Q: Does unfiltered wine contain harmful bacteria?—Chelsea, Hendersonville, N.C.
A: Most wines are filtered to remove leftover particles of grape skins, seeds, stems, etc., as well as spent yeast cells and other lees that can cause wines to appear cloudy. Filtering also helps ensure that a wine remains stable after bottling, but some winemakers believe it can strip a wine of flavors and aromas. Whether or not to filter a wine is strictly a matter of taste, however, and there are no known health risks associated with unfiltered wine vs. filtered wine.
"Wine is considered a hostile environment for most bacteria," Dr. Anita Oberholster, an associate specialist in cooperative extension in enology at U.C. Davis, told Wine Spectator, explaining that both the presence of alcohol and the low pH are antibacterial factors. "The bacteria that survive in wine is only a potential concern for wine quality, not for human health."
According to Isabelle Legeron, a certified Master of Wine, author of Natural Wine: An Introduction to Organic and Biodynamic Wines Made Naturally and the founder of the Raw Wine fair, lactic acid and acetic acid bacteria are the only families of bacteria consistently found in grape must and wine, and are rather beneficial toward health and creating great wine.
Some scientists even argue that filtration can reduce the concentration of phenolics in red wine, known for their potential health benefits, but there are few studies that compare filtered and unfiltered wines. Please consult your physician before incorporating moderate wine consumption into your diet.—Shawn Zylberberg