Aerating

[KCWortHog]

I had no idea the shaking-aeration method was so vigorous. I thought it was just swirling/rocking, avoiding spillage. I told you I need videos (doesn't really matter, as we have an O2 tank, but I've been wondering about this on principle.)

So, basically, the take-away here is that with vigorous enough activity, the CO2 displacement will be enough to let oxygen in to the carboy. Makes sense.

I'm still skeptical on the leaving-off-the-airlock concept oxidizing mead/beer/cider/etc ONCE the layer of CO2 has been created, but I won't beat that dead horse anymore

 

[ZachR]

As someone mentioned earlier, a layer of CO2 doesn't last long (unless protected from incoming gases by an airlock) because of diffusion. High energy gas molecules are constantly bouncing around, and given enough time, the CO2 will completely "dissolve" in the surrounding air, just as sugar or salt will eventually dissolve in a glass of water even without stirring.

As for aerating wort/must, vigorous shaking (I usually shake carboys for about 10 minutes before I pitch yeast and about 5 after) helps dissolve oxygen from the air into the liquid faster. Gases will still dissolve in the liquid even under atmospheric pressure, but it will be at a much slower rate than shaking.

 

[KCWortHog]

The salt/sugar comparison doesn't really cut it though because both salt & water are more dense than water - so of course they'll fall & dissolve. Here's how I've always thought of it - say oil is air and water is CO2. Put some sand at the bottom of a bowl, then add water, then float oil on top of it - the oil stays put. It doesn't slowly "dissolve" into the water and rest on the sand.

Swirl them around and you get pretty much the same result - some oil might dip below the surface of the water, but it doesn't get to the sand. That's exactly how I've pictured "aerating" mead by swirling. Now, take a whisk to it or shake it and make a mess, and that's a different story.

Oh, and I may be strong for a woman, but I can't shake a 6-gallon carboy for 10 minutes. Those things are heavy!

 

[Medsen Fey]

Instead of oil and water, think ethanol and water. Ethanol is much lighter than water - compare the sp. gr of each. When you pour ethanol on water, the ethanol doesn't float, it mixes in. CO2, nitrogen, O2, argon and other gases mix equally well.

 

[Dan McFeeley]

I think the basic principle fueling gas diffusion is brownian motion -- Medsen already touched on it when he described gas molecules bouncing around in a closed space. Regardless of the weight of the gas, it will spread out occupy all available space, mixing with other gasses, as the individual molecules ricochet all over the place.

An everyday example -- if this didn't happen, the individual gasses in the athmosphere would form layers one on top of the other and there would be no life as we know it.

Aeration -- the shake rattle and roll method works, but it's gotta be really vigorous, with maybe half the volume of the carboy taken up by the must to allow sufficient mixing of the must with air, and even then it's the least efficient method of aerating the must. Although I prefer to use an airstone, I've shook up large batches of JAO just because it's how Joe said to do it. I'll fill half the carboy, using all the honey, shake it up good for a while, then fill up the rest of the carboy with water and swirl to mix it.

--

 

[wildoates]

Also, polar solutions dissolve only into other polar solutions, the same goes for non-polar solutions. That's why oil and water will never "diffuse" without an emulsifier. Substances also must be soluble, which is why sand doesn't dissolve into the water. While it is true that gases have differing densities and denser ones will start out on the bottom, they won't stay there for the very reasons stated.

I used to do (when I taught this stuff) a little demo to illustrate this--I'd spray a fine mist of a very nasty cologne in the far reaches of the classroom without saying anything to anyone. Now, if density was the only issue, since the cologne molecules are heavier than air they should just fall to the floor, but it volatilizes and soon spreads to all corners of the room until the cologne molecules are more-or-less evenly dispersed in the room air.

CO2 does the same thing in a carboy unless the headspace is completely filled up with CO2, all room air is pushed out, and it's then airlocked. It hopefully won't smell as bad as that vile cologne did, though. Ewww.

 

[wildaho]

Adding oxygen to beer once fermentation begins WILL OXIDIZE your beer... {snip}

And FWIW, I think most serious homebrewers have already been "shaken up" by John Palmer, Jamil Zainasheff, Ray Daniels, Greg Noonan, George Fix... those are the names I think most homebrewers have on their shelves these days. Including a dusty copy of Joy of Homebrewing. (and occasional mentions of RDWHAHB )... {snip}

I promise the beer part of this post came out way more cranky than I really intended it to and I've tried to nice it up a bit but I clearly have an opinion on the matter, lol.

KC,

How long have you been brewing? And how much of what you are saying is based upon the books you named and what is your own personal experience? I'm thinking that you are believing the "gospel" of the gurus rather than testing the limits yourself. Palmer and Daniels in particular are little more than a regurgitation of Papazian. Noonan & Fixe were more concentrated on lagers. Jamil is like Oprah, popular, perhaps, but? You couldn't have made my point any better if you tried.

