Q: I've noticed that natural wines—unfiltered, with no additives—are really popular right now. Some of them appear cloudy, and proponents talk about the wines' "naturally occurring microbiology." Does that mean that they could have bacteria growing in them? Is it possible to get food poisoning from drinking unfiltered wine?—Candace D., Portland, Ore.
A: To answer this question, we turned to Isabelle Legeron, a certified Master of Wine, author of Natural Wine: An Introduction to Organic and Biodynamic Wines Made Naturally (CICO Books, 2014) and the founder of Raw Wine, a wine fair dedicated entirely to natural wines:
We're not used to thinking about wine as a food. And yet that is exactly what it is—a product of fermentation, very much like kombucha or kefir or indeed cheese. Millions of bacteria work alongside yeast to ferment grape juice into wine. Like yeast, these bacteria cover berries and line cellar walls. Lactic acid bacteria (LAB) and acetic acid bacteria (AAB) are, I believe, the only families of bacteria [consistently] found in grape must and wine. LAB in particular is a very beneficial strain—think of the probiotics in live yogurts—and plays a fundamental role in creating wine. It carries out a secondary fermentation called malolactic fermentation during which malic acid, which occurs naturally in grape juice, is converted into the softer lactic acid, so changing the texture and flavor. As Gilles Vergé, a grower in Burgundy once explained to me: "Without bacteria, wine cannot age. It's they that keep freshness going even in very old wines. They can continue to evolve for decades, if not centuries. They don't need much to survive, just the trace sugars that remain after fermentation."
[Editor's note: Acetic acid bacteria (AAB) convert ethanol to acetic acid, also known in wine parlance as "volatile acidity," or VA. At high levels (above 0.1 percent), it is considered a wine flaw, and in mainstream commercial winemaking, the growth of AAB is typically controlled by the addition of sulfur dioxide.]
Wine's low pH and its alcohol content mean that, overall, it's a pretty inhospitable environment for bugs. While some bacteria can create what are considered "off-flavors," there are none that I am aware of that are harmful to human health. On the contrary, some research even suggests that wine's live organisms might actually be good for us. ... Yes, [natural wine] can sometimes be a little cloudy, but hopefully that means it is full of naturally occurring microbiology.