Malolactic fermentation, also referred to as secondary fermentation, uses bacteria to transform muscular malic acids (think green apple) into smoother tasting lactic acids (think milk). The process reduces the wine’s acid content and helps create a creamier textural quality in the mouth. With the exception of very light styles, like Beaujolais Nouveau or Dolcetto, all red wines undergo malolactic fermentation.

Secondary conversion for white wines depends on the region, varietal and style the winemaker wants to create. Lighter grapes, like Riesling, which feature crisp acidity and explosive aromatics, usually avoid malolactic fermentation so that the grape's natural vibrancy isn't lost. However, depending on the desired wine style, larger bodied varietals, like Chardonnay and Viognier, may go though at least some degree of secondary fermentation to add complexity and smoother textural qualities.