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Old 10-26-2010, 11:22 AM   #11
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If it were me I would go ahead and add nutrient according to the staggered schedule since fermentation has started. However, a more experienced meadmaker may contradict me if I'm wrong!

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Old 10-26-2010, 02:19 PM   #12
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And be sure to aerate it to promote yeast growth at least once or twice.

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Old 10-26-2010, 04:49 PM   #13
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Ok thanks everyone! Aerating and adding the nutrients according to schedule.

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Old 10-27-2010, 08:13 AM   #14
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Is "aerating" effectively just giving the must a shakety shake with the purpose of giving our yeasty friends something to breathe?

If so, why are we also encouraged to degas [does anyone else always read that as "daygar" - ala artiste!?]? Is the aerating (shaking?) done only after adding the yeast and/or nutrient and degassing (attacking with spinny thing?) done daily during the primary?

Total brewbie as you can probably tell so I might well be using some terms incorrectly. Is there a glossary somewhere on this sprawling forum for beginners? I've been reading the mead section for a while and it's starting to sink in but I'm still a bit hazy on some definitions.

Sorry for the hijack - I'm a bit of a thread cuckoo.

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Old 10-27-2010, 01:44 PM   #15
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Every time I see the word "degas" I think "ballerinas".

Aerating is the process of introducing air into the must. It is necessary so that yeast get exposure to oxygen which causes increased sterol production in the cell membrane and allows for increased yeast growth and membranes that are more resistant to alcohol. The are many ways to aerate. Some folks keep the fermentation open without an airlock of lid. In other cases, people open the container and stir or swirl the mead, or they may use a de-gassing wand attached to a drill. I favor a whisk. Some people use airstones and a small pump, while a few will actually use oxygen through an airstone. Opening and shaking will work, but Mead Eruption Accidents (MEAs) are possible.

Whatever the method, if you don't aerate, you run the risk of incomplete fermentations will less total sugar fermented, and less alcohol produced. The bigger question is how much do you need to aerate. There have been no studies with meads that I am aware of, and many will recommend aeration at least once daily during the first 1/3 of fermentation. That is probably more than is required.

In studies of wine, yeast need about 10 mg/L of oxygen to achieve maximal fermentation. A complete saturation of the must with air provides about 8 mg/L of oxygen. So 1 or 2 good aerations after the start of fermentation (ideally at about 48 hours) should be enough to allow the yeast to achieve complete fermentation. Does aerating more cause harm? It hasn't been studied, but experience suggests that it doesn't seem to damage the final product as many award winning meads have been well aerated (and even open fermented).

I hope that helps.

Medsen

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Old 10-27-2010, 01:51 PM   #16
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So "aerating" and "degassing" are the same process? That makes more sense now (though the terminology implies one is putting air in and one is taking it out!).

Future attempts at meadification will involve aerating. Cheers.

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Old 10-27-2010, 02:50 PM   #17
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Quote:
Originally Posted by RedCabbage View Post
So "aerating" and "degassing" are the same process?
No. Aerating is the mixing in of air. Degassing is the process of getting dissolved CO2 out of solution so the mead won't be fizzy. However when you stir, swirl or shake, to aerate, some degassing will occur, and it can be be vigorous enough to cause the MEAs.

Nevertheless, degassing is mostly about getting rid of the dissolved CO2 after fermentation is finished. At that point, you don't want to mix air in, so you may use a different approach that minimizes air exposure. In my case, I will usually swirl the mead while keeping it under airlock, and letting it sit at room temp for some weeks. Like a bottle of soda pop that you leave open on the counter, it doesn't take all that long for it to become flat. Now other folks may use different ways of doing it including, using a vacuum pump, or a degassing whip attached to a drill. I don't like the drill approach because that entails opening the mead and allowing air to mixed in while you are stirring to release the CO2 (effectively the same thing you do with aeration), but many folks do this without problems.

There are some who encourage vigorous degassing during fermentation with the thought that CO2 is toxic to yeast, and degassing allows the fermentation to proceed more rapidly. Since the CO2 is only at one atmosphere of pressure, and you have to get above 7 atmosphere of pressure to significantly impede the yeast, I don't think this is true and I would ask anyone that has any data demonstrating active degassing having a beneficial effect on fermentation to please share it with us.

There is data that swirling the yeast to keep them up in suspension, or having particulate matter that functions in the same way will both allow fermentations to finish a little faster. I typically keep the fermentation under airlock and swirl it a couple of time each day to keep the yeast stirred up. That produces some degassing, which is okay. Truthfully, I haven't seen that swirling makes much difference as the fermentations generally finish about as quick either way.

So I generally don't spend time worrying about degassing. It will happen as my meads sit at room temp for a spell and get racked a couple of times. After that, they are nice and still with minimal effort. However, if you want to get something clear and bottled faster, active degassing after fermentation will speed you along, especially if you are keeping them in a cool storage area.

Medsen
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Old 10-27-2010, 03:36 PM   #18
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Oh, I see. I was confused by your reference to using a degassing wand to aerate. And the physical process for both seems to often be to agitate the brew. It seems quite strange that one might want to both increase the amount of air and decrease it during primary fermentation, but, from what you are saying, a perfectly acceptable method is to whisk the must after day 1 (while your bucket is open for the second stage nutrient, maybe) then do it again after day 2, then leave the primary to finish up (stirring every couple of days if I like to lift some yeast off the bottom), rack to an airlocked demijon and leave it at room temperature swilling it every few days until it clears (maybe racking again if the gunk gets too deep) before bottling.

Sorry for labouring the subject, I guess I'm trying to settle a process into my brain. I've skimmed through a whole load of meadmaking methods across the internet and not many of them have mentioned aerating or degassing. I suppose they are trying to keep them simple.

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Old 10-27-2010, 03:46 PM   #19
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Quote:
Originally Posted by RedCabbage View Post
rack to an airlocked demijon and leave it at room temperature swilling it every few days until it clears (maybe racking again if the gunk gets too deep) before bottling.
I'd change that to read "swirling every few days until it stops releasing CO2 bubbles. Then let it sit (maybe in a cold place) until clear, racking every few months until it stops dropping lees."

But yeah, that process will work (along with many other variations).
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Old 10-27-2010, 05:15 PM   #20
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So, coming from a beer background, aerating during fermentation is BAD. It causes oxidation. So mead is different in that respect? Oxidation ok during fermentation?

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