This unique diversity of grape varieties offers an inexhaustible potential in terms of sensory experience. The wines of the Soutwest possess subtle and varied aromas ranging from violet to truffle, pepper or grapefruit. Thanks to research carried out by the Southwest pole of the French Institute of Vine and Wine, these aromas are increasingly deciphered. Winemakers in the Southwest can now use this knowledge in their vineyards and wine cellars to optimize the exceptional bouquet of our native varieties.
The characteristic grapefruit aromas, always found in Colombard white wines (Côtes de Gascogne IGP), are due to a sulphur molecule called 3-mercaptoxanol. This very fragrant compound, present in the skin of the grapes in the form of precursors, is released during the fermentation process, activated by yeast. This molecule also frequently contributes to the aromas of the rosé wines made with Négrette (Fronton AOC) and Malbec (Côtes-du-Lot IGP) grape varieties and sometimes those of white wines elaborated with Gros Manseng (Côtes-de-Gascogne IGP).
The compound responsible for the bell pepper aromas in the red wines of Cabernet Franc from the Pyrenean foothills, of Fer Servavdou (Gaillac and Marciallac AOC) but also of Cabernet Sauvignon, the king grape variety of Bordeaux, bears the barbaric name of 3-isobutyl-2-methoxypyrazine. This molecule is found in large quantities, especially in cool and rainy vintages. When heat and sunshine are present, the wines’ bouquet evolves towards notes of blackcurrant buds.
With aging, sweet or syrupy wines elaborated with Petit and Gros Manseng (Côtes de Gascogne IGP, Jurançon AOC and Pacherenc du- Vic-Bilh AOC) grape varieties as well as red wines made with Malbec (Cahors AOC) can develop distinctive truffle aromas. They are due to a sulfur molecule called dimethyl sulfide also found in cooked meat, cheese, citrus fruits and some vegetables. It also contributes, when present in small quantities, to the fruitiness of wines.
Rotundone is the molecule responsible for black pepper aromas easily identifiable in the red wines elaborated with Duras, Prunlard (Gaillac AOC) and sometimes Négrette (Fronton AOC) grape varieties. It was discovered in 2008 by an Australian research team. 20% of tasters are unable to smell it, which gives a radically different sensory experience to a given wine! Cool and rainy vintages are particularly favorable to its accumulation in grapes.
The violet aromas typical of the red wines elaborated with the Négrette grape variety (Fronton AOC) are caused by beta-ionone. This molecule is probably produced from beta-carotene, an orange pigment that gives the carrot its color and is sometimes incorporated in sunscreen creams as a filtering agent. Due to genetic changes in sensory receptors, some people are unable to smell this compound. By removing the leaves and exposing the bunches to the sun’s rays, winemakers encourage its accumulation in the grapes.
The “coconut” notes in wines are associated with maturation or ageing in barrels. The molecules responsible are two whiskylactones that are mainly found in barrels made with mildly heated oak staves. These aromas can be found in most of the wines made to be kept elaborated in the Southwest of France, especially those of Malbec and Tannat grape varieties (Cahors, Madiran and Saint Mont AOCs) which are particularly rich in polyphenols and suitable for ageing.
Isoamyl acetate is the main molecule associated with banana aromas in wines. Its presence is often associated with the use of specifically selected yeasts. If this type of micro-organism has a definite impact on this aromatic family, it is above all the conditions under which fermentation is carried out (temperature and juice limpidity) that determine the final aromas found in wine. This compound participates in the bouquet of red primeur wines (Gaillac AOC, Côte-du-Lot IGP) and most white and rosé wines from the Southwest.