T hose who were drinking white wines in the late 1980s and early ’90s will remember the virtual tsunami of heavily oaked “butter bomb” style Chardonnays that swept the world. Living in London at the time, I couldn’t tell whether sea levels were rising or the entire country was sinking under the weight of the millions of imported cases of Lindemans Bin 65 Chardonnay. A particularly popular example of that style of winemaking, this Chardonnay undergoes a so-called “secondary fermentation” that creates the strong flavor of butter.
As this butter-bomb trend reached what many considered were extreme levels of self-parody, a backlash developed, with some people going so far as to claim that henceforth they were only going to drink “ABC” (Anything But Chardonnay). Others reserved their scorn “ML” (malolactic fermentation), the secondary fermentation technique that the butter-bomb houses touted as a key to their success.
Even today, it is still common to hear people say, “I don’t drink ML wines,” despite the fact that this technique is centuries old, and is, unbeknown to its critics, used on nearly all of the world’s reds, and most of the greatest whites.
So what exactly is ML, and how did it become so maligned?
Although wine has been made for thousands of years, up until only recently winemaking was more black art than science.
Early vintners knew that if they crushed grapes and left the skins and juice together to sit in a vat, within a few days it would slowly begin to bubble. This process would accelerate until there was such a great quantity of bubbles and froth coming to the surface of the vat that it actually seemed to be boiling, leading vintners to dub it “fermentation” (from the Latin word fervere, to boil).
But then, just as quickly as it had started, this mysterious process tapered off and stopped. What had begun as sweet grape juice, however, was now a tart and pleasantly alcoholic drink, aka wine!
Prior to the mid-1800s, what caused this to occur was variously attributed to everything from “God’s Will” to “spontaneous generation,” the scientific theory of the day. It was only then that Louis Pasteur discovered that it was the naturally occurring yeast cells on the outside of the grape skins that were converting the grape sugars into alcohol and carbon dioxide.
Through the Middle Ages, most wine was rushed to market as soon as fermentation had stopped, regardless of taste (Beaujolais Nouveau anyone?). But some vintners realized that if they could keep the wine in barrels until the following summer, its taste would gain in complexity and richness.
Observant cellarmasters noticed that barrels held in reserve often appeared to begin to very gently ferment again in the spring. This secondary fermentation is very subtle — one winemaker likened it to the bubbles coming up in a glass of Champagne that had been left standing for 10 minutes — but the impact on the wine’s taste was notable.
Both reds and whites that had been through this process tasted less acidic, more rounded, and had greater complexity, and, for the whites at least, there was sometimes an extra hint of butter in the taste. As an added bonus, these wines seemed to have a much lower chance of spoiling after they had been sold to customers.
Winemakers attributed this subtle resurgence in cellar activity to a harmonic convergence with the sap rising in the nearby vines — certainly a sentiment that today’s biodynamic adherents could appreciate. It wasn’t until the 1950s that scientists figured out that neither yeast nor cosmic cycles were involved.
Instead, they found that a cold-hating, acid-loving bacteria called Oenococcus was endemic to most wineries, and that once the cellar warmed up in the spring, these bacteria woke up and went to work.
Grapes contain two main types of organic acids: malic (the compound responsible for the tart bite of green apples), and tartaric, an extremely stable acid rarely found in the plant kingdom.
The beneficial bacteria commonly found in wineries will convert the tart malic acid in wine into a combination of the much rounder tasting lactic acid (that found in milk) and a small amount of carbon dioxide (hence the fine bubbling seen during what was traditionally called “secondary fermentation”). This whole process is now known as malolactic fermentation, “malo” — or simply “ML”.
But just as bakers jealously guard their own special-tasting strains of sourdough yeast, there are many different kinds of ML bacteria. In isolating these variants for commercial distribution, researchers have found that some work better in a high-alcohol environment, some are pH tolerant and others generate large amounts of a diacetyl byproduct, the compound that just so happens to be the flavor of buttered popcorn.
Winemakers of course have long had access to a broad palette of tools to influence the final taste of the wine in the bottle. Among countless others, these include how vines are pruned, how ripe to pick grapes, what yeast to use and which barrels to use and for how long. But with the isolation of these “high diacetyl contribution” ML strains — as one winery supply Web site tactfully put it — winemakers were given simple tools to make the notorious butter-bomb wines, even if, as with nuclear weapons, they may have been better off left unused.
This is not to say that malolactic fermentation is bad — in fact, it is one of the most important processes in winemaking, not only for taste (acidic versus round), but also for microbiological stability. Because all wine contains malic acid when it starts its life, and virtually all wineries and wine barrels have native populations of ML bacteria, winemakers are given a choice: either complete a 100 percent malolactic fermentation or perform “sterile filtration,” which forces the wine through a 0.45 micron filter.
“Sterile filtration” removes all the ML bacteria and prevents the wine from disastrously refermenting in the bottle, but it is in itself quite controversial (many winemakers feel that it strips out aroma, and lightens the mouthfeel).
At the end of the day, we like our wines complex and stable in the bottle, so one might even say that we’re mellow with malo, but please hold the butter!