Wildfire smoke obscures the sun in Oregon.
Wildfire smoke obscures the sun in Oregon. Mark Gunn/CC BY 2.0

As grape harvest begins, winemakers up and down the West Coast are nervous. The thick smoke smothering the region, a result of a particularly bad fire season, threatens the quality of their crops. While a subtle smokiness can be a nice flavor in a French Oak-aged Chardonnay, most wine drinkers don’t want a Pinot or a Riesling that tastes like an ashtray. But that’s what they could end up with, thanks to some interesting chemistry in the grapes, recently described by a team of German researchers.

Ironically, it’s the grape plant’s attempt to isolate the smoke molecules that allows the smoke flavor to come through in the finished wine. When grape plants absorb smoke molecules, they attach a sugar molecule to the foreign substance to render it inactive and make it more water-soluble. If you found yourself in a vineyard that had been cloaked in smoke and ate a grape straight off the vine, you wouldn’t notice anything different about the berry. It isn’t until the grape juice goes through fermentation, and the yeast breaks up those sugars, that the smoke molecules are released again. Just the final product contains any clue that wildfires burned near the vineyard.

Unfortunately, winemakers can’t do a thing about their wine tasting like ash. But now that scientists understand exactly why the flavor occurs at all, they can start to work on a solution. The answer may be to engineer a yeast that ignores sugar attached to smoke molecules, or it may be to use grape plants that produce less of the enzyme responsible for binding the sugar and smoke. A fix is probably not coming soon, though, and certainly not soon enough for this year’s vintage.