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Thread: Aerating

  1. #1

    Default Aerating

    I have read in the NewBee section and it was suggested on the forum that you should aerate the Mead for the first 1/3 of fermentation.

    I put together a batch of Wildflower mead last night and reluctantly aerated the carboy this morning before I came in to work. I am planning to aerate again tonight.

    But I am conflicted because as a homebrewer you are not supposed to introduce oxygen after pitching the yeast but with mead it seems that is not the case.

    Can someone please pacify my concerns about oxidation?

  2. #2

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    Mead and the precursor must is generally more resistant to oxidation than wine/wine must and beer/wort. It's one of the nice little features of honey.

    Aeration and staggered nutrient additions keeps the bulk of the yeast in aerobic/reproduction mode as long as possible. Aerobic-mode yeast metabolizes dramatically more sugar and thus produces dramatically more alcohol than stationary or anaerobic-mode yeast. That all results in a faster fermentation and less stress on the yeast. Less stress on the yeast means it's less likely to produce off flavors.

    In the case of mead, at least until the 1/3rd sugar break, the benefits of aeration vastly outweigh any potential downsides.

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    Well to start with, mead must is not as prone to oxidation as beer wort. I'm not saying that you can't oxidize it - you can - but it doesn't occur as easily. The yeast themselves need the oxygen in order to form healthy cell membranes to grow and divide, and to maintain resistance to alcohol as it increases in concentration. In wine and mead must, lack of oxygen exposure leads to stuck fermentation, and lower amounts of sugar consumption.

    You don't need aeration to make beer in most cases because the yeast come packaged with enough sterols and lipids in their membranes from their production process (which uses plenty of oxygen) to easily ferment up to about 6% ABV. If you try making a high gravity barley wine type beverage, aeration becomes important, and using this technique will improve the outcomes.

    You can read more Here and Here.

    I hope that helps.

    Medsen
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    (Past years are always better)

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    It is also common practice in winemaking to aerate early in the course of fermentation. As Medsen points out, the "rule of thumb" to never introduce O2 to a fermenting wort is really only applicable to beer and other beverages of similar alcohol concentration.
    Na zdrowie!

    Wayne B.

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    Red wine making involves constantly adding O2 to the must as you punch down the cap...

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    Quote Originally Posted by fathand View Post
    I have read in the NewBee section and it was suggested on the forum that you should aerate the Mead for the first 1/3 of fermentation.

    I put together a batch of Wildflower mead last night and reluctantly aerated the carboy this morning before I came in to work. I am planning to aerate again tonight.

    But I am conflicted because as a homebrewer you are not supposed to introduce oxygen after pitching the yeast but with mead it seems that is not the case.

    Can someone please pacify my concerns about oxidation?
    I actually add O2 during my primary in beer making as well. Yeast need O2 to develop fully. During the very active stages of early fermentation in beer the aggressive off-gassing will strip any O2 not being absorbed by the yeast before it can cause oxidation. Tyler King who is the Director of Brewing Operations at The Bruery in Placentia, CA adds O2 to their fermentations early on, and in some cases almost all the way through the ferment.

    Their Black Tuesday, Russian Imperial Stout is currently #3 in the top 100 beers worldwide, and #1 in the top 100 beers in the USA. They also have two more beers in the top 100 both worldwide and in the US.

    See here for a link to the Beer Advocate site for rankings.

    I say do whatever makes you comfortable, but, don't let yourself fall into a rut over "rules" that you have not actively challenged yourself.

    Hope that helps,

    Oskaar
    Is it tasty . . . precious?

  7. #7

    Default

    Number 1: understand that beer and mead have different needs.

    Number 2: understand that the beer world needs to be shaken and stirred on occasion. For any beer over an estimated 8%, I have been following the aeration techniques for mead. Aerate the hell out of them until the 1/3 sugar break. If you do, you'll have better attenuation and cleaner ferments. Your aging times will be much shorter too.

    Number 3: Ignore the mythology and open your mind. Charlie Papazian built a saga 30 years ago and it's been taken as gospel ever since. Us heretics have been playing around since then and have actual empirical data to back up our procedures. A book, or maybe three books, say it won't work. I have data to actually prove that mead techniques work for big beers too. Read everything with a grain of salt (including this). But until you try it, how can you honestly say that it doesn't work?
    Wild In Idaho
    Mead, like life, is a journey and not a destination. So stop and savor the flavors along the way!


