Unexpected wine scents: Petrol
If there's anything that makes people wonder about wine geeks, it's our mysterious ability to detect things like tar, smoke, butter, caramel, bananas, geraniums, and even a whiff of the barnyard wafting from our glass.But gasoline, diesel, or even petrol when we're trying to tastefully emulate our British cousins? In wine? This is a step too far for many people. And yet, it is so common an aroma element in many Rieslings that it takes only one whiff to make the most ardent skeptic a believer.
And then there's Page Two: Granting that these wines really do smell of, er, petrol, how can anyone actually like a wine that reeks of spillage at the service station?
Herein lies one of the many mysteries of wine. First, drop by your local Shell station and take a deep whiff. No, even the most abundantly minerally Riesling doesn't really smell like that. But the organic chemicals that occur naturally in some Riesling grapes and that seem to be brought out by particular growing or winemaking conditions do create a mineral note that strikes our brains in roughly the same place as British Petroleum's finest.
According to a rather geeky article, "Petrol and Riesling," published by the trade association International Riesling Foundation and drawn from the Pacific Rim Winery's Riesling Rules Book, "the petrol note in Riesling is thought to be caused by the compound 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), which is created during the wine's aging process from carotenoid precursors (terpenes) by acid hydrolysis." Got that?
The initial concentration of precursors in the wine determines the wine's potential to develop TDN and petrol notes over time, the article reports, listing the following factors that are thought likely to increase the TDN potential:
● Ripe grapes (accentuated by low yields and/or late harvest).
● High sunlight exposure (a factor that many of the Riesling experts on our WineLovers forum consider the primary cause).
● Water stress, which is most likely in regions that don't practice irrigation. This primarily occurs in dry vineyard sites during warm and low-rain years.
● Warm soils (gravel, etc.)
Coincidentally, the article points out, these same factors are also considered key to growing high-quality Riesling grapes. So by inference, the petrol note is more likely to develop in top Riesling wines than in simpler wines made for the mass market.
"Riesling grown in warmer climates such as Alsace," the article said, "will tend to exhibit the petrol character earlier in their post-bottling development."
And here's the money quote: "A discreet amount of petrol aromatics is a great enhancer, too much can be a bit of a turn-off."
We agree.