Petrol in Your Wine? Understanding This Unique Aroma
In the world of fine wines, petrol notes are a distinct hallmark found in aged varieties, particularly those stemming from grapes teeming with a group of chemicals known as terpenes. Notable grape varieties like Muscat, Riesling, Gewurztraminer, and Torrontes boast high levels of terpenes such as nerol, linalool, and geraniol. These terpenes are the virtuosos behind the grapes’ intense aromatic fragrances, evoking sensations of roses and citrus fruits.
The Role of UV Light: Enhancing Terpene Concentration
A pivotal factor in the amplification of terpene concentration in grapes is their exposure to substantial levels of ultra violet (UV) light. Winegrowers often employ strategic viticultural methods to maximize sunlight exposure on the grape berries, enhancing their terpene profile.
The Chemical Choreography: From Terpenes to TDN
This increased UV light exposure fosters the synthesis of terpenes and other molecules like carotenoids, the same compounds responsible for the orange hue in carrots. Both carotenoids and terpenes originate from similar chemical precursors. As wines age, these precursors evolve into a compound known as 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), the architect behind the wine’s petrol aroma.
The wine’s inherent potential to develop TDN and its characteristic petrol notes are contingent on the initial concentration of these precursor chemicals.
Key Factors Influencing TDN Formation in Grapes
- High Light Exposure
- Ripe Grapes: Enhanced by low yields or late harvests
- Water Stress: Common in regions where irrigation is not practiced
- Warm Soils: As found in vineyards with gravelly terrains
These conditions predominantly arise in dry vineyard locales during years characterized by warmth and scant rainfall.
Interestingly, these factors are often synonymous with the production of high-quality grapes, explaining why many top-tier terpene-rich wines also possess pronounced petrol notes.