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Re: Yeast fermentation

George wrote:

> Yeast ferments sugars in the ABSENCE of air -- therefore, in wine
> fermentation, one uses an "air-lock".

True enough, but it also metabolizes sugars in the presence of air.  The reason
you need to keep air out when you are making wine is that you want alcohol.  If
it is the CO2 that you want, you can get more of it by letting the yeast have some
oxygen, so that the sugar can be fully metabolized to CO2 and H2O.

David Ozenne
Fremont, CA