Wine is not just a beverage but an ever-evolving work of art. Each sip tells a story that starts in the vineyard and continues through vinification, fermentation, and aging. Tertiary aromas, which develop during aging, represent the culmination of this evolution, adding complexity, elegance, and depth to the wine's bouquet.
One of the most fascinating aspects of enology is how a wine's bouquet changes with age. Over time, a wine can develop a surprising and pleasing bouquet of aromas or lose its “personality.”
Tertiary aromas are formed during the last phase of a wine's life: aging, which can occur in a barrel or bottle. These aromas chronologically follow the primary aromas of the grape variety (e.g., fresh fruit and flowers), and the secondary aromas, developed during fermentation (e.g., fermentation aromas such as yeast, butter, and lactic notes). Tertiary aromas, also called “aging aromas,” are distinguished by their ability to enrich wine with complex, nuanced, and deeply intriguing aromas.
The origin of wood aromas and wine aging.
Tertiary aromas are the result of a series of chemical and physical processes that occur during aging. The main factors contributing to this transformation are:
- Controlled oxidation: During barrel aging, wood allows a slow and continuous exchange of oxygen, while in the bottle this process is regulated by the cork, which allows micro-quantities of oxygen to filter through. This phenomenon produces notes of dried fruit (nuts, almonds), honey, beeswax, and spices in white wines, and plum, cooked fruit, jam, and tobacco in red wines. Oxidation of wine's aromatic chemical compounds occurs over time in all wines: red, white, sparkling, sweet, and fortified. Oxidation is due to the escape of air through the pores of the wood when the wine is maturing in the barrel and through the cork when the wine is aging in the bottle. The oxidation process is slower in red wines than in white wines and therefore occurs over a longer period, years or even decades. This is because polyphenols, which have a higher concentration in red wines, have pronounced antioxidant properties.
- Interaction with wood: barrel aging enriches the wine with aromatic compounds found in wood. Notes of vanilla, coconut, caramel, coffee, leather, and spices such as cloves are some of the typical characteristics of barrel-aged wines. The size of the barrel, the origin of the wood (French or American oak), and the level of toasting significantly influence the final result.
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Internal chemical processes: Over time, fundamental chemical reactions occur within the wine, generating new aromatic compounds:
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Acetalization: this is the process in which aldehydes and alcohols interact, forming acetals. It is typical in bottle-aged wines and contributes sweet and soft notes, such as honey, toast, and almonds.
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Esterification: is the reaction between acids and alcohols that produces esters. Esters are associated with fruity (e.g., baked apple, dried apricot) and floral scents, especially in white wines.
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Esterification: this is a lesser-known but important process in which complex ethers are formed from alcohols and phenols. This reaction is the basis of the spicy, balsamic, and toasted wood notes characteristic of mature wines aged in barrels.
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Tertiary Aromas in Red and White Wines
Tertiary aromas manifest differently in red and white wines, reflecting the nature of the grape variety and the aging process:
- Red Wines. Aging enriches reds with aromas of cooked fruit (plum, black cherry, jam), leather, tobacco, chocolate, sweet spices (cinnamon, nutmeg), and, in the finest cases, truffle.
- White Wines. In whites, typical scents are honey, beeswax, hazelnut, almond, fenugreek, and resin. Some whites, such as Riesling, may develop unique mineral notes, such as kerosene.
The Impact of Barrel Maturation
Wood plays a crucial role in the formation of tertiary aromas, and its use varies depending on various factors:
- Barrel size. Small barrels, such as 225-liter barrels, provide a greater surface area of contact between wine and wood, intensifying aromas and allowing for more controlled oxidation. Large barrels, on the other hand, provide gentler aging.
- New versus old wood: New barrels release more aromatic compounds, while used barrels let the aromas of the wine itself prevail.
- Area of wood provenance: French oak is known for its elegant, vanilla notes, while American oak tends to impart more intense aromas, such as coconut and spice.
- Type of wood toasting.
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Wood processing.
During barrel aging, some of the fruit/fermentation aromas of the wine are absorbed by the wood, losing intensity. Some grape varieties lend themselves better to barrel aging than others because they also retain fermentative aromas well: Merlot, Cabernet Franc, Cabernet Sauvignon, and Pinot Noir, for red wines; Chardonnay and Sauvignon Blanc, for white wines.
When is a Wine Mature? A mature wine is one in which primary and secondary aromas coexist harmoniously with tertiary aromas. However, when oxidative aromas become dominant, the wine may be perceived as “old” and lose its uniqueness. Good aging ensures that the evolutionary scents do not overpower but complement the bouquet.
Iconic Aromas of Aged Wines.
Some grape varieties are particularly noted for developing unique aromas during aging. Two examples of wines that improve over time and develop specific aromas because they have specific chemical “precursors” that evolve into aromatic compounds easily perceived by our sense of smell are: Riesling, for its kerosene aroma, and robust Bordeaux red wines, for their truffle aroma.
The kerosene aroma in Riesling is due to a molecule called TDN (1, 1, 6, -trimethyl-1,2-dihydronaptalene). The concentration of this molecule in wine increases over time and is higher when grapes are grown in warm areas with high sun exposure. This aroma adds complexity to the wine's bouquet, but it should be subtle and not overpower the other aromas.
The truffle aroma in Bordeaux reds is due to a molecule called DMS (Dimethyl Sulfide). When perceived in high concentrations, DMS has an odor that can be very unpleasant and is often considered a defect in wine, with notes of cooked corn, tomato, and asparagus. However, at lower concentrations, it can enhance the complexity of the wine's aroma with delicate truffle notes. As a Bordeaux red wine ages in bottle, the concentration of DMS increases reaching a peak after 10-15 years. It can be found in many robust red wines, but it is considered a characteristic aroma of the great red wines of the Bordeaux region that are aged 10-20 years.
How to Train the Nose
To identify and appreciate tertiary aromas, it is essential to develop one's olfactory memory. TasterPlace's aroma collections, such as the one dedicated to Wood and Wine Aging, are a practical and engaging way to sharpen your nose and learn to recognize different aromatic nuances. The next time you uncork an aged bottle, take the time to explore its scents and let its bouquet tell its story.