Wine Will Never Smell the Same Again: Luca Turin and the Science of Scent

I’ve recently discovered someone that I think may be perhaps the greatest writer of tasting notes in the history of the English language. He’s not a wine critic, and the notes aren’t about wine. But Luca Turin can write about what he smells better than anyone I have ever seen.

Luca Turin is many things, but perhaps most of all he is a scientist. But then again that may be too small a word for a man whose career has consisted of smashing down many of the walls that divide traditional scientific disciplines. Pioneer might better describe this man who may have finally figured out one of the biggest mysteries of the human body: how it is that we smell things.

Fantastically, Turin embarked on his journey to the theory that may yet win him the Nobel Prize not as a biologist, or a chemist, or a physicist (though he had to become all three along the way) but as a lover of perfume. And not just a lover, but a critic — and not just any critic, but, as it happens, the first real perfume critic. Ever.

Here’s how Turin describes the perfume Nombre Noir, which he credits in his book, the Secret of Scent, as the smell that got him hooked:

The fragrance was, and still is, a radical surprise. A perfume, like the timbre of a voice, can say something quite independent of the words actually spoken. What Nombre Noir said, was ‘flower.’ But the way it said it was an epiphany. The flower at the core of Nombre Noir was halfway between a rose and a violet, but without a trace of the sweetness of either, set instead against an austere, almost saintly background of cigar-box cedar notes. At the same time, it wasn’t dry, and seemed to be glistening with a liquid freshness that made its deep colours glow like a stained glass window. The voice of Nombre Noir was that of a child older than its years, at once fresh, husky, modulated, and faintly capricious. There was a knowing naivety about it which made me think of Colette’s writing style in her Claudine books. It brought to mind a purple ink to write love letters with, and that wonderful French word farouche, which can mean either shy or fierce or a bit of both.

Turin would be a captivating figure solely for the basis of his uncanny, almost preternatural ability to translate between the realm of scent perception and the English language. But his story is much richer than that, and his gifts more prodigious.

With utter disregard for the traditional canons and boundaries of scientific inquiry, Turin found himself on an odyssey that began with that first whiff of Nombre Noir, and ended with an unorthodox, but seemingly sound combination of experimental science that has effectively rewritten the Theory of Smell. And if that weren’t interesting enough, Turin and his theory have met with nothing but fierce opposition and rancorous opprobrium from the scientific establishment.

Luca Turin’s story and the story of how he developed this theory is told in Chandler Burr’s The Emperor of Scent, and Turin’s own The Secret of Scent, which together (to borrow a description provided by a winemaker friend of mine) may well be the most important books about wine in existence that aren’t actually about wine.

When it comes to tasting wines, our tongues and taste buds are merely blunt instruments — the sensorial equivalent of solving a Rubik’s Cube with boxing gloves on. We perceive but 5 tastes — sweet, sour, bitter, salty, and umami (which many people describe as “savory”). And together these taste buds could never give us the gunflint and lime zest of Sancerre or the graphite, tobacco and cherry of Bordeaux. No, for all the delicious sensations of the wine world, we need our sense of smell.

For decades, and even today, in many hallowed institutions, the accepted explanation of how smell works can be described in a single word: shape. It goes something like this: all molecules are shaped differently and we have receptors in our noses that match all the different molecules out there in the world that we can smell. A molecule floats into the nose, somehow finds its way to an appropriate receptor and like two jigsaw puzzle pieces fitting together, violá, we smell the rose.

Except there are all sorts of reasons why that is pretty much impossible. I can’t do justice to the scientific explanations of this, but for starters, we’ve actually figured out where the smell receptors are, and counted them and there are 347 of them. But we have not yet discovered a limit to the number of molecules that we can smell, and we’re inventing new smells all the time, meaning that there cannot be a one-to-one mapping of molecule to receptor. Which pushes the traditional theory to a place where instead of gripping the whole molecule, our receptors grip only a part of it and read it like Braille. The problem with this approach is that there are many molecules with very similar shapes that smell entirely different, as well as molecules with vastly different shapes that smell quite the same. All of which means that it’s pretty much impossible to predict what any given molecule will smell like.

And of course, that’s what any good scientific theory should let you do: set up a situation and predict the result. And when it comes to the shape theory of smell, there isn’t anyone who can look at the shape of a molecule and predict how it will smell to us. Which is why perfume companies spend hundreds of millions of dollars creating thousands and thousands of molecules hoping that one of them will smell like what they secret_scent_cover.jpgwant.

Neither the theory, nor the “machine gun” approach to scent chemistry made any sense to Turin, and so he decided to figure out how our noses really work. It took him years, and some chance discoveries of long-forgotten scientific research by others who were on the same quest, but eventually he did it. And the answer to the question of how our sense of smell really works is nothing short of remarkable.

The answer, Turin says, is that the receptors don’t “feel” the molecules at all. Instead they listen to them like the plucked string of an instrument.

Every molecule vibrates at its own specific series of frequencies that are determined by its chemical makeup. Smack that molecule with some energy (say, a photon or electron) and it will hum its particular chord of vibrations that can be easily measured. This fact produced the invention of the spectrograph, a very handy tool we humans have used to analyze the chemical content of pretty much everything in the universe.

And, it turns out, that’s exactly what we have in our noses. Little mini spectrographs that smack scent molecules around with electrons and measure the frequencies so that we can send signals to our brains that say “mint” or “manure.”

