is easier to control.) I run it for 60 seconds in a 5 gallon batch and also use a 500 ml starter. (Starter is 500ml in a 1L flask with a homemade stir plate. Ferment for 24 hours, refrigerate for 24 hours - most of the crappy beer poured off and all the yeast into the beer.) Lag times very depending on temperature. First bubble in about 30 minutes. Active bubbling within 1-3 hours.


Greg Doss from Wyeast wrote a really great analysis of oxygenation on AHA's email list. I am reposting it here with the presumption that reposting a properly credited email such as this is is fair use.
---

From: Greg Doss [mailto:Labservices@wyeastlab.com]
Sent: Wednesday, November 02, 2005 12:27 PM
Subject: Re: Oxygenation

This post is in response to some recent discussions regarding oxygenation levels in wort.
We (Wyeast) recommend 8-15 ppm O2 for healthy fermentations. Some strains require higher oxygen levels than others. Manipulation of pitch rates can increase or reduce the need for oxygen levels. High pitch rates lead to fewer doublings and reduce the need for high levels of sterols. Sterol levels are typically the limiting factor in cell growth. These cellular membrane components are synthesized by the cells using oxygen during the lag phase and assist in keeping the membrane flexible and permeable. Low pitching rates lead to an increase in cell growth (doublings) requiring higher levels of sterols and oxygen.

Last year I ran an experiment comparing homebrew oxygenation methods. The experiment compared dissolved oxygenation levels achieved vs. time for homebrew oxygenation methods including splashing and shaking, siphon spray, aquarium pump, and pure oxygen. I presented the results at the NHC last year in Vegas.

Methods Compared:
Splashing and Shaking- Traditional homebrew aeration method of picking up the carboy and shaking it.
Siphon Spray - Small attachment to your run-in hose that splashes the wort as it enters the fermenter.
Aquarium Pump and Stone- Running compressed air from an aquarium pump through a 2 micron stone (Oxynater).
Pure Oxygen- Running Oxygen through a 2 micron stone (Oxynater) at a flow rate of 3.5 LPM.
The same wort and temperature was used for all methods. Dissolved oxygen levels were measures at 5 second intervals using a DO meter.
OG- 1.045
Temp- 68 F
Volume- 5 gal
Fermenter- Standard 5 gal glass carboy
Stone pore size- 2 micron (Liquid Bread Oxynater)
Oxygen Supply- Bernzomatic
Oxygen flow rate with Bernzomatic was estimated at 3.5 LPM based on a visual comparison of stone activities (vigor of bubbles) with a regulator with gauges on a larger cylinder.

Results:
Siphon Spray: Delivered 4 ppm in wort transfer.
Splashing and Shaking: Reached saturation point of 8 ppm in 40 seconds.
Aquarium Pump and Stone: Reached 8 ppm in 5 minutes.
Pure Oxygen with Stone: 8 ppm (20 seconds), 15 ppm (80 seconds), 22 ppm (2 minutes)

Comments:
There are a lot of variables involved with dissolving oxygen into solution including wort gravity, wort temperature, stone pore size and surface area, O2 flow rate, time, turbulence of wort, and fermenter geometry. This experiment attempted to reduce the number of variables. Oxygenation of a large amount of liquid with a small stone is not an efficient way to dissolve O2 into solution, but in most homebrew cases it is the only method available. Oxygenation in-line (professional method) increases surface area and contact time and increases the efficiency of dissolving O2.
That being said, this experiment demonstrated that using an aquarium pump with a stone is not an efficient way to deliver oxygen into wort. Splashing and shaking was rather efficient (40 sec.) in achieving O2 saturation point with air. Pure oxygen is an easy method that not only allows brewers more efficiency and better control over DO levels but also allows brewers to attain higher levels of DO versus using air.

As a side note, I currently use a combination of two methods. I inject a small amount of O2 and then shake my carboy to fully dissolve it into solution. I have not run any tests with this method but am confident that I am achieving good levels of DO.

I hope that this helps. If you want any additional information or a chart on oxygenation levels vs. time using O2, please email me at labservices@wyeastlab.com

Thanks,
Greg

Greg Doss
Microbiologist/ Brewer
Wyeast Laboratories

[zoom6zoom]

Vinegar is acetic acid, is it not?

[BrewDog]

zoom-
Yes, it's acetic acid.

deemzzzz-
Great article. Thanks for posting it.


My memory on this is hazy, but wasn't there a Zymurgy article on this (and it included Hydrogen Peroxide as an aeration method) within the last year or so? I seem to remember some mention of the contribution that Nitrogen made to the taste of the beer in that article. Basically, even though pure O2 is faster, the other methods also introduce nitrogen, which the yeast use, too. I think (again, my memory is hazy) that that article stated that the aquarium pump, while slower, yielded the best tasting finished product.


FWIW, I decant off the liquid, and just pitch the slurry.