What is Malolactic Fermentation?

Malolactic fermentation, usually referred to as "Malo" or "MLF" is a natural phenomenon. It is the transformation of the malic acid present in the grapes and in the wine into lactic acid by lactic acid bacteria, Oenococcus oeni. 

The equation of the MLF is written as follow: COOH-CHOH-CH2-COOH ⇒ COOH-CHOH-CH3 + CO2

Malolactic Fermentation in the wines

The Malolactic Fermentation has a strong impact on the taste of wines. Malic Acid is the acid found in green apples for instance. It is perceived as Bitter, Sharp, Acrid, even Metallic. On the other hand, Lactic Acid brings roundness and softness to the wines and brings notes of Sour Cream, Yogurt. 

As a consequence, wines with a high natural acidity (cool climate, Northern France) do the MLF, while in low acidity wines, produced in warmer climates, the MLF is blocked by the addition of sulfites. 

Malolactic Fermentation:  a recent discovery

Until the XIXth century, nothing was known from this natural phenomenon. The invention of the microscope allowed scientific to observe bacteria and to understand the process. Modern œnology now understands how to start and control the MLF.   

Follow this link for more detailed information.