Hello,
I am also Italian and most of my relatives still do NOT add any yeast to
their crushed grapes. There will always be wild yeast present in all fruits.
The crushed grapes always start fermenting on their own. The wine will be
noticeably better with the addition of store bought yeast. I assume that the
wild yeast will still grow and reproduce along with the cultured yeast. You
may want to add campden tablets to the crushed grapes to kill off any wild
yeast spores present before adding cultured yeast just to be sure.
Most wine made by leaving the crushed grapes alone produce good results.
However, most of the problems arise from improper cleanliness and oxidation,
turning a good wine bad rather quickly. The old school vintners are hard to
change in their methods :-) My father used to use an old oak barrel to
ferment his grapes in. The old (15 years++) wood harbored many a bacteria
and usually produced bad wine. It took years of convincing to switch to a
plastic fermented that was sterilized!!

Al
"Richard Sydney" > wrote in message
om...
> My father of italian origin has been making perfect wine for years and
> has not once used yeast. What is the purpose of adding yeast? What
> does it do?
>
> Richard Sulfaro