Step 3
of 6
Fermentation
Yeast eats sugar, makes alcohol. That single chemical reaction is the entire reason wine exists. Yeast consumes the sugar in grape juice and exhales alcohol and CO2.
The winemaker's choices here decide everything: wild yeast or cultivated, cool or warm, stainless steel, concrete or oak. For reds, a daily ritual of “punching down” the floating cap of skins keeps the color and flavor extracting.
When the yeast eats all the sugar, fermentation stops on its own — that's a dry wine. Sweet wines stop early, leaving sugar behind.
