Where grapes and wine can run into trouble is that while these sugar-attaching enzymes are very effective, they are not very picky. A glycosyltransferase doesn’t care much (and can’t tell) if an aroma molecule it encounters was made inside the grape, or if it got diffused into the grape from the outside, especially if it has some structural similarity to molecules the grape does make on the regular. In the normal run of things, a grape makes some flavor molecules and a glycosyltransferase catches them and turns them into glycosides. In the case of wildfire smoke exposure, flavor molecules (this time, smoky ones, rather than ripe fruity ones) diffuse into the grape, get picked up by the glycosyltransferase enzymes — as if they were the grape’s own flavor molecules — and are packed away in hidden, scentless, glycoside form.
Source: latimes.com – Los Angeles Times