It may also interest you to know that napa valley vintners state that they kill off the natural yeast by adding their own yeasts to make wine... as do most winemaking companies.

They affirm that the grape juices, if left to ferment on their own, will turn to vinegar in a days time. Man must intervene in the winemaking process.

Even homemade wines require man to add ingredients and to monitor the sugar and yeast levels.

Natural fermentation is not that which produces the alcohol so many put to others lips, but rather vinegar.