Petroleum notes in aged Riesling wines

 

With time, Riesling wines tend to acquire a petrol note[16] (goût petrol in French) which is sometimes described with associations to kerosene, lubricant or rubber. While an integral part of the aroma profile of mature Riesling and sought after by many experienced drinkers, it may be off-putting to those unaccustomed to it, and those who primarily seek young and fruity aromas in their wine. The negative attitude to aromas of mature Riesling, and the preference for young wines of this variety, seem more common in Germany than in Alsace or on the export market, and some German producers, especially the volume-oriented ones, have even gone so far as to consider the petrol notes a defect which they try to avoid. In that vein, the German Wine Institute has gone so far as to omit the mentioning of "petrol" as a possible aroma on their German-language Wine Aroma Wheel, which is supposed to be specially adapted to German wines, and despite the fact that professor Ann C. Noble had included petrol in her original version of the wheel.

 

 

The petrol note is considered to be caused by the compound 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN),[17] which during the aging process is created from carotenoid precursors by acid hydrolysis. The initial concentration of precursors in the wine determines the wine's potential to develop TDN and petrol notes over time. From what is known of the production of carotenoids in grapes, factors that are likely to increase the TDN potential are:[16]

  • Ripe grapes, i.e., low yields and late harvest
  • High sun exposure
  • Water stress, which is most likely in regions which do not practice irrigation, and there primarily in certain dry vineyard sites in hot and dry years
  • High acid content

These factors are usually also considered to contribute to high quality Riesling wines, so the petrol note is in fact more likely to develop in top wines than in simpler wines made from high-yielding vineyards, especially those from the New World, where irrigation is common.