Forest fires taint wine, now scientist understands how

Forest fires in Australia, California and South Africa can be devastating to people, but the smoke has an insidious effect on wine. All the smoke in a vineyard from a fire makes its way into the grapes making them taste smokey. The smoke is different to the toasty, smokey aromas of a barrel or the smokey notes you can get in, say, a Chablis. It is more like an ashtray taste to the wines that is generally classed as quite unpleasant.
Until now scientists were unsure how, after the fire had ended and the undamaged vineyard looked fine, the grapes tasted great. Yet, after fermentation, a horrible ashtray smell/ taste would evolve.
Professor Wilfried Schwab and his team, from the Professorship for the Biotechnology of Natural Products at the Technical University of Munich, published the cause in the Journal of Agricultural and Food Chemistry. According to their findings if the vines are exposed to smoke, the grape vine absorbs the smokey aromas via its leaves and fruits. In the plant, the off-notes are then linked with sugar molecules by a glycosyltransferase. This link with sugar molecules makes the smokey off-notes more water-soluble. As a result, the grape vine stores the now no longer volatile smoke aromas. However during fermentation those sugars are converted to alcohol and the smokey ash taste is released.