Malolactic Fermentation – Briefly

Malolactic fermentation is the conversion by bacteria of malic acid into CO2 and lactic acid.  One gram of malic acid converts roughly into 0.67 grams of lactic acid and 0.33 grams of CO2.

What effect does it have on wine?

  1. The primary reason for using malolactic fermentation is to reduce acid in red wines and some selected white wines by organic rather than chemical means.
  2. Maolactic fermentation takes place in all red wines.  In white wine production, it is a winemaker’s decision to go through full, partial, or no malo at all, depending on the style of wine he or she desires to create.
  3. Malic acid has a harder edge than the softer lactic acid.  Therefore, a wine high in malic acid is naturally more acidic; therefore, the greater the percentage of malolactic fermentation, the less acid will be perceived on the palette, thus the smoother the wine.
  4. A young wine loses its hard and acidic edge:- its color loses some of its vividness, – the grape odor becomes richer and more vinous. Wines become more mellow and will be perceived as more full-bodied.  Also,  wines tend to become buttery as a result of the formation of diacetyl during the malolactic fermentation.