Forest fires cause havoc for lots of reasons. But something you’ve probably never thought about is what they do to wine. Yep, they ruin it – grapes grown near forest fires make wine that tastes like ash, and it's only detectable after the finished product, which is far too late. Now, researchers know why and are hoping to save winemakers from this terrible problem.

Basically, when grapes grow near fire, smoky aromas get inside them, and these aren’t smoky aromas of the good kind. The molecules become attached to sugar, making them more water soluble, and disguising them from our senses. This is all due to an enzyme called glycosyltransferase.

The enzyme shouldn’t really be processing smoke aroma molecules at all, but it does, and researchers from the Technical University of Munich (TUM), Germany, now know why. Their findings are published in the Journal of Agricultural and Food Chemistry. 

Glycosyltransferase is meant to process something in grapes called resveratrol, which has health-promoting properties. Structurally, resveratrol is similar to smoky aroma molecules, so the enzyme treats them in the same way.

Because the molecules in the grapes are bound to sugar, we can’t detect them. But when yeast is added to ferment them and make wine, a problem arises. The process separates the sugar and aroma molecules so that the unwanted flavor develops in the wine.

"Therefore, it only becomes apparent in the finished wine that the vineyard was exposed to a fire and the final product is of poor quality," said lead author Katja Härtl in a statement.

This is a real problem for vineyards in places like California, Italy, and Australia, and the new findings could be used to prevent it in future.

"We now know how such a taste can develop," said study author Professor Wilfried Schwab. "In the next step, we can try to cultivate either grape vines with less glycosyltransferase. Or we'll add a second sugar to prevent the release of the bad aromas."

Another solution is that yeasts that don’t release the smoke aromas could be used or the yeast could be genetically modified. Anyway, in future winemakers should be able to avoid the issue, ensuring good quality wine all round. Yay!