Aromatic CompoundStructure
Confusion risk: Riesling · Chenin Blanc · Grüner Veltliner
The Gist
That gasoline or kerosene note in older Riesling is a real compound called TDN — not a flaw. It builds up with age and sun exposure, so it's loud in mature or warm-climate Riesling and quiet in young Mosel. If you smell petrol in a white wine, you're almost certainly looking at Riesling.
Mechanism
TDN is produced by the oxidative degradation of carotenoids in grape skins — particularly under high UV exposure and warm conditions. In Riesling, a natural abundance of carotenoid precursors means TDN levels increase significantly with age and with warmer vintages. The compound smells unmistakably of petroleum, diesel, or kerosene. It is not a fault. It is one of the most reliable chemical identifiers in all of wine tasting.
TDN increases with age and with sun exposure. Clare Valley Riesling develops TDN faster than Mosel. Young Riesling may show only faint petrol; older Riesling can be dominated by it. If you smell petrol in a white wine, no other Pour Advice-testable grape produces it at this intensity.
Deeper mechanism
Riesling is not the only grape that produces TDN — Chardonnay and Gewürztraminer can show trace amounts — but Riesling's carotenoid concentration is exceptionally high, making its TDN levels diagnostically distinct. Young Mosel Kabinett may show no TDN at all; this is why understanding the alcohol level (very low) and acidity (very high) as backup identifiers is critical when TDN is absent.
Confusion analysis
Riesling vs. Chenin Blanc (off-dry)
The most common Advanced exam confusion. Both: high acid, off-dry, pale, stone fruit. TDN is the escape hatch — Chenin never produces it. If no TDN: check alcohol (Riesling is lower) and waxy/lanolin texture (Chenin only).
Dry Riesling (Trocken/GG) vs. Grüner Veltliner
Both Austrian/German, both high acid, both herbal-mineral. Riesling: TDN, jasmine, no pepper. GrüVe: white pepper (rotundone), no TDN, no jasmine. If TDN present: Riesling. If white pepper on finish: GrüVe.