Who has not at some point felt petroleum aroma in a wine, most likely in a riesling? This slightly odd aroma is often associated with older, mature riesling. There has been discussion about where the aroma actually comes from.
And is a petroleum-scented riesling attractive or not? Well, opinions differ. It seems that either you love it or hate it.
The excellent Seven Fifty Daily has attempted to explain the phenomenon.
Petroleum comes from an organic compound called TDN (1,1,6-Trimethyl-1,2-dihydronaphthalene). The formation of TDN in wine is due to the carotenoids found in grapes.
Carotenoids are a type of organic nutrient and coloring agent found in carrots, among other things. When carotenoids break down, two types of non-volatile TDN precursors called C13-norisoprenoids can form in a riesling. These precursors eventually form (volatile) TDN.
However, it takes time, which is why the petroleum aroma often only appears after several years. Acidity plays a key role in these changes, so riesling wines with higher acidity tend to develop TDN more quickly.
More sunlight means more carotenoid production, so if the producer wants to avoid petroleum, he should protect his vines from too much sun. This is also important to consider in the light of climate change.
Read more interesting things about wine and petroleum here: sevenfifty
