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(Don S) wrote in message . com>...
> >
> > IMHO, this is really a misconception fostered by a lot of winemaking
> > and brewing books. There really aren't two separate phases of the
> > fermentation as some state. A lot of books refer to a lag or growth
> > phase and then an alcohol production phase. In reality, yeast will
> > start producing alcohol and CO2 almost immediately, unless the sugar
> > content of the must is very low and there is O2 present. They will
> > divert some energy towards building cell mass and budding, but that
> > doesn't mean they forego fermentation.
> >
>
> Everything I have read in books and read posted here indicates
> that there are two phases. The first is a reproductive phase where
> the yeast is reproducing more than it is producing alcohol. That
> phase is an aerobic phase where oxygen is required. The second
> phase is anerobic and is the alcohol producing phase.
>
> Don

I did say misconception, didn't I ?

It is well documented by UC Davis and some yeast companies that if the
must/wort has significant sugar (like typical musts/worts), there is
no aerobic respiration by the yeast. They will use O2 to keep the cell
walls healthy, but they will immediately start fermenting, which
doesn't use O2.

Andy