After finishing the primary fermentation of reds, most wineries will inoculate them with bacteria that converts the malic acid to lactic acid.  This process commences after the yeast has converted the glucose to alcohol; otherwise, the bacteria can consume the glucose and produce acetic acid (vinegar). 

Many winemakers bottle their reds without filtering or by loose filtering whereby bacteria, if present, can reach the bottle.  If malic acid remains, the bacteria can digest it and produce a small amount of carbon dioxide.  A spritzy, red wine is not desirable!  Other reasons for malolactic fermentation include lowering the acidity of the wine and creating a softer texture and complexity from flavors emanating from the process.

In the enzymatic analyses that I conduct for other wineries, I advise that malolactic fermentation is completed when the malic acid level reaches 0.01 grams per 100 mL.