What does Fermentation mean?

Fermentation is the process in which yeast turns grape sugar into alcohol and carbon dioxide; the field often shows the vessel and yeast used.

Also known as: Alcoholic fermentation, Primary fermentation

Fermentation is the process in which yeast converts the sugar in grape must into alcohol and carbon dioxide. It is the step that turns grape juice into wine. On the wine page the field often describes the vessel used and whether the producer used cultured yeast or spontaneous fermentation.

Fermentation can take place in stainless steel tanks, oak barrels, concrete tanks or amphorae. The vessel affects temperature control, oxygen contact and texture. Temperature matters a great deal: whites are often fermented cool to keep fruity aromas, reds warmer to draw colour and tannin from the skins. Red and orange wines ferment with the skins, most whites and rosés on the juice alone.

Fermentation usually lasts from one to a few weeks. If it is stopped early, sugar remains. After alcoholic fermentation many wines also go through malolactic conversion, in which bacteria turn sharp malic acid into softer lactic acid. It is common in red wines and gives whites such as chardonnay a rounder, sometimes buttery note.

Details about fermentation help you understand the wine's style, from clean and fruity to textured and complex.