Exploring Wine’s Aromatic Compounds: A Guide to Identifying Key Aromas

Wine’s aromas come from tiny molecules that easily float up from the glass and into your nose. These are called volatile aroma compounds—“volatile” simply means they evaporate quickly.

Even though they exist in incredibly small amounts (sometimes just nanograms per litre), they pack a big punch. Some compounds only need the tiniest concentration for our noses to detect them, while others must be present in much larger amounts before we notice them.

Key Families of Wine Aromas

While there are hundreds of compounds at play, most fall into a few main groups that shape a wine’s personality.

Esters

These are the stars of young wines, giving fruity and floral notes. They’re created during fermentation and can smell like banana, pineapple, pear drops, or even candy. They’re delicate though, so they fade as the wine ages.

Alcohols

Beyond ethanol (the alcohol we drink), wines contain other higher alcohols. These contribute background aromas and can subtly affect texture and mouthfeel.

Acids

Acids not only give wine its zing and freshness, but some of their by-products also influence aroma.

Thiols

Tiny but mighty, thiols are especially important in wines like Sauvignon Blanc. They’re responsible for those tropical notes like passionfruit and grapefruit.

Each of these compounds interacts with others, layering complexity and making wine such a fascinating sensory experience.

Why Some Compounds Matter More Than Others

Here’s an interesting twist: not every compound contributes equally to a wine’s aroma. It depends on how strong the smell is compared to the level in the wine.

Scientists talk about something called the odour threshold. Basically, the lowest concentration at which humans can actually detect a smell. If a compound’s concentration in the wine is above that threshold, we’ll notice it. If it’s below, it usually goes undetected.

This is why a single thiol in Sauvignon Blanc can shape its entire character, even in vanishingly small amounts, while other compounds need to be present in much larger doses before we can potentially register.

It’s not just grapes and fermentation that matter, winemakers also have a huge influence over a wine’s final aromatic profile. Two techniques are especially important:

1. Ageing on Lees

Lees are the dead yeast cells left behind after fermentation. Some winemakers keep wines in contact with these lees to add texture and complexity. Over time, lees release compounds that smell like bread, brioche, nuts, or even creaminess. This is why Champagne and some Chardonnays can smell toasty or buttery.

2. Oak Ageing

Barrels don’t just store wine, they can add flavour to it. New oak contributes vanilla, coconut, spice, and toast aromas, thanks to compounds like vanillin and lactones. The size of the barrel, how toasted it is, and whether it’s French or American oak all affect the final aroma.

Oak can also soften fruitiness, blending it with richer, spicier notes. Through lees ageing and oak use, winemakers can turn the same grape into wines that smell completely different: fresh and fruity, or complex and nutty.

Wine is alive, and its aromas evolve over time. The same bottle can smell vibrant and fruity when young, then develop layers of complexity with age. Here’s how ageing typically plays out:

White Wines

• Young: Dominated by esters → fresh fruit, citrus, floral notes.
• With Age, Fruit aromas fade, replaced by honey, nuts, toast, and petrol (in Riesling). Oak-aged whites may show vanilla or hazelnut.

Red Wines

• Young: Bursting with primary fruit aromas (berries, cherries, plums).
• With Age: Fruit becomes less pronounced, giving way to earthy, spicy, leathery, and dried fruit notes. Secondary aromas from oak (vanilla, spice) blend with tertiary aromas like tobacco or truffle.

Sparkling Wines

• Young: Fresh citrus, green apple, and floral esters dominate.
• With Age (on lees): Develop richer notes of brioche, biscuit, almond, and honey. The longer the wine rests on lees, the more these bakery-like aromas shine.

Read more on how the timing of disgorgement shapes the flavours and aromas of Champagne here

Winemakers have long relied on their senses to describe wines, but modern tools now give us an exact chemical picture of what’s in the glass.

The main method used is gas chromatography–mass spectrometry (GC-MS). Without diving too deep into the tech, it’s basically a way to separate and identify every aroma molecule, even at ultra-tiny concentrations.

These tools let researchers connect the dots between what’s in the wine and what we actually smell. It also helps winemakers tweak their processes, like adjusting fermentation or grape exposure to sunlight, in order to highlight desired aromas.

Visualising Aroma: From Heatmaps to Networks

Because there are so many compounds, scientists often use visual tools to make sense of the data.

• Heatmaps – These show which compounds are present at higher or lower levels in a wine, using colours to highlight the differences.
• Clustering analysis – This groups wines by similarities in their aroma profiles. For example, white wines like Sauvignon Blanc cluster together, while reds like Touriga Nacional form another group.
• Aroma networks – This is a cool newer method where compounds are linked to the aromas they create. Imagine a map connecting “tropical fruit” to thiols, or “berry fruit” to esters. It makes the invisible connections between chemistry and sensory experience easier to see.

Let’s take a couple of examples:

• Sauvignon Blanc – Famous for its vibrant tropical fruit and grassy notes. Chemically, this is thanks to a combination of esters (fruity) and thiols (passionfruit, grapefruit).
• Touriga Nacional (a Portuguese red) – Known for deep berry fruit, violet, and sometimes even roasted meat aromas. This richness comes from higher levels of esters and compounds like β-damascenone.

So when you smell blueberries in your glass, it’s not just poetic, it’s chemistry at work!

Understanding wine’s aromatic compounds doesn’t take away from the romance of wine, it actually adds to it. Knowing that over a thousand tiny molecules combine to create the smell of cherries, vanilla, or honeysuckle makes each glass even more fascinating.

Plus, this knowledge helps explain why wines taste so different depending on grape variety, region, and winemaking style. Science doesn’t strip away the magic but helps to enhance our appreciation of it.

Conclusion

Wine aromas are the result of an incredible interplay between chemistry and our senses. From fruity esters to tropical thiols, from delicate acids to powerful alcohols, every compound contributes to the story in your glass.

Modern science, using tools like GC-MS and aroma networks, helps us understand why wines smell the way they do—but for us as wine lovers, it all comes down to the pleasure of sniffing, swirling, and sipping.

Next time you lift a glass, take a moment to notice the layers of aroma. Behind that bouquet lies not just the work of the winemaker, but also the fascinating dance of hundreds of invisible compounds.