    "Gawd, I hate drinking mead and posting in the forums."

    Nothing currently fermenting!

  8. #8

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    Adding oxygen to beer once fermentation begins WILL OXIDIZE your beer. That said, some beers are actually suited for oxidation - like barleywine, imperial stout, or some strong ales. Oxidation during will likely add a sherry component to beer, which is often desired in stronger, higher-gravity beers. But it does NOT belong in most beer and steps to avoid oxidation are warranted.

    In other words, The Bruery intentionally oxidizes their RIS to add to the flavor and depth of the beer. It "works" because they WANT that flavor there. So I'd make sure that the sherry component is actually desired in your beer before you go introducing oxygen to primary. If you're making an Imperial IPA with 8%+ alcohol, you should not be introducing oxygen because the off-flavors caused by oxidation are undesirable in that style. IOW, don't go solely by your ABV but by the flavor profile of the beer. Old Ale? OK. Barleywine? Sure. Imperial Kölsch? Not so much.

    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 )

    phew, I feel better now.

    As for aerating must, I've been looking into this as well. A few people on here have said that simply shaking your carboy will both expel CO2 (which it will) AND aerate the must (which I don't believe). Since CO2 is heavier than air and is trapped in the headspace & neck of the carboy, how could O2 get "sucked down" into the carboy? The simple weight of the CO2 would prevent that from happening (and is precisely why purging kegs with CO2 is an effective way to avoid oxidizing beer when you rack it from carboy to keg).

    So I don't know how a lees stirrer or shaking (or any method other than compressed O2 or an air pump) would work. Anyone know?

    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.

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    Quote Originally Posted by KCWortHog View Post
    As for aerating must, I've been looking into this as well. A few people on here have said that simply shaking your carboy will both expel CO2 (which it will) AND aerate the must (which I don't believe). Since CO2 is heavier than air and is trapped in the headspace & neck of the carboy, how could O2 get "sucked down" into the carboy? The simple weight of the CO2 would prevent that from happening (and is precisely why purging kegs with CO2 is an effective way to avoid oxidizing beer when you rack it from carboy to keg).

    So I don't know how a lees stirrer or shaking (or any method other than compressed O2 or an air pump) would work. Anyone know?
    The CO2 will diffuse out fairly quickly. I usually take off the airlock, give it a swirl or two to expel some dissolved CO2, then let it sit for a minute or so before putting a cap on it and shaking it to aerate. Then I open it again, let the CO2 dissapate, then cap it and aerate it again.

    I use the same technique when using a lees stirrer.

    CO2 is heavier, but it doesn't form a neat layer that will stay for long. Take off that airlock and it'll be gone almost immediately as far as I understand it.

  10. Default

    Take off that airlock and it'll be gone almost immediately as far as I understand it.
    But if CO2 is heavier than air, why would it float upward into the air when the airlock is removed? It doesn't - it stays put. (again, that's why you can purge a keg with CO2 and leave it open at the top while racking and not risk oxidation.) The airlock isn't there to keep O2 out; it's there to prevent contamination from ambient organisms.

    So we know that:
    1. CO2 is heavier than air. Therefore it will always be lower (in position) than ambient air unless O2 is placed underneath it.
    2. There's nothing under the CO2 other than mead

    So how is the O2 getting underneath the CO2 unless it's being placed there by something? CO2 is escaping the carboy because some is being expelled from the mead itself. Therefore, the CO2 being released from the body of the mead is pushing up on the CO2 in the neck/headspace of the carboy and expelling some of the gas. But the movement of gas is upward. And since CO2 is heavier than air, it is not logical that O2 would somehow magically move downward. That's the part I don't understand.

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    Quote Originally Posted by KCWortHog View Post
    When you remove the airlock, the CO2 stays put. It is heavier than the air outside the carboy, so it stays put (again, that's why you can purge a keg with CO2 and leave it open at the top while racking and not risk oxidation.).

