Designation (also Juchtenton or Kerosinton) for a characteristic smell and taste in especially white wine. However, this must not be confused with the firn (Altersfirn). Petroleum clay is reminiscent of mineral oil (kerosene), kerosene or petrol or tanned Juchten leather (leather tanned using birch bark tar). Petrolton occurs mainly in Riesling from physiologically ripe grapes with a high carotenoid content. This is promoted by high exposure (solar radiation), which is why Riesling wines from warmer growing regions such as South Africa and Australia are particularly affected. In the vineyard, attempts are being made to prevent this by reducing defoliation and thus increasing the shade of the grapes. According to studies at the Klosterneuburger Weinbauinstitut, wines from cooler vintages are much less affected by this.
Petrolton is caused by the substance TDN (trimethyl dihydronaphthalene), which is formed during bottle ageing by the breakdown of carotenoids (TDN is not detectable in young wines). Excessively high temperatures during storage and oxidative processes due to, for example, faulty corks or closures can promote the formation. There seems to be a connection with cork tastes, in this respect a faster and increased formation of petroleum tones is observed. To a lesser extent, petroleum tones are perceived as pleasant and positive by certain consumers, but generally in Northern Europe they are perceived as negative. In the southern hemisphere (Australia, New Zealand), on the other hand, it is considered a typical sign of mature Riesling wines. The content of TDN can be extremely increased in very old wines. If critical perception thresholds are exceeded with impairment of the fruit aromas, it is to be considered a wine defect in any case. See also under the age tones Böckser (Lagerböckser), Firn (Altersfirn) and UTA (untypical age tone).