Spectroscopic sensibilities - The Secret of Scent and rediscovering my nose

Writing about smelling things makes me feel remarkably uneasy. It seems to be more acceptable somehow to write about music or noise, photography or fashion, even about its food and drink counterpart than it is about odour itself. But it doesn’t have to be this way. Developing the sense of smell is, after all, a skill, a talent, an art, just like learning to listen and to see. And, standing as I do at the very bottom of the olfactory learning curve, I’m very bad at it.

Unless I had a cold and I couldn’t breathe or taste properly, I took my sense of smell totally for granted. I would pay great heed to it in potentially negative scenarios, like sniffing for food or clothes that were a bit off - until recently, when a book opened my nose to that most chemical of arts, perfume.

That book was The Secret of Scent by Luca Turin. I unexpectedly found this alluring accord of olfactory geekery and scientific erudition on my bookshelf at home, where it had been left by my father who, as a consulting chemist, works with fragrance firms from time to time. His basic book on the science became my gateway to experiencing this sense afresh.

Luca Turin is a biophysicist blessed with an evident passion for perfume and a deft turn of phrase. His effervescent enthusiasm for the art is infectious, and drew me into a mysterious world of chypres, fougères, coumarin, aldehydes and patchouli, into a world of Chanel No. 5 and Poison. These strange and wondrous terms made me realise how sparse my vocabulary is for the nose. Not merely in terms of having heard of the words, but in terms of associating them with a meaning, that meaning being a smell.

Like a conjouror with a red-inlined cape, Dr. Turin suddenly yet elegantly swirls context from the artful to the scientific. He begins by describing each of the key scent types in words and with diagrams of their molecular structures, which play such a key role in the theories of scent. Then he constructs the narrative surrounding their discovery and their relationship with our brains.

How these molecules are translated into scent signals has always been something of a mystery to science, but it was always something of a brackish backwater to science, not appealing to many, being confounded as it was with biology. In the meantime everybody else continued with their business of smelling things and making things smell as nice as possible regardless, just as footballers blithely make use of some of the most complex physics imaginable without them troubling their bank balances or intellects.

The presence of unique molecular receptors in the nose was confirmed in the early 1990s, but how those receptors were activated, in what amounted to a lock and key theory remained unexplained.
Luca Turin’s idea was a synthesis and development of disparate ideas from the past, with a fine story of book shops in Moscow and in Portugal, of fundamental research made at Ford Motor Company, of all places - but in essence, it centres on the idea of the nose being an exquisitely finely tuned spectroscope operating on the principal of molecular resonance. Like odorous instruments, each molecule has its own set of harmonics, which set the timbre of that instrument, of that smell.

The theory still has its opponents and its inherent difficulties in validation - the critical tests still rely on peoples’ noses: according to the theory, two identically shaped but differently massed molecules (e.g. through isotopes) should smell different. Equally, two completely dissimilar molecules with the same frequency spectra should smell the same. The evidence seems to be stacking up in favour of this theory - but its detractors and some counterevidence remain.

But for now I personally don’t really care how the theory is getting along*. I’m too busy rediscovering my nose and the whole sensory apparatus associated with it. I want to try out some of the unique, individual scents in a fragrance. I want to know if I can “imagine” roast chicken in the same way that I can visualise a car or hear music. Can I learn to remember a smell, or a taste? That’s something that I’m remarkably poor at doing.

The main thing is that there’s a part of me that has been active only in the background for so many years - it’s time to give it some room to breathe!

*Neither, apparently, does Dr. Turin.. He does, however, care that his theory is getting results. He founded a company dedicated to designing scents based on their spectral profiles and has had some notable successes, including a replacement for the natural yet carcinogenic coumarin. This company, alongside his books, is how he makes his money...

You can find out more about Luca Turin via his 2005 TED talk and from a BBC Horizon programme from 1995 when the theory was very fresh and very controversial.