Fermentation

Fermentation meaning in winemaking

Fermentation is the fundamental biochemical process that transforms grape juice into wine through two distinct types of conversion. Alcoholic fermentation occurs when yeasts, primarily Saccharomyces cerevisiae, consume the natural sugars (glucose and fructose) present in grape juice, converting them into ethyl alcohol and carbon dioxide. This process typically takes 7-21 days depending on temperature, yeast strain, and sugar concentration, with most table wines achieving 11-15% alcohol by volume. Malolactic fermentation is a secondary process where lactic acid bacteria, particularly Oenococcus oeni, convert sharp malic acid into softer lactic acid, reducing overall acidity and creating a smoother, more complex flavor profile. This bacterial conversion often occurs naturally or can be induced by winemakers, particularly for red wines and some full-bodied whites like Chardonnay. Temperature control is crucial during both processes—alcoholic fermentation typically occurs at 60-85°F (15-29°C), while malolactic fermentation requires warmer conditions around 68-72°F (20-22°C). The fermentation process also produces numerous secondary compounds including esters, aldehydes, and phenolic compounds that contribute significantly to a wine’s aroma, flavor complexity, and aging potential. Modern winemaking employs various fermentation vessels from stainless steel tanks to oak barrels, each imparting different characteristics to the final wine.

See how wine is made for fermentation’s place in the full process and the choices that change by wine style.