    So we know that:
    1. CO2 is heavier than air. Therefore it will always be lower (in position) than ambient air unless O2 is placed underneath it.
    2. There's nothing under the CO2 other than mead

    So how is the O2 getting underneath the CO2 unless it's being placed there by something? CO2 is escaping the carboy because some is being expelled from the mead itself. Therefore, the CO2 being released from the body of the mead is pushing up on the CO2 in the neck/headspace of the carboy and expelling some of the gas. But the movement of gas is upward. And since CO2 is heavier than air, it is not logical that O2 would somehow magically move downward. That's the part I don't understand.

    Someone will be along in a second to explain why it will dissapate quickly I imagine. I don't understand the process well enough to explain it properly to someone else, just well enough to grasp it for myself. It's not magic, I believe it is ozmotic pressure that will cause the heavier CO2 to dissapate, but that could be inaccurate.

    Medsen's explained it a few times, and that CO2 will definitely be gone fast, simply being heavier than O2 is not enough, there are more physics at work than just simple weight!
    Last edited by AToE; 11-13-2009 at 03:34 PM. Reason: clarity

  12. Default

    That's what I'm looking for - and sorry, I edited my post to try to explain better

    I think he posted something about it before, but the thread devolved into general chit-chat before a clear answer was provided. I hope someone can answer this for me as my husband and I have talked about this a few times now and still can't figure out how you're supposed to be able to aerate without a forced oxygen supply.

    ETA - I do remember someone posting some studies about the relative effectiveness of different aeration methods (oskaar?), but I don't recall that they talked about it in the context of mid-fermentation.
    Last edited by KCWortHog; 11-13-2009 at 03:43 PM.

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    If it's not osmotic pressure I'm going to be embarrassed! Whatever the reason, it definitely works!

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    Quote Originally Posted by KCWortHog View Post
    Several people on here have said that simply shaking your carboy will both expel CO2 (which it will) AND aerate the must (which I don't believe). Since CO2 is heavier than air and is trapped in the headspace & neck of the carboy, how is oxygen supposed to get "sucked down"...
    I'm going to leave the beer oxidation discussion for others who brew more than I do.

    Now for the aerating in a carboy, keep in mind that just because CO2 is heavier than air does not mean that the two form into layers by weight like liquids do. Gases behave differently; In a closed space the molecules will bounce around to fill the whole space in a uniform concentration, so the minute any air gets into the carboy headspace, it will begin diffusing through the entire volume.

    Even though CO2 is being produced, since there is a concentration gradient of Oxygen and Nitrogen on the outside of the carboy relative to the inside of the carboy (which essentially has none), the moment you take the airlock off, oxygen and nitrogen start to diffuse in. If you then begin swirling the mead and creating a vortex with a lower pressure in the center it will suck the oxygen containing gas down into the mead and oxygenate it. There is plenty of anecdotal evidence that this works because people are able to successfully brew very high gravity meads in a carboy without using starters - unless the yeast get oxygen (or other sterol supplementation) that isn't going to happen.

    Now if you have a airstone and a pump (or an O2 tank) and want to use it, there's certainly nothing wrong with making use of technology. I personally don't do primary in a carboy - I typically use a bucket, and then I usually don't even seal the lid. I just have it loose on top to keep critters out. When I aerate, take off the lid and use the low tech approach with a whisk. About 30 seconds of that, and my yeast get plenty of O2. Some people just keep open fermenters (usually covered with a cloth to keep stuff from dropping in)

    Just about any approach to give the yeast some oxygen works and which one you use is much less important than the fact that you use one. I'd love to see someone with an O2 meter measure the saturation of must with these different approaches to document it.

    Medsen

    Sorry AToE it's not osmotic; that refers to fluid shifts through a membrane due to concentration of solids. Nice try though!
    Last edited by Medsen Fey; 11-13-2009 at 04:01 PM.
    Lanne pase toujou pi bon
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    Quote Originally Posted by KCWortHog View Post
    But if CO2 is heavier than air, why would it float upward into the air when the airlock is removed? It doesn't - it stays put. (again, that's why you can purge a keg with CO2 and leave it open at the top while racking and not risk oxidation.) The airlock isn't there to keep O2 out; it's there to prevent contamination from ambient organisms.
    When racking if you flushed with CO2, it will give you a few minutes in which to rack before oxygen makes its way in the container. However, once you are done, you need to flush the air out of the headspace again because oxygen will be in that space if it was open to air during racking. This is why I sometimes rack from keg to keg without it being opened to air (that and because it is easier - I'm all about easier.)

