Don’t worry, malolactic fermentation—a process plenty of wines go through after primary fermentation—will not turn your wine into milk. It also won’t actually ferment your wine a second time. It will, however, reduce the overall acidity and create an impression of smoothness, even butteriness. How? Glad you asked!
(Walks into laboratory…)
Just like yeast, malic acid occurs naturally in wine grapes. In a finished wine, the presence of that malic acid can be more or less desirable (malic acid has a tart taste, often compared to the flavor of unripe green apple). If a winemaker so chooses, he or she can convert this malic acid into smoother lactic acid using special bacteria—Oenococcus oeni for those of you taking notes. Sure, it seems weird to dump bacteria into a vat of wine, but then again, we get wine in the first place by encouraging a bunch of single celled organisms to digest grape juice. And we get honey from bee barf. It’s all pretty freaky, if you think about it.
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(Stares off into the distance…)
Back to “malo,” or MLF. It’s a fairly important, and widely used, process in winemaking, though whether a winemaker uses it depends entirely on their goals for the finished product. The result of MLF can be a reduction in acidity from .1 to .3%, which seems low but is perceptible to the palate. It also has the overall impact of “softening” a wine, giving it more roundness and (ideally) better fruit and oak integration (where oak is a factor). Wines light crisp Riesling or light-bodied, fruity reds aren’t appropriate candidates for MLF, since it would detract from a characteristic acidity and you’d lose too much fruit aroma to keep that light-bodied red interesting. But certain white wines—if buttery Chardonnay is your bag—and plenty of medium to heavier-bodied reds are prime candidates for MLF.
As for what you need to know about MLF—essentially nothing, you can enjoy your wine without knowing a thing about it. But if you want to know what goes into making that wine taste so particularly smooth and integrated, well, now you know. However, you do not have to mention it at parties or your local wine bar to sound cool. Mention how you once saw Beyoncé—you’re pretty sure—walking out of a Jamba Juice. Much, much cooler.