Burr’s chronicle of how Turin came to his amazing conclusion made for one of the most fascinating non-fiction books I have read in a long time. The story is made even more fascinating by the petty politics and obdurate close-mindedness of the scientific world that have prevented Turin’s theory from completely overturning the prevailing theory, as all good scientific advances are supposed to do.

Turin’s own book leaves out the petty politics almost entirely, and goes deeper into the leaps of insight and logic that led him to his remarkable conclusions.

The combination of the two books have completely changed the way I think about aromas, and deepened my appreciation for the magical flavors of wine. I highly recommend them to anyone.

Luca Turin was kind enough to respond to an e-mail I sent him some time ago, and answered (albeit briefly) a bunch of my layman’s questions.

AY: We all hear and learn in school that we have 5 primary taste receptors — salty, sweet, bitter, sour, and umami — and that most of what we actually perceive as the flavor of what we drink is actually aroma. Is this true, and can you describe the mechanism by which we “smell” the stuff that’s in our mouths?

Turin: The olfactory epithelium sits a the top of the nasal cavity which is open both front (nostrils) and back (above the soft palate). What’s in your mouth reaches it from the back before and during swallowing.

AY: Do you know how our sense of something’s flavor is constructed in our brains as a result of the aromatic components and the sensory input to the taste buds? I’m curious about the interplay between olfaction and tasting…

Turin: Not sure, but the fact that wine is indistinguishable from swill when you have a severe cold suggests that the mouthfeel and taste input is small.

AY: The number of molecules needed for us to actually smell something, like a note in a perfume is amazingly small [Turin did a scent demonstration at TED, which involved about 400 molecules, he said]. Do you know if the same is true for the aromatic parts of flavors?

Turin: Different materials (molecules) differ by several orders of magnitude in potency, ranging from linear alkanes (quite weak) to sulfides (very strong)

AY: There’s a line in your TED talk where you say “Do not think that this is subjective. You are all smelling pretty much the same thing” and you go on to explain that that our perception of aromas is largely the same from person to person, which is why there is a perfume industry. Can you explain more about this? And do you think the same is true of our perception of flavors?

Turin: Much has been made of the supposed subjectivity of odor, whatever that means. For some reason people seem to think that “apple” is a less solid descriptor than “blue” or “oboe”. I know only of one or two cases where different people smell a molecule completely differently, as in woody vs. urinous. In all others, they pretty much agree. The constancy of color, sound and odor is what enables an artist to make something that will be generally appreciated.

AY: Is there a limit to the number of things that we can smell as humans? In the same way that we can only see certain wavelengths of light? Do we know what the limits are? How would you describe them?

Turin: We use three different color receptors rather broadly tuned within a range spanning about one octave of electromagnetic vibration to distinguish thousands of colors. Presentation of color is easier than presentation of odors, and the limits and resolution of color space are known accurately for stimuli on a dark background. The situation is immensely more complex for reflected-light multicolor scenes, for which the algorithm that the brain uses to calculate color is still in part mysterious, despite the pioneering work of E H Land of Polaroid fame. In the case of odor, the limits are not known: no two different molecules have ever been found to have identical odors.

AY: These days, a lot of people are talking about supertasters — people with a higher concentration of taste buds on their tongues than normal. Are you familiar with this concept? Is there any analogue in the world of smell?

Turin: There may be, but I’m not aware of it. Pregnant women are frequently hyperosmic.

AY: Where does the biophysics of smell — the sensation — transition to the perception and the recognition of aromas? What does modern science know about the relationship between these two?

Turin: Modern science knows rather little about this, and much of what is known seems to be common sense translated into jargon.

AY: What do you personally smell when you taste wine? Do you find yourself smelling different things than others because of your training?

Turin: No, though sometimes hilarious associations with fragrance do come to mind. I like huge, dark, smoky reds and shy away from any kind of refinement.

AY: What’s the most interesting or oddest thing you’ve ever smelled in a wine?

Turin: The plucked chicken skin note of certain sweet Loire whites.

AY: Do you have a favorite wine or a favorite moment related to wine?

Turin: When I first tasted a recent vintage of Feudi di San Gregorio’s Serpico, I thought my ship had come in. Unfortunately I can’t afford the passage. I also remember a ’76 Rieussec as insanely great, and even more expensive. I think Concha y Toro is the world’s greatest firm after Apple, Inc.

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And just to close, let me offer you Turin’s thoughts on a 1959 Chateau Rieussec Sauternes, as captured by Chandler Burr:

Utterly sensational. Fresh as a trout. Sauternes are very saturnine, a honeyed summery exterior covering a late November liquid. There are three elements — a beeswax, a woody, and a floral banana — with a perfect balance between extreme acidity and huge, heavy, oily sweetness, like a blend of jasmine and musk. A great Sauternes is a perfectly proportioned thing. Rieussec makes big-boned, stocky affairs. The ’59, in a bottle for forty years, comes out the way James Bond emerges from a wet suit in a perfect tuxedo. It looks at you and murmurs, ‘What kept you?”

I can’t help myself. I love this guy.

Chandler Burr, The Emperor of Scent: A True Story of Perfume and Obsession , Random House Trade Paperbacks, 2004, $10.17

Luca Turin, The Secret of Scent: Adventures in Perfume and the Science of Smell, Harper Perennial 2007, $12.55 (softcover)