Always question authority. Otherwise you will always be a sheep, rather than the Shepard. We encourage people here to try new things. Open your mind a bit and you might be surprised. But until you try it, you can't deny it based upon other doctrines that you haven't tried either. I hate to bring parallels to religion but...

The figures you name are all estimable. But they are all aiming their procedures around beers that are around 5-6%. I prefaced my post by saying that I was only talking about beers that exceed 8%. I've hit over 14% on some of my beers by adapting mead techniques. I stand by my post. Like I said, I have empirical data to back it up over the last 14 years.

So, are you a sheep? Or do you wanna be a shepard? Your choice.

:cheers:
Wade

 

[KCWortHog]

wildaho I have been brewing since 2003. And I think you misunderstood my post.

The Bruery *is* oxidizing their beer - but they are doing it on purpose because it contributes a desirable character to their product. I thought that Oskaar was saying that introducing oxygen to the beer throughout fermentation won't oxidize high-alcohol beers. Perhaps that's not what he was saying and I misunderstood the intent of his post - clearly that'd be the first time that's ever happened on the internet.

And btw I don't disagree with you about adding O2 to high gravity beers in the first 1/3 of fermentation. i think you misunderstood *my* post as well To summarize:

1. I thought Oskaar was saying that adding O2 to high-gravity beers won't oxidize them
2. I think you thought I was saying no one should ever add oxygen to high-gravity beer

On re-read I suspect neither is correct...

(eta - and FWIW, I use an O2 tank to oxygenate my wort and I do aerate my must both at pitching and 24 hours after pitching with my nutrient addition. now that I know more about the 1/3 sugar break, I"ll rely on that instead of time duration for aeration. Just wanted to make it clear that I'm definitely a proponent of oxygenating must/wort but not of intentionally oxidizing beverages when it's not appropriate for the style! )

 

[Oskaar]

wildaho I have been brewing since 2003. And I think you misunderstood my post.

The Bruery *is* oxidizing their beer - but they are doing it on purpose because it contributes a desirable character to their product. I thought that Oskaar was saying that introducing oxygen to the beer throughout fermentation won't oxidize high-alcohol beers. Perhaps that's not what he was saying and I misunderstood the intent of his post - clearly that'd be the first time that's ever happened on the internet.

The Bruery is oxygenating not oxidizing their beer. Small doses of oxygen through the early stages of fermentation, and in some cases throughout fermentation will not "oxidize" their beer. There are no reductive characters, aromas, flavors or compounds in their beers that arise from the introduction of oxygen, hence no oxidation, and their beers are not oxidized.

Again, I'm talking specifically about increasing the amount of dissolved oxygen in the must or wert, not oxidizing the must or wert which indicates a reductive or off-character that detracts from the overall character of the finished product.

Oxygen is required during the early aerobic fermentation in order for the yeast cells to develop fully and form strong and elastic cell walls. Oxygen should be considered an essential yeast nutrient and slight aeration during yeast stationary and growth phases increases the production of lipids (principally oleanoloic acid) and sterols (ergosterol and zymosterol) which are important cell membrane constituents. This is important for the fermentation when it goes into heavy alcohol production (most of the alcohol is produced in the early 1/3 of the fermentation according to Dr. Clayton Cone of Lallemand) it is also a key in the yeasts ability to withstand the toxic effects of the EtOH level as it rises during fermentation.

And btw I don't disagree with you about adding O2 to high gravity beers in the first 1/3 of fermentation. i think you misunderstood *my* post as well To summarize:

1. I thought Oskaar was saying that adding O2 to high-gravity beers won't oxidize them

What I'm saying is that oxygenating/micro-oxygenation of beers during the logarithmic growth curve of yeast will not "oxidize" beer, mead or wine. There are also instances where oxygenation is used throughout the entire fermentation process to the benefit, not oxidation of whatever is being oxygenated.

2. I think you thought I was saying no one should ever add oxygen to high-gravity beer

On re-read I suspect neither is correct...

(eta - and FWIW, I use an O2 tank to oxygenate my wort and I do aerate my must both at pitching and 24 hours after pitching with my nutrient addition. now that I know more about the 1/3 sugar break, I"ll rely on that instead of time duration for aeration. Just wanted to make it clear that I'm definitely a proponent of oxygenating must/wort but not of intentionally oxidizing beverages when it's not appropriate for the style! )

Sounds like we're pretty much on the same page. I don't use one rule for everything that I make. Some stuff I oxygenate only early on, other stuff I will leave open (but covered with a cloth to keep out chunky stuff) through out most of the fermenation but cover with an airlock at the first racking.

Also, if you leave an airlock off mead, beer and wine will all oxidize, mead not as quickly as beer or wine, but it will go to oxidation just as the other two will without an airlock. You can prove this to yourself with a small test batch as Medsen suggested. I'll go a step further and say instead of an airlock, just cover it with a cloth and secure it in place so you don't have critters swimming around in the mix.


Hope that helps,

Oskaar