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WINEMAKING Researchers still don't know how sulfites trigger adverse reac- tions in asthmatics. One seductively elegant theory surfaced when a 1986 study found lower levels of sulfur oxidase—an enzyme that con- verts sulfur-containing compounds into a form that the body excretes—in the skin cells of sulfite-sensitive patients. But further investigation failed to implicate sulfur oxidase deficiency for most people, says Taylor. "It might be a multifactorial thing where a few people have this mechanism, and others have an- other mechanism." Since the FDA outlawed sulfite sprays on fresh foods and required labels on prepared products in 1986, it has received far fewer complaints of adverse reactions and no reports of fatali- ties. Taylor blames salad bars for most of the problems. "The severe episodes paralleled the development of these salad fresh- eners," he says. "I think they're the smoking gun." Where food processors and winemakers added sulfites in prescribed, consis- tent amounts, levels at restaurants were large and uncontrolled, typically applied by an hourly employee. Restaurant workers, says Taylor, "were just throwing handfuls of this stuff in there." A molecular guardian Not so long ago, with somewhat crude and imprecise methods for handling sulfur dioxide, winemakers often relied on trial and error to get the levels right. Hindsight suggests that tradition favored a heavy hand. Back in the late 1970s early '80s, people tended to use more sulfites as a general rule, says Doug Shafer, president of Napa's highly regarded Shafer Vineyards. "When grapes would come in, you'd hit them with 100ppm sulfites at the crusher" to control wild yeasts and spoilage bacteria. Over time, people learned that just 20-30ppm would produce the same effect. Nowadays, Shafer says, the goal is to use as little as possible. Microbiologist Linda Bisson from the University of California, Davis, thinks sulfite use was much higher several years ago, in part because sanitation wasn't as good and people weren't using refrigeration, "so they really had to knock out spoilage micro- organisms." But with technological improvements and a better understanding of what sulfur dioxide really does and when, "you don't have to dump in the SO2 ." ogy consultant at Vinquiry, a private wine laboratory. And if you're trying to control undesirable organisms during fermentation, Bisson explains, simply inoculating with healthy yeasts can work wonders. In her undergraduate winemaking class at UC Davis, Bisson demonstrates sulfur dioxide's antioxi- dant properties with a simple experiment. She has students add from zero to 200ppm sulfur dioxide with and without native yeasts and with and without inoculations of Saccharomyces, the yeoman's yeast of efficient fermentations. "They generally see that you don't need the SO2 "If you know your fruit, and your fruit is clean—and you know your winery, and your winery is clean—there's no reason why you need to have a lot of SO2 ," says John Katchmer, enol- lating, because you're giving Saccharomyces a boost to take over. But if you don't add SO2 and you do a native fermentation, those 56 Wines & Vines JAnUARY 2011 QSEE US AT UNIFIED, BOOTH #112 often stick," or stop fermenting, largely because the spoilage mi- crobes hijack the initial fermentation. The experiment reveals that sulfites prevent the bad microbes' enzymes from consuming the oxygen that Saccharomyces needs to do its job. "Saccharomyces is happier because it's getting the oxygen and enzymes aren't." It's nearly impossible to find wines with absolutely no sulfites, because yeasts naturally produce SO2 during fermentation. And if you're inocu-