Goût de pétrol is the French term for an aroma of petroleum or gasoline that can arise during the ripening of Riesling wines, but also due to heat stress in the vineyard. In old Riesling wines the ‘goût de petrol’ is often a desirable characteristic, whereas in young wines it is more often experienced as a wine fault. The aroma is caused, among other things, by the substance 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) that is produced during the ripening process (in the bottle) from carotenoid precursors (the yellow pigments in the skin). The concentration of these carotenoid precursors is particularly high in grapes that 1) are ripe, 2) have a high acidity, 3) have had (too) much sunlight, or 4) have suffered from drought stress. It is therefore a substance that occurs particularly in high-quality Riesling grapes, because these are ripe, have acids, have a lot of sugars and are concentrated.