Before revision: Yeast (Saccharomyces cerevisiae), nutrients, and oxygen are added, starting an alcoholic fermentation which converts the sugars in the juice to ethanol, producing apple cider.
After revision: Autochthonous or inoculated yeasts, mainly Saccharomyces cerevisiae, start the process of alcoholic fermentation which converts the sugars in the juice to ethanol, producing apple cider.