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WINEMAKING front, especially with red grapes that can sit in cold soaks for up to 96 hours, you're risking bacteria that can create acetic acid (and its telltale taint of vinegar) or wild yeast that produce ethyl acetate (which smells like nail polish remover). Doug Shafer learned the hard way what can happen when grapes go through the crusher without sulfur: "I had 3,000 gallons of Mer- lot go into spoilage in a heartbeat." Although 97% of the grapes did just fine, one tank of Merlot did not. "Lactobacillus took over and outperformed our yeast. It was on its way to vinegar," he recalls. Though Shafer managed to salvage the tank in the end, he learned his lesson, "and lessons like that stick with you for 35 years." Sulfur dioxide levels typically drop to negligible levels by the end when it comes to adding sulfites, strategies vary by grape variety and winemaker style, yet some general principles apply. The U.S. legal maximum is 350ppm total—a fraction of the 2,000ppm limit for apricots, recommended by the World Health Commit- tee's food code committee. However, Katchmer says, "you usu- ally only see that when someone really screwed up." Most winemakers usually add sulfur dioxide at the crusher at levels anywhere from 20ppm to 50ppm to suppress the natural flora on the grapes, Katchmer explains. By not adding SO2 up of primary fermentation, so unless the winemaker plans a secondary or malolactic fermentation—typical for most reds and some whites— it's time for a second dose. Katchmer adds, "What you're looking for then is a certain level of free SO2 ," which might require a few steps, because some sulfur will bind to other components in the wine. In wine, sulfur dioxide exists in its free form as molecular bisulfate and sulfite, depending on the wine's acidity. And at wine's pH, the most dominant species by far—from 90% to 98%—is bisulfite. But it's the molecular form that is antimicro- After fermentation, one of the primary reasons to add sulfur dioxide is to control spoilage microorganisms. Barrel-aged red wines are particularly susceptible to Brettanomyces, a ubiquitous yeast known for its funky, barnyard aromas. Adding sulfur di- oxide at strategic intervals during the course of barrel aging can either kill or inhibit the odiferous microbe. bial, so winemakers can spend a lot of time measuring free vs. total SO2 levels to make sure they're on track. "Their job is just a lot tougher." —John Katchmer of sulfite-free winemakers By the time the wine is ready for bottling, Katchmer says, most wineries are looking at free sulfite levels around 25-35ppm—lev- els that only the sulfite-sensitive individual would ever notice— and possibly as low as 5-10ppm after a few years in the bottle. Red wines usually need less sulfites than whites, because their tannins help protect the wine from turning brown and stale. Still, for the average consumer who can't shake an aversion to sulfites, no one says it's impossible to make wine without them. "Their job is a just a lot tougher," says Katchmer. And if stray lactic acid bacteria—unchecked by sulfites—gain a foothold just before bottling, they can produce compounds (called biogenic amines) that researchers think trigger bad reactions in humans, including, it seems, the headaches so many pin on sulfites. Liza Gross is a San Francisco-based science journalist and senior sci- ence writer and editor at PLoS Biology. Her features have appeared in the science journal PLoS Biology, High Country News, Tikkun and Sierra. Experience Matters in Winemaking Just as in the making of world class wines, experience counts when designing, building, and supplying winery equipment. With over 50 years of experience in the food and beverage business, Parkson offers customized engineered solutions for the wine industry: - - Liquid-solid separation Conventional and biological wastewater treatment - Waste and biosolids handling Visit us at the 2011 Unified Wine and Grape Symposium (booth #2606). QSEE US AT UNIFIED, BOOTH #2606 58 Wines & Vines JAnUARY 2011 QSEE US AT UNIFIED, BOOTH #1164g FB@parkson.com 1-888-PARKSON www.parkson.com