From Vine to wine
Primary (alcoholic) fermentation is the starting point for each individual style of wine.
The actual winemaking approach depends on the winemaker, who is looking to produce a wine with a particular style, quality and aging potential.
The primary, or alcoholic, fermentation of Champagne wines is the process that transforms the grape musts into wine: the yeast consumes the natural grape sugars, producing alcohol and carbon dioxide (CO2) along with other by-products that contribute to the sensory characteristics of the wine.
Primary fermentation takes place immediately after pressing, usually in stainless steel tanks though some producers still ferment their wines in wood.
Malolactic fermentation (MLF) is the process that transforms malic acid into lactic acid. Like all forms of fermentation, MLF influences wine aroma development, in this case making for softer, riper, generally creamier sensations.
MLF is an optional process, used by all but a few Champagne makers who avoid it for the sake of crisp varietal expression.