Aroma

What is Aroma? Aroma is the bouquet of volatile compounds in wine that we detect through the olfactory system, separate from the five primary tastes registered on the tongue. These airborne molecules carry the personality of a wine, signalling everything from grape variety to winemaking choices and time spent in bottle. Traditionally, sommeliers distinguish aroma in the narrow sense, meaning scents unique to the grape and most evident in young wines, from bouquet, the smells that develop through fermentation and aging. Understanding aroma is the gateway to understanding wine, because the nose tells you far more about a glass than the palate ever can.

The Burgundy Three-Tier Framework

French tasters from Burgundy organise wine aromas into three categories that map cleanly to a wine's life cycle. Primary aromas come from the grape itself: think lychee in Gewurztraminer, grassy notes in Sauvignon Blanc, or floral lift in Riesling and Muscat. Secondary aromas emerge during fermentation, when yeast converts sugar to alcohol and throws off esters and other compounds through acid-alcohol reactions. Tertiary aromas appear later, as the wine matures in oak or in bottle, producing the deeper, more savoury notes associated with age such as honey in older Sauternes.

This framework is useful because it gives a tasting note structure. Once you can place a scent into one of the three tiers, you start to read the wine's history in the glass, separating what the vineyard gave it from what the cellar built on top.

The Chemistry Behind the Glass

Several families of compounds do most of the heavy lifting. Methoxypyrazines produce the green, herbaceous edge of Cabernet Sauvignon and Sauvignon Blanc. Monoterpenes drive the floral, perfumed quality of Gewurztraminer, Muscat, and Riesling. Norisoprenoids contribute spice and fruit, ranging from raspberry to rose oil to vanillin, while thiols and other sulfur-containing mercaptans deliver varietal character that you cannot easily fake.

Much of this complexity is hidden in the young grape. Most aroma compounds are bound to sugars as odourless glycosides and only release through hydrolysis during fermentation and aging. This is why a wine can smell relatively quiet at first and then unfold months or years later in the bottle. Aroma molecules generally sit below a molecular weight of around 310, light enough to evaporate, reach the nose, and bind to roughly six to ten million olfactory neurons spread across about 2.5 square centimetres of tissue.

Smelling a Wine Properly

A few simple habits sharpen what you perceive. Warmer temperatures and a gentle swirl raise the volatility of aroma compounds, pushing more of them into the headspace above the wine where your nose can catch them. Serving a complex red too cold or leaving a glass still in your hand mutes much of what is actually there.

Pacing matters too. The olfactory nerve fatigues after roughly six seconds of continuous smelling, so short sniffs with brief pauses outperform a long, hard inhale. Give the wine a moment in the glass, swirl, sniff briefly, rest, and return. That rhythm is how trained tasters keep reading a wine long after a casual drinker has stopped noticing anything new.