View Full Version : Aeration vs Degassing

01-23-2015, 02:49 PM
I'm confused:
"Aerate throughout initial fermentation by stirring violently."
"Degas throughout initial fermentation by gently stirring, but not violently like aeration."
How can I do both?
What am I missing here?
I had set up to degas with a vacuum pump, but if I turn around and aerate, am I un-doing what I have done in degassing?

My theory: CO2 builds up in the batch and degassing pulls it out. Then, when I aerate, it forces Oxygen, not co2, back into the must. Am I on the right track?

Can someone present a "formula" for these two processes? Maybe like "Aerate every day and degas only every other day." or whatever someone has found to work.
When do I stop either or both of these?

Is a final de-gassing just prior to bottling a good practice?

Any help would be appreciated.


Medsen Fey
01-23-2015, 03:20 PM
Aeration is to get oxygen into the must for the yeast to develop fully. This needs to be done at the very beginning of fermentation, at least a couple of times, and folks will continue to aerate up to the 1/3 fermentation point. After that, you really don't want to get oxygen into your mead as a general rule. As your aerate, whether that be with a whisk, a power stirrer with a drill, a splash racking or any other method, there will be some release of CO2 (degassing) which can be enough to cause an MEA if you aren't careful.

After you've passed the 1/3 fermentation point, the goal of degassing is to lower the CO2 is solution without introducing too much (or any oxygen). If you are using a power stirrer, you want to agitate gently. I will sometime swirl the mead without removing the airlock. A vacuum aparatus degasses things very nicely. Some folks have great success using a large stir plate while keeping it under airlock. The key here is that degassing is probably of minimal benefit. Moving the yeast to get them back up into the suspension probably provides most of the benefit and any release of CO2 is probably incidental. You will find that opinion varies on this, and some sites have folks that insist you have to degas you mead, but frankly there really isn't much in the way of evidence to support this assertion. I swirl to keep yeast suspended because there is good evidence for that, and after fermentation is complete I do some aging at room temp, and I can assure you that my meads all become quite still without ever having to fuss with degassing. I prefer to spend my effort doing something that makes a difference in the outcomes of my meads like careful sulfiting and sanitation. YMMV.