Following the harvest, the cellar master supervises the entire wine-making process. Harvested grapes are pressed, and the juice, or must, is stored in barrels (or stainless steel tanks, in the large cooperatives) to ferment. A natural process, fermentation occurs after the sugar in the must comes into contact with yeast on the grapes” skin. This causes the sugar to convert to alcohol. The high sugar content found in the ripest grapes thus produces the strongest wine (a 15 percent alcohol content is about the maximum possible). Sometimes, if harvest are not fully ripened because of poor weather conditions, sugar may be added. When sugar content is low, barley might be added, to give the wine “body” and reduce sourness without diminishing the alcohol.
After fermentation the wine is moved to new, clean containers and left to age. Sediments settle to the bottom of the barrels, and the wine is again drawn off, or racked, and moved to another clean barrel. Racking may be repeated several times as the wine matures. Finally, in a process known as fining, an additive draws out all remaining sediments and the wine is filtered. Crystal clear, the wine is now extremely dry. This means that almost all of the natural sugar has been converted to alcohol.