    The airlock is in fact there to keep air out. This is why you can store something under airlock for months or years without it oxidizing. If you store a mead in a container without an airlock you'll wind up with vinegar (if you're lucky) or just spoiled mead.
    Lanne pase toujou pi bon
    (Past years are always better)

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    Quote Originally Posted by Medsen Fey View Post

    Sorry AToE it's not osmotic; that refers to fluid shifts through a membrane due to concentration of solids. Nice try though!
    Darnit!!!

  17. Default

    Quote Originally Posted by Medsen Fey View Post
    When racking if you flushed with CO2, it will give you a few minutes in which to rack before oxygen makes its way in the container. However, once you are done, you need to flush the air out of the headspace again because oxygen will be in that space if it was open to air during racking. This is why I sometimes rack from keg to keg without it being opened to air (that and because it is easier - I'm all about easier.)

    The airlock is in fact there to keep air out. This is why you can store something under airlock for months or years without it oxidizing. If you store a mead in a container without an airlock you'll wind up with vinegar (if you're lucky) or just spoiled mead.
    Right. But the airlock is there to prevent ambient bacteria & yeast from getting in - not to prevent oxidation.

  18. Default

    Quote Originally Posted by Medsen Fey View Post
    If you then begin swirling the mead and creating a vortex with a lower pressure in the center it will suck the oxygen containing gas down into the mead and oxygenate it. There is plenty of anecdotal evidence that this works because people are able to successfully brew very high gravity meads in a carboy without using starters - unless the yeast get oxygen (or other sterol supplementation) that isn't going to happen.
    And they're not using O2 tanks or air pumps?

    I typically use a bucket, and then I usually don't even seal the lid. I just have it loose on top to keep critters out. When I aerate, take off the lid and use the low tech approach with a whisk.
    Seems like that approach would introduce a lot more O2 than swirling a carboy because of the much wider exposure to air and the action of the whisk pulling air downward. Clearly I'm still struggling to see how to aerate a carboy without some sort of tool (and a lees stirrer still doesn't click for me - seems the 'vortex' wouldn't be strong enough - but I am fully willing to admit naiveté here).

    I'd love to see someone with an O2 meter measure the saturation of must with these different approaches to document it.
    Same! As well as some way to look at CO2 vs. O2 (if only we could color them!) and watch the patterns of movement by swirling a carboy around. I just don't imagine that rocking a carboy would sufficiently aerate... I need visuals! Diagrams! video!

    Quote Originally Posted by Medsen Fey View Post
    When racking if you flushed with CO2, it will give you a few minutes in which to rack before oxygen makes its way in the container. However, once you are done, you need to flush the air out of the headspace again because oxygen will be in that space if it was open to air during racking.
    Hmm, that's true. And I was thinking earlier too that if you open up a bottle of beer then re-cap it an hour later, even without moving it, you've introduced oxygen. I give up.

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    Quote Originally Posted by KCWortHog View Post
    Right. But the airlock is there to prevent ambient bacteria & yeast from getting in - not to prevent oxidation.
    If you want to try if for yourself, make a nice fruit melomel of your choice, but make it a small batch; say a gallon. Then rack into a secondary container without topping it up so you have some headspace. You can flush it with CO2 if you like. Then put an airlock on it, but don't put any water in it, just keep the cap on. That will keep the critters out, but let air in. Then put it away and let it age for 6-12 months, and then try it.

    If you don't like sherry, you won't like it.
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    Quote Originally Posted by KCWortHog View Post
    Seems like that approach would introduce a lot more O2 than swirling a carboy because of the much wider exposure to air and the action of the whisk pulling air downward. Clearly I'm still struggling to see how to aerate a carboy without some sort of tool (and a lees stirrer still doesn't click for me - seems the 'vortex' wouldn't be strong enough - but I am fully willing to admit naiveté here).
    I don't think most people just swirl, they also slosh it so that it splashes. Swirling pulls O2 down (or just leaving it open for a bit lets O2 in) then splashing actually mixes it in. I shake the heck out of 1 gal batches.

    And for the lees stirrer, also used in a way to not just cause swirling and mixing. If you put the stirring end of the lees stirrer an inch or two below the surface and then pull the trigger you'll get intense splashing, that's what'll do the actual thorough aeration.

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