The three layers of wine aroma

Primary aromas

Aromas derived directly from the grape variety — fruit, floral and herbal notes. Not technically "bouquet." Examples: the blackcurrant of Cabernet Sauvignon, the lychee of Gewurztraminer, the gooseberry of Sauvignon Blanc.

Secondary aromas (fermentation bouquet)

Aromas created during fermentation by yeasts and bacteria. Includes buttery notes from malolactic fermentation (diacetyl), bread and biscuit from autolysis in sparkling wine, and yeasty, creamy characters in many whites.

Tertiary aromas (aged bouquet)

Aromas that develop through oxidative ageing in barrel and/or reductive ageing in bottle. This is what most people mean by "bouquet." Examples: dried fruit, leather, tobacco, mushroom, truffles, coffee, chocolate, dried herbs, petrol (in aged Riesling), earthy forest floor.

Oak-derived aromas

Vanilla, coconut, toast, smoke, cedar, spice — contributed by oak barrels during ageing. Technically secondary, but often described alongside the bouquet. French oak gives finer, spicy notes; American oak gives bolder vanilla and coconut.

How bouquet develops with age

As a wine ages in bottle, the primary fruit aromas gradually transform through a series of complex chemical reactions. Esters (responsible for fruity aromas) hydrolyse slowly, reducing fresh-fruit intensity. At the same time, new compounds form through oxidation, reduction and the interaction of acids, alcohols and phenols. Terpenes — responsible for floral and citrus notes in some varieties — rearrange into new configurations. The characteristic petrol note in aged Riesling, for example, comes from the formation of TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) over years in bottle. This is why old Riesling smells nothing like young Riesling. For how tannin interacts with these ageing processes, see the glossary entry.

Bouquet versus faults

Genuine aged bouquet must be distinguished from wine faults that can produce superficially similar characteristics. Excessive oxidation produces flat, vinegary, sherry-like notes — not the same as the controlled, complex oxidative notes of a great aged Burgundy. Cork taint (TCA) produces a damp cardboard, musty smell that suppresses all positive aroma. Reduction produces sulphur-related off-notes (struck match, rubber, drains). The key test: does the nose show complexity and harmony, or is there a single dominant unpleasant note? A wine with a developed bouquet has a full, layered aromatic profile; a faulty wine is typically dominated by one off-note with diminished fruit behind it.

Sources: WSET (systematic approach to tasting, Level 3 and 4), Jancis Robinson MW — Oxford Companion to Wine (aroma entry), AWRI (wine aroma chemistry), OIV (oenological terminology). Corrections via the contact form.