Why Does Wine Taste of Things That Aren't in It?
Andi Healey
Web Manager
The Riedel Shop · Wine, Without the Waffle
TL;DR
Nobody adds blackcurrants to a fermentation tank. Wine contains real aroma compounds, some of them identical or closely related to the ones responsible for smells like green pepper, black pepper or petrol, but your brain does the last, crucial step of matching that chemical signal to a word. That's why tasting notes can be chemical, personal, and occasionally ridiculous, all at once.
Blackcurrant. Raspberry. Violet. Tobacco. Leather. Pencil shavings. Wet stones. Petrol. Cat's pee.
Read enough tasting notes and you start to wonder what exactly is going on in the winery.
Nobody is stirring a handful of pencil shavings into the tank. Nobody has a violet on standby. And yet these words turn up again and again, written by people who are not, as far as anyone can tell, either making it up, or completely bonkers.
So what does it actually mean when someone tells you a wine "tastes of blackcurrant"?
Not as much as you'd think, and also considerably more than you'd think, depending on which part of the sentence you're focused on.
Working that out is a decent way of understanding what's actually happening every time you put a glass to your lips.
Taste isn't doing all the work
Let's start with the tongue, because that's where most people assume the detective work happens.
Your tongue can detect five things: sweet, sour, salty, bitter and umami.
That's it.
Everything else you associate with a wine's flavour, the fruit, the herbs, the leather, the pencil shavings, isn't taste at all. It's aroma, and most of it is picked up by your nose.
That includes the aroma you notice while the wine is actually in your mouth. When you swallow, or even just breathe out with wine still on your palate, air carries aroma compounds up through the back of your throat to the same olfactory receptors that detect smell through your nostrils. This is called retronasal olfaction, and it's doing far more of the work than your tongue ever will. It's why food tastes of almost nothing when you have a blocked nose: the taste buds are all present and correct, but the aroma channel that supplies most of the detail has been switched off.
So when a wine "tastes of" blackcurrant, what's really happening is that your nose, not your tongue, has picked up a smell it recognises. Your tongue is confirming the sweetness, the acidity, the bitterness of the tannin. Everything more specific than that is smell masquerading as taste.
Wine does contain those molecules
Here's the part that stops this being a purely psychological trick. Wine contains hundreds of volatile aroma compounds, and a fair number of them are chemically identical, or very closely related, to the compounds responsible for the smells they're compared to.
Take green pepper. Cabernet Sauvignon, Cabernet Franc and Sauvignon Blanc can all carry a distinct green pepper note, and the compound behind it, 3-isobutyl-2-methoxypyrazine (IBMP for short), is present in incredibly small amounts. Your nose can detect it at concentrations of just a few nanograms per litre, one of the lowest perception thresholds of any aroma compound in wine.
A tiny amount goes a long way. IBMP is also responsible for "cat's pee on a gooseberry bush"*, one of the most unappetising tasting notes I've ever come across.
Or take black pepper. Some Syrah, Shiraz and Grüner Veltliner carry genuinely peppery, spicy aromas, and the compound responsible, rotundone, is the same one actually found in black peppercorns.
It's not close, it's not similar to. The wine contains a compound that is, molecule for molecule, doing the same job in your nose that ground pepper does.
None of this means the wine literally contains green peppers or peppercorns. It means the wine contains a compound that your olfactory receptors interpret the same way, because it's either the same molecule or one close enough that your nose can't tell the difference. The tasting note isn't inventing anything. It's naming the closest real-world match to a genuine chemical signal.
Your brain does the rest
Here's where it gets really interesting. Detecting a compound is only the first half of the job. Your nose sends a chemical signal; your brain has to decide what that signal means, and that decision is built almost entirely from memory.
Smell, more than any other sense, is wired directly into the parts of the brain that handle memory and association. When an aroma compound hits your olfactory receptors, your brain isn't running a chemical analysis. It's asking a much simpler question: what does this remind me of?
That's why two people can smell exactly the same wine and describe it completely differently. Someone who has spent years professionally tasting wine might reach for "blackcurrant leaf" specifically, because they've built up a detailed, well-labelled library of smell memories to draw on. Someone else might just say "fruity", not because their nose is worse, but because their internal library has fewer reference points. Neither is wrong. They're both reporting an honest match against their own memory.
Why wine writers say "notes of…"
This is why "notes of" is a more honest phrase than it sometimes gets credit for. It isn't a wine writer claiming the winemaker snuck blackcurrants into the fermentation. It's shorthand for something close to: "the aroma compounds in this wine are triggering the same recognition response in my brain as blackcurrants do."
Once you read it that way, tasting notes stop being a slightly absurd shopping list and start being useful. Someone has taken a chemical and sensory experience and converted it into language you can compare against your own memory. It won't be an exact match, because your smell library isn't identical to theirs, but it gives you somewhere to start.
It's also why, when you are tasting wine with somebody else and they say "lychee", for instance, your brain goes "oh, of course, lychee!"
Why some people smell things you absolutely cannot
Two things explain why tasting notes can feel like they're describing a different wine entirely: genetics and memory.
