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Some wines, like those aged in toasted oak barrels, taste great with a hint of smoke. But too much can spoil the flavor. As the climate warms and wildfires grow more frequent and intense, pollution from them can drift into vineyards and get absorbed by the plants—imparting a foul, ashy taste known in the industry as “smoke taint.” Bushfires between 2006 and 2007 ruined around $60 million to $70 million worth of wine in the Australian state of Victoria alone. This year late summer wildfires damaged grapes in Oregon and Washington State and, in a tragedy that killed dozens, devastated parts of northern California.
Little is known about the biochemistry of how smoke contaminates wine. Adding to the mystery is that smoky notes cannot always be tasted in the grapes themselves—but they still sometimes find their way into the finished product. Recent research, however, helps explain what is going on. In a study published in July in the Journal of Agricultural and Food Chemistry, Wilfried Schwab, a food chemist at the Technical University of Munich, and his colleagues identified a type of grapevine enzyme called glycosyltransferases, which bind smoke molecules to sugars in the grapes. This creates chemicals called glucosides that are difficult to taste but can be broken down by yeast during fermentation, freeing the ashy notes and ruining the wine.
The discovery points to some possible fixes for the pungent problem. One option is to breed or isolate strains of yeast that leave the glucosides intact. Another strategy is to develop a chemical that deactivates glycosyltransferases and could be sprayed on vines. This would prevent sugars from binding to and locking up the acrid flavors within the plant, says Markus Herderich, a scientist at the Australian Wine Research Institute, who was not involved in the Munich work. Scientists might also be able to find grape strains with low natural levels of glycosyltransferases—or even to genetically engineer plants that lack such chemicals. The search for solutions, Schwab says, is on.
