Malolactic Fermentation (“Malo”)

A sip of wine can transport you lots of places. Sangiovese can send you to a dirt road in the Tuscan hills, while assyrtiko can make your living room blinds seem like flowing white curtains on Santorini. Why, of all places, does chardonnay bring to mind the concession stand at a movie theater?

The answer is a process called malolactic fermentation, or ‘malo’ for short.

In order for grape juice to turn into wine, yeasts metabolize sugar to create alcohol. After that’s complete, ‘malo’ gets underway. This ‘secondary fermentation’ involves tart malic acid (found in green apples) being converted into softer lactic acid (found in milk). The result is rounder, creamier wines, which develop buttery flavors due to a malo byproduct called diacetyl. As it happens, diacetyl is the very same compound that’s added to microwave popcorn to provide its signature “AMC concession line” aroma.

While pretty much all red wines undergo malo, its usage is much more variable for white wines. Chardonnay producers often encourage it because chardonnay on its own has relatively neutral flavors and aromas, so ‘malo’ is one of the tools they can use to shape the wine to their liking. If their chardonnay is low-acid to begin with, and they double down on this softness with malo and extensive oak treatment, then they can get “butter bombs,” like you’ll find from parts of California. But when used as part of a balanced approach, ‘malo’ can add stability and complexity to chardonnay, and help create some of the world’s best wines, like in Burgundy.

More aromatic varietals, like sauvignon blanc and riesling, rarely see any malo because high-acidity and pure varietal expression are desirable. You know, so you can keep taking trips to Santorini between afternoon conference calls.