What the Nose Knows - Avery Gilbert [18]
Headspace capture lets us analyze smells as they are produced in nature and as they are perceived by their intended audience (usually bees, bats, and butterflies). By analyzing the composition of a flower’s living scent, rather than the oils extracted from its crushed petals, perfumers can better mimic the real thing back in the studio. The rarest specimens, unavailable in sufficient quantities for traditional extraction, can now be studied. (Having pioneering headspace analysis, Kaiser now uses it to study and preserve the scent of rainforest species threatened with extinction.) Other possibilities abound: the scent of a ripening strawberry can be traced as it changes hour by hour, as can the fragrance of a night-blooming desert flower as it varies from dusk to dawn.
I decided to enlist Roman Kaiser’s help in tracking down the smelly essence of Sierra Mountain Misery. At the end of a camping trip in July 2006, I collected a few sprigs of it on the roadside a few miles west of Sonora Pass. I zipped it into a sandwich bag and stashed it in the beer cooler to keep it fresh as I drove down to Berkeley. I made it to Kinko’s just before the express shipping deadline. Waiting in line, I spotted a sign listing restrictions on international shipments; among the forbidden items was plant material. Damn it. How would I get this stuff to Roman while it was still fresh? I stepped up to the counter, placed my bag of suspicious, leafy green plant material on it, and took a deep breath. “I’d like to send this express to Switzerland.” “And what is it you’re shipping?” asked the clerk. I flushed. “It’s a…scientific sample.” The manager looked over the top of his glasses; was he giving me the hairy eyeball? “Well, then, you’ll need to fill out this international label.” Phew. Good old Berkeley.
Three days later the Mountain Misery was stinking up Roman’s lab in Dübendorf, a village outside of Zürich. Working his usual magic on the GC, he soon extracted around four dozen molecules: a smelly stew of terpenes such as alpha-pinene, beta-pinene, and plenty more. Most of them he could find in his extensive database of fragrant molecules; a few others would need months of work to identify fully with mass spectroscopy. Happily, this wasn’t necessary to pin down the source of the distinctive smell; none of the mystery molecules smelled like Mountain Misery. Remarkably, one molecule, present in only trace amounts (.01 percent), was responsible for 95 percent or more of the cooked-artichoke smell. The chemical at the heart of John Muir’s Sierra smellscape turns out to be 1-hexen-3-one.
Hexenone has been fingered as a key aroma in aged milk, cream, and butter; it also has a starring role in linden honey and fresh raspberries. This illustrates that a complex stew of volatile molecules can smell a lot simpler than what is implied by its lengthy ingredient list; one chemical can dominate an entire bouquet. Another lesson: abundance is not a reliable clue to odor impact; in this case, a single molecule from a single plant provides the aromatic background for an entire ecosystem And finally, it shows that a talented fragrance chemist can find the single molecule responsible for John Muir’s poetic impressions of the Sierra Nevada foothills.
FROM THE WHISPERED fragrance of a single exotic blossom, it is but a step to capturing an entire smellscape. No one had a surer grasp of the grand scale of the American smellscape than Walt Whitman.
The conceits of the poets of other lands I’d bring thee not,
Nor the compliments that have served their turn so long,
Nor rhyme, nor the classics, nor perfume of foreign court or indoor library;
But an odor I’d bring as from forests of pine in Maine, or breath of an Illinois prairie,
With open airs