Genetics first. Sensitivity to specific aroma compounds varies enormously between individuals, and it isn't a small effect. The clearest example is cork taint. The compound responsible, TCA, can be detected by sensitive individuals at concentrations below one part per trillion, while others need roughly two hundred times that concentration before they notice anything at all. Rotundone, the black pepper compound I mentioned above, is similar: research has found that around 40% of people are effectively unable to smell it at any concentration tested, while the rest vary widely in how much they need before it registers. This isn't a question of expertise or effort. It's down to which olfactory receptors you were born with and how many of each type you have.
Then there's memory, which is arguably the bigger factor. A tasting note is only useful to you if the reference point means something. If you've never smelled a fresh rose, "rose" is a word, not a sensation, and it won't help you identify anything in the glass. Your own life supplies the library your brain checks against, which is why the same wine can generate wildly different, equally sincere descriptions from different people in the same room.
And then there's petrol
No article on this subject is complete without Riesling's petrol note, because it's the cleanest possible illustration of the whole thing.
Aged Riesling, particularly from warm vintages, can develop a distinct kerosene or petrol character. The compound responsible is TDN (1,1,6-trimethyl-1,2-dihydronaphthalene), and, although it is present in young wine, it's not in any meaningful amount. It forms gradually as the wine ages, through the breakdown of compounds already present in the grapes, a process that starts with sun exposure in the vineyard, and increases over time. A young Riesling might contain barely any; a well-aged bottle can carry levels well above what most people can detect.
There is, it should go without saying, no petrol in your Riesling. There has never been any petrol anywhere near your Riesling. What's there is a compound your brain files under "petrol" because that's the strongest reference point most people have for that particular smell. It's a slightly unfortunate association for the wine, and a very useful one for anyone trying to understand how tasting notes actually work.
Does wine actually taste of anything, then?
Yes, of course. But describing a wine isn't the same exercise as listing its ingredients.
A tasting note is an attempt to translate a chemical and sensory experience into language other people can compare against their own memories. That translation is built on real chemistry: the compounds are genuinely there, and in a good number of cases they're the same compounds, or close relatives, of the things they're being compared to. But the final step, turning a detected molecule into a specific word, happens in a brain shaped by genetics, training and personal history. That's why tasting notes are useful, subjective, learned and, every so often, faintly ridiculous, all at the same time.
The next time somebody tells you their wine smells of blackberry, tobacco and pencil lead, they're telling you what the wine reminds their brain of, based on a genuine chemical signal and a lifetime of their own smell memories.
Once you understand that, tasting notes become considerably less mysterious, and perhaps a little less intimidating.
Although I remain unconvinced that anyone has ever genuinely smelled "cat's pee on a gooseberry bush"*, either in real life or in their wine glass.
* "Cat's pee on a gooseberry bush" is a famous, traditional tasting descriptor used by wine critics to describe the pungent, herbaceous, and intensely fruity aroma of certain Sauvignon Blanc wines, especially those from New Zealand. Coopers Creek famously released a commercial Sauvignon Blanc literally labelled "Cat's Pee on a Gooseberry Bush" in 2005 (sometimes spelled Cat's Phee in certain markets for legal or quirky reasons). It became a piece of classic wine humor and a surprisingly strong seller.
FAQs
Does wine actually contain the fruits and flavours mentioned in tasting notes?
Not literally. Wine contains hundreds of aroma compounds, and some are the same or very closely related to the compounds found in the fruits, herbs and other things they're compared to. A wine "tasting of" black pepper contains rotundone, the same compound found in actual peppercorns. What it doesn't contain is the fruit or object itself.
Why do different people get different tasting notes from the same wine?
Two reasons: genetics and memory. People vary enormously in their sensitivity to specific aroma compounds, and a tasting note is only useful if you have a personal reference point for the smell being described. Someone who has never smelled a fresh rose won't get much from "rose" as a descriptor, however accurate it is.
Is cork taint (TCA) detected the same way by everyone?
No. Individual sensitivity to TCA, the compound behind cork taint, varies hugely. The most sensitive people can detect it at concentrations below one part per trillion, while others need roughly 200 times that amount before they notice anything at all.
Why does Riesling sometimes smell of petrol?
Aged Riesling can develop a compound called TDN, which produces a kerosene or petrol-like aroma. It forms as the wine ages, from the breakdown of carotenoid compounds already present in the grape, a process sped up by warmth and sun exposure. There is no actual petrol involved at any point.
Can you train yourself to pick up more aromas in wine?
Largely, yes. Because so much of tasting relies on matching a smell to a memory, deliberately smelling and naming reference aromas (fresh blackcurrant, rose, wet stone, black pepper) builds a bigger library for your brain to draw on. Genetics sets a ceiling for some compounds, but for most people, practice sharpens the vocabulary rather than the nose itself.
Sources consulted for fact-checking:
- Petrol Note in Riesling – TDN Selectively Activates Human Odorant Receptor OR8H1, J. Agric. Food Chem.
- TDN, (1,1,6-trimethyl-1,2-dihydronapthalene) – UC Davis Waterhouse Lab
- Individual Differences in Thresholds and Consumer Preferences for Rotundone Added to Red Wine, Nutrients (MDPI)
- May peppery wines be the spice of life? A review of research on the ‘pepper’ aroma and the sesquiterpenoid rotundone, OENO One
- Everything You Ever Wanted to Know About Cork Taint, Wine Enthusiast
- Organoleptic Impact of 2-Methoxy-3-isobutylpyrazine on Red Bordeaux and Loire Wines, J. Agric. Food Chem.
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