Driftless Terroir: Malolactic Fermentation Makes Wines Yummier

Erik Flesch

If you wanted to dip a glass into this magical place where we live and to drink deeply of it, what do you imagine it could taste like? Is it bright and acidic or rich and buttery? The flavor you experience comes down to the choice of a winemaker. Some of us have well-defined preferences of one or another. But if we want to figure out which choice is more indicative of the particular distinct character of the Driftless Area, in other words to identify the influence of terroir on the flavor of Driftless-made wines versus the influence of the winemaker or some other influence, we have to talk about malolactic fermentation. Malic acid is the tart acid in grapes also found in green apples. Lactic acid, on the other hand, is the more creamy acid found in milk, cheese and yogurt. Here in America’s Dairyland, this is a cool kind of fermentation to be familiar with.
The flavor of wine is controlled not only by yeast, which is a fungus, but also by bacteria. Scientists as recently as Louis Pasteur did not yet know this. Yeasts convert sugar to alcohol in the first fermentation, but a second parallel malolactic fermentation is just as important in controlling flavor and aroma. The ML process converts malic acid, which is associated with the taste of green apples, into lactic acid, which has the flavor and aroma of buttered popcorn. Some white wines do not benefit from ML, such as German Riesling or Gewürztraminer, and the winemaker takes steps to prevent it; however, for other whites like Chardonnay, ML can add important defining character such as in barrel-aged buttery “California-style” Chards. Red wines all benefit from ML, which tend to be harsh and astringent prior to malolactic fermentation. After the malic acid is converted to lactic, the wine becomes noticeably softer and more approachable, and is perceivably heavier and rounder on the palate.

Malolactic fermentation is the natural process by which malic acid in wine is converted to lactic acid by the bacteria oenococcus oeni.

Here in the Driftless Area, we cannot always rely on winemaking practices typical of other places because we have to plant cold-hardy varietals that are relatively new hybrids. Our grapes are crosses between American vitis labrusca or vitis riparia grapes, which provide survival strength, and European vitis vinifera, which contribute nuance to the flavor — and the sum total of our environmental factors bring interesting challenges to bear. Grapes grown in cool climates like ours — grapes like Brianna, Edelweiss, Frontenac, LaCrescent, Lacrosse, Léon Millot, Marquette, Prairie Star, Seyval Blanc, St. Croix, St. Pepin, Marechal Foch — tend to be high in acidic flavor, much of which is contributed by malic acid, and low in tannins. To the extent that the growers and fermenters of grapes are among those creatives who give definition to the flavor of place, the choice to encourage or discourage ML flavor profiles is important. How do we keep the flavor identity of our unique varietals distinctive while also making sure they are premium quality and flavorsome?

When you taste a sip of wine, if the mouthful of place you taste is pleasantly tart like an apple, you might pucker and smack your lips and say, “Fresh!” But on the other hand, if the acid is so strong that you can barely take it and the winemaker has to cover up the flavor with extreme sweetness to bring some other experience to the party and make it barely palatable, you might identify that character as a fault and wish we had more tools in our region’s winemaking toolbox.
An ongoing release of new grapes by research programs like the University of Minnesota’s challenges our current generation of Wisconsin winemakers to learn by doing in real time and to dream up poetic new vintages that bring style and refinement to the fruit. This newness can challenge us consumers and wine enthusiasts to build a bridge of trust with the growers and winemakers and to experience the identity of our region anew through the flavors in the bottle. For example, if you tasted something balanced and soft with the aroma of butter, you might say “Rich!” because the winemaker decided to take some of that acid and turn it into the flavor and aroma of butter. But it takes the bacteria oenococcus oeni to make it happen.
Some might argue that whether or not to ML is a spiritual matter. The art and science of harnessing microbiotica for human enjoyment is exciting and controversial. It predates the knowledge of yeasts, molds, fungi and bacteria to the time when philosophers attributed spiritual causations to human experiences. The early 20th-century spiritual philosopher Rudolph Steiner created and launched “biodynamic” farming — a specific form of agriculture that has come to be regarded as “premium organic,” but involves working with the cosmos, earth and spiritual entities as part of a comprehensive picture of the complex dynamic relationships at work in nature. He advocated abandoning chemical fertilizers that could sterilize the land and instead to focus on developing the life spirit in the soil. Today, many interpret “life spirit in the soil” to be microbiotica: yeasts, mold, fungi and bacteria. The microbial life in the soil catalyzes the magic of plant fertilization as well as the fermentations that flavor and preserve our local foods and beverages. Strict organic/biodynamic winemakers strive to allow all fermentation and flavor development to derive exclusively from vineyard-specific microbes. That high standard can be difficult in our region, in which powdery mildew and other pathogens must be controlled with spraying to get a bank loan and even to ensure a harvest at all. That means winemakers need great options for lab-grown strains of bacteria that they can order to predictably control how the wine will taste but still represent our region’s native flora. There may be opportunities for scientist entrepreneurs to identify and mass-produce such strains, but in the meantime, there is no dishonor in experimenting with malolactic cultures that are already available.
A terroir-sensitive approach to winemaking tends to be a holistic one that understands and celebrates our context of place. It focuses on the relationship between soil health, vine health, grape quality — and winemaking techniques that are relatively minimalist, yet purposeful. They consider every vineyard to be unique, which means the relationship between bedrock geology, soil, solar orientation and microclimate has the potential to produce a different result at every location. To the extent possible while ensuring a decent crop, for the vines to capture these unique characteristics of their site with their roots and their leaves, the soil must be alive and healthy and the leaves must be inoculated with the microbes of that place. If processes like ML can’t be successful and high quality with exclusively native flora, they seek cultivated options that clearly relate and make delicious-tasting wines that present a true, original and authentic expression of this place.

Erik Flesch is the director of The Mining & Rollo Jamison Museums. He is a geologist and an architectural designer trained at Taliesin, the Frank Lloyd Wright School of Architecture. He lives in Mineral Point with his wife, Sara, and can be reached at erik@driftlessterroirstudio.com.