This is part of a series called Wine Words, a glossary in the works that breaks down the barrier between those in the wine know and those who have no idea what the hell everyone's talking about. A new word posts once a week, and can cover anything and everything from a grape name or region, to a winemaking or tasting term. If you have a recommendation or request, please leave it in the comments.
Malolactic Fermentation (n.) Wine Making Term
The Oxford Companion to Wine calls this process Malolactic Conversion, since no alcohol is actually produced as a result of the chemical reaction. That makes complete sense, though I've never encountered it as such except in the Companion. It's also referred to as Malo, ML and MLF, which reminds me of MILF and scrambles my focus immediately when I see it. It is sometimes considered a secondary fermentation, not to be confused with a second fermentation, which is actually a re-fermentation and technically a flaw.
The malolactic conversion/fermentation converts the harsh malolactic acids in a wine (think Granny Smith apples) to softer lactic acid (think milk), which gives the wine a softer texture. Almost all red wines go through malo and many whites. Sometimes you'll hear, "There was no malo on this white wine," which pretty much insures it's going to be high-toned and crisp, and was a deliberate move on the part of the winemaker. Left to its own devices, a wine will undergo malo every time. While yeasts are responsible for the alcoholic fermentation, turning sugar into ethanol as they party through the grape juice, a malolactic fermentation is the result of naturally occurring bacteria feeding on the malic acids in the finished wine. As with alcoholic fermentation, carbon dioxide is a byproduct of the malolactic conversion, so when it happens in bottle (by accident), it'l leave a little prickle behind.
Another byproduct of this process is the production of the organic compound diacetyl, which has a buttery flavor and is in fact naturally occurring in butter. This is where that butter bit in California chardonnay comes from. Yesterday I was shopping for popcorn at the market and noticed in the ingredient list for the Butter Flavor option, diacetyl. That form of diacetyl is manufactured and a wee bit controversial. Don't confuse the two.
Now if you're a "chardonnay hater" there's a good chance the only chardonnay you've had - that you know about - was one that went through heavy malo. That thick, buttery style is an acquired taste, even if you do like your toast buttered. But wines can experience partial malo and the diacetyl production managed. Next time your wine pusher says, "This white has some malo," you'll have a better idea of what she's talking about, but don't assume butter bomb. There are a great many degrees between subtlety and excess.