You will hear or read the term ML or Malolactic Fermentation thrown around a lot in the world of wine-speak. In the overall scheme of things, it is probably not that important for you to understand. However, if you are anything like me, you like to have some idea of what people are talking about. You may also want to know why you like certain wines over others…ML may have something to do with that.
Chardonnay is probably the classic example of what ML is capable of doing. When you pour a glass of chard, do you like it creamy and buttery or on the austere side with some bracing acidity? Malolactic fermentation has a everything to do with that. ML is simply a bacteria that turns malic acid (think Granny Smith apples) into the much softer lactic acid (think a glass of milk). Malic acid is tart and austere whereas lactic acid is soft and approachable.
Malolactic fermentation is a secondary fermentation that occurs after the primary fermentation. Have you ever visited a winery during harvest and noted totes full of grapes just sitting out in the warehouse? These are the grapes going through the initial fermentation. Some wine makers put the must or fermenting grapes into large steel fermenters to go through this primary ferment. What is happening during the primary fermentation is that the yeast is eating up the sugars in the fruit turning it into alcohol. To encourage this, the wine maker will punch the cap of the fermenting grapes down into the juice (sort of like stirring the pot). As this process goes along, the grape juice goes from sweet to dry. Red wines are kept on the skins for color, and white grapes are pressed immediately and the juice is put into tank where it goes through the fermentation process.
After this primary fermentation, the wine maker decides what style he or she would like their wines to attain. ML both in whites and reds causes the wine to become softer and fuller in style (some think more complex). Stopping the Ml process makes for wines that are brighter, more acidic and edgy. ML occurs naturally in juice that is kept on the warmer side, higher PH levels and lower SO2. It can be stopped by keeping the juice colder, lower PH levels and lower SO2. I’m trying to keep this as simple as possible, so suffice it to say, there is a little more that goes on than I just explained. However, these are the basics and should help you have somewhat of a grasp of the term malolactic fermentation, ML or MLF.
So when you enjoy a glass of creamy chardonnay, or a full-bodied softer style red wine, you now know that it went through malolactic fermentation to attain that style.
Stan The Wine Man