“Fermentation is nature’s way of recycling nutrients back into the soil. Microorganisms sit on the berries, waiting for access. When these finally drop, the berry’s protective skin cracks and in go the microbes to break it down, returning its components to the soil so that they can be taken up by plants once again.”
(HANS-PETER SCHMIDT, FROM THE MYTHOPIA VINEYARD, SWITZERLAND)
Fermentation happens when yeasts, bacteria, and other microorganisms break down complex organic compounds (i.e. plants, animals, and other stuff made of carbon) into smaller chemical components. It is a process of decomposition and, in the case of wine, is the single most important part of vinification. It is here that sweet grape juice is transformed into an alcoholic drink and when many of the aromas that make wine so interesting are born. Left to its own devices, fermentation is usually a two-stage process in which alcoholic fermentation (by yeasts) is followed by malolactic fermentation or malo (by bacteria).
Miraculously, these agents of change occur all around us. For example, there are around one million bacterial cells in a milliliter of fresh water and tens of millions of yeast cells in a milliliter of healthy, organic grape juice. Little wonder, then, that “by the time we are fully grown, we have a 3-pound organ of ‘others’ inside our guts,” says Carl Zimmer, science writer for the New York Times. Some are benign, a few are pathogens, and many are essential to our well-being.
Having fermented foods at home, and produced several thousand bottles of wine, I have an immense respect for these invisible soldiers that crack on with their task spontaneously, producing great transformations and delicious, live flavors. Leave flour and water on your kitchen counter, for example, and a culture for sourdough bread will start up. Leave grape juice in a bucket and it will become wine, or perhaps vinegar, depending on which microorganisms take hold. In fact, both yeasts and bacteria play a key role in making some of the most exciting foods we know, including cheese, salami, beer, cider, and, of course, wine. Certainly, not all yeasts or bacteria are always desirable, but, if you strengthen those that are good, they usually have a fighting chance of conquering and guarding the space they come to occupy.
Healthy grapes from a healthy vineyard spontaneously ferment if left to their own devices.
Yeasts are invisible fungi capable of exponential reproduction when in the right place at the right time. More specifically in the case of grapes, yeasts are found everywhere, from the soil to the vines to the cellar. Their job is to consume sugars in the grape juice, releasing alcohol as a by-product, alongside carbon dioxide and complex flavor compounds. They are the crux of natural wine. They are part of the terroir, along with soil, grape, climate, topography, etc. Yeast populations vary from year to year as a result of environmental factors, so contributing to what is known as vintage variation (see The Vineyard: Understanding Terroir, pages 40–43). These diverse populations kick in at different stages of the fermentation process in a domino effect that sees a new yeast pick up where an older one leaves off. In particular, the sugar-loving Saccharomyces cerevisiae yeast, so essential in baking and brewing, is quick to take over from other yeast strains and fundamental to the production of wine.
Yeasts find strength in numbers. An abundance of yeast is necessary to carry out an effective natural ferment, while using a diversity of strains results in layers of different flavors in the end wine. As Pierre Overnoy, from the Jura, a region in the east of France, explains, “When the official 1996 harvest day was declared, we measured our yeast population. It was 5 million cells/ml (equivalent to a drop of juice). Lots of our neighbors started harvesting, but we held off for a week, until the population had reached 25 million/ml.” For Pierre, who does not add sulfites at any stage, the health and size of the yeast population were paramount. “In order to avoid problems during fermentation and achieve great complexity of flavor, you need as many yeast as possible.”
Natural fermentations can take longer than conventional ones because the growers are working with unpredictable wildlife. The fermentation can last from as little as a couple of weeks to several months or even years.
What conventional producers do differently: These producers often eliminate indigenous yeasts (using heat, sulfur dioxide, and filtration, etc.) to inoculate lab-bred strains that have been tested to reduce risk, encourage specific flavors, and speed up production. “It’s interesting to see the parallels between the descriptions used by yeast manufacturers and those used by the wine trade when describing terroir,” says Nicolas Joly, who advocates spontaneous fermentation. “Consumers should be told that the aromas in wine are often added in the cellar.” Indeed, brochures for commercial yeasts certainly make for interesting reading:
BM45—Italian isolate recommended for Sangiovese. Contributes higher acidity, low astringency, and... great mouthfeel... Brings out aromas described as fruit jams, rose petals, and cherry liqueur, with notes of sweet spices, licorice, and cedar… perfect for creating traditional Italian wine styles.
CY3079—“Classic” white Burgundy: floral notes, fresh butter, toasted bread, honey, hazelnut, almond, and pineapple... rich and full mouthfeel.
Airlocks at Tony Coturri’s vineyard in California. Inserted into the tops of barrels, they allow carbon dioxide to be released during fermentation.
Spontaneous fermentation.
Ridding the barrel of grape solids after racking off freshly fermented wine.
Tasting tank samples to monitor the wine’s development.
Millions of bacteria work alongside the yeasts. Like yeasts, they cover berries and line cellar walls. One key beneficial strain called lactic acid bacteria (or LAB)—think of the probiotics in live yogurts—plays a fundamental role in creating wine. It carries out a secondary fermentation called malolactic fermentation (or malo) during which malic acid, which occurs naturally in grape juice, is converted into the softer lactic acid, so changing the texture and flavor. Although not strictly speaking a fermentation, it is referred to as such because of the bubbling effect of the CO2 that is released during the transformation.
Natural wines mostly go through malo because, left to their own devices, the bacteria will take over once the yeasts have finished the alcoholic fermentation (although sometimes this can happen before the end of the alcoholic fermentation, which is risky as it can lead to volatile acidity). Occasionally, though, malo doesn’t kick in, especially in wines with a low pH, which can be the result of a specific year or grape variety.
The other main bacteria that can be found in wine are acetic acid bacteria. These bacteria ferment ethanol, producing acetic acid and giving off what is known as “volatile acidity” (see Misconceptions: Wine Faults, pages 78–79), which, if dominant, can spoil the wine and potentially turn it to vinegar.
What conventional producers do differently: Many conventional winemakers actively block malo in order to create a particular style, especially if they are striving for a zippy, zesty white wine. It is about taking a step away from nature toward a stylized product.
Producers block malo by chilling the wine, filtering out or killing the LAB by adding sulfites, or using strains of commercial yeasts like Lalvin EC-1118, which are selected for the unusually high levels of sulfur dioxide they give off during fermentation.
Personally, I believe that blocking malo hampers the development of a wine. It robs the drinker of the full flavor and texture profile that wine is capable of, and those wines that have been purposefully held back in this way often taste as if they have been placed in a straitjacket. Similarly, wines are sometimes inoculated with LAB in order to speed up or control malo.
JUST LET NATURE TAKE ITS COURSE...
Many cellar interventions are related, in some way, to managing the indigenous microflora: to weaken, diminish, or eliminate them, lessen their impact, or compensate for the fact that they aren’t working properly. Healthy, active populations of yeast and bacteria go hand in hand with a healthy vineyard. If you start off with great grapes, covered in micro-life, then, as one grower once told me, “Wine just makes itself.”
All the wines produced by La Ferme des Sept Lunes are fermented spontaneously, and malo is never blocked on any color or style.
