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I'm wondering if degassing and removing the suspended CO2 (a part of, and a percentage of the wine) changes the totals for ABV% as it applies to yeast tolerance. It seems that by degassing you would inherently increase the existing ABV% because there is less total parts then when you started off before degassing. Even if 1% of the mead/wine is CO2, and it's released through degassing, that would mean the ABV would increase.

On the flip side, by removing one of the two toxins(ethel alcohol & CO2)from the yeast, does this give them more room and less stress to ferment further? Since CO2 is toxic to yeast, does it inhibit the yeast's ability to fully ferment the larger amount of sugars in wine/mead?

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I have tested this personally and have not been able to record any perceivable differences in SG readings. Sometimes degassing will invigorate a slow ferment but nothing more than a good stir would. I do see your math behind the ABV increase and I still believe that to be true as well.

Degassing is something you should be doing throughout primary and into secondary. CO2 can be toxic to yeast, stressing them out, and potentially producing some off flavors and aromas. Keep in mind, degassing is different than aeration; you're just trying to get the dissolved CO2 out of solution, not to whip the crap out of it. Basically, do it a few times during primary, before each SNA addition. Adding nutrients and then degassing is a sure way to end up with partially fermented honey all over your floor. I repeat: Degas and THEN add nutrients. I then tone it down a bit for the secondary until fermentation is over and CO2 stops being released from the process.

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ABV is Alcohol By Volume. Carbonation does not change the volume. So it would not effect the ABV.

c02 is dissolved into the liquid. Meaning that the c02 molecules fit in between the liquid molecules and do not change the total volume of the liquid. As long as the c02 is trapped the liquid volume is unchanged, once released (bubbles) the gas displaces liquid volume making a larger total volume which can cause issues with volume calculations during this phase of release.

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  • What are you saying? "Carbonation does not change the volume." And in next paragraph you say "...once released (bubbles) the gas displaces liquid volume making a larger total volume..."
    – DV8DUG
    Commented May 18, 2016 at 4:04
  • @DV8DUG the actual volume of the liquid does not change, but in a graduated cylinder there is a false increase in volume from the displacement of the gas bubbles. Same principle of how the liquid level rises when putting in a hydrometer. Its displacement not a volume increase.
    – Evil Zymurgist
    Commented May 18, 2016 at 14:20
  • @ Evil Zymurgist. So you might have said "...once released (bubbles) the gas displacement makes a SMALLER total volume."
    – DV8DUG
    Commented May 19, 2016 at 9:07
  • @DV8DUG No. Released cO2 as in no longer disolved and is now bubbles, at this phase of degassing. This is the stage that gives a false LARGER volume for measuring instruments. Once degassed the volume is the same as the liquid with disolved cO2.
    – Evil Zymurgist
    Commented May 19, 2016 at 20:20

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