What the Nose Knows: The Science of Scent in Everyday Life (5 page)

S
INCE
THC
ITSELF
is odorless, what gives pot its characteristic aroma? The natural product chemistry of marijuana is complex. Depending on the exact technique used—headspace capture to analyze the scent given off freely by the plant, or steam distillation to extract its essential oils by force—there are anywhere from eighteen to sixty-eight volatile chemicals. Most of these are familiar to plant chemists; they belong to a class of molecules known as terpenes, which occur in the floral scents and essential oils of many species. Examples are beta-myrcene and limonene, which are found in nutmeg, orange oil, and basil, as well as marijuana. Of course, not every volatile chemical has an odor, and even those that do may not be present in sufficient quantity to be detected by the human nose.

To construct the definitive chemical profile for pot aroma, one needs to perform a GC-O analysis. Remarkably, no such analysis has been published, and we don’t know for sure which molecules are critically responsible for its characteristic odor. Sensory analysis by enthusiastic amateurs can be found on the Internet and suggests a winelike variety of nuances. The authoritative-sounding Standard Smoke Report asks aficionados to describe fresh buds and smoke with terms that include ammonia, earthy, licorice, and peach. An evocative, if tongue-in-cheek, review of a Beck concert in Costa Mesa noted several varieties present in the haze above the Pacific Amphitheater: “the gorgeous and unmistakable aromatics of California Indica—a fine blend of orange-flavored Californian strains, sweet acidity and a delicate finish…” Can the average pothead really sniff the diff between California Indica and Super Afghani? I close my eyes and recall Bob Marley, barely visible in a wall-to-wall ganja cloud at the Santa Cruz Civic Center, and Jerry Garcia spotlit in the doobie fog of the Winterland arena. Distinct varietal aromas? Not back then. But the market has evolved. Jim Woodford, the forensic drug sniffer, tells me the East Coast product often smells “like minty oregano,” while the West Coast version is generally “skunky.”

T
HE INDEPENDENT
perfumer Harris Jones once formulated a pot smell for a client who manufactured scented candles. He included beta-pinene and limonene and all the rest, but to achieve a realistic final impression (or, as he puts it, a good “touch”), Jones found he needed a skunky note. He did some research on skunk secretions and concocted his own Pepé Le Pew formula. He prepared a solution of it at .01 percent, and used that at .5 percent in the total formula. The client loved it, but Jones ultimately dropped the project once he realized how many different ways he could be sued should drug dogs and angry parents find his rendition too accurate.

The realism provided by the trace of skunk may explain an anomalous finding in the 1970s by some Canadian psychologists. Exploring aversive odor conditioning as a way to interfere with marijuana intoxication, they put finely chopped strands of human hair into a joint; when lit, it produced a highly unpleasant smell. They gave doctored spliffs to volunteers who were already high from a smoking session in the laboratory. Contrary to expectations, smoking the stinky weed significantly increased the perceived high of the volunteers. Not only did the smell of burning hair fail to kill the buzz, it boosted it.

T
HE SWEET, FUNKY
smell of pot is saturated with social attitude, as is patchouli oil, its counterculture twin, once used by hippies to mask the smell of pot. While patchouli has become a popular fragrance ingredient in consumer products, potlike notes rarely appear in the marketplace. Is it time for marijuana to become a brand-associated scent?

How well do purported pot re-creations measure up? A car air freshener in the shape of a cannabis leaf smells like rancid compost. The Showtime network ran a scented ad in
Rolling Stone
for the 2006 season of
Weeds.
The scent was as cheesy as the “Catch the Buzz” tag line: a blend of lawnmower clippings, potting soil, and cedar shavings (the poor man’s patchouli). Cable industry pundits were coy, calling it “a distinctive herby aroma” evocative of “a certain something.” Then there is
Cannabis Santal Eau de Parfum
from Fresh, a fragrance division of France’s LVMH. “A forbidden blend of patchouli, cannabis and rose, this sensual fragrance captures the raw energy of a man and the desire for him.” I stopped by the ultracool Fresh boutique on Spring Street in lower Manhattan to give it a try. The Fabio lookalike at the counter recited the ingredients with impressive accuracy, but unfortunately he had been trained to spray the wrong end of the perfume blotter. (For future reference, dude, you hold the wide end and spray the narrow end.)
Cannabis Santal
was pleasant, with a nice patchouli note, but it didn’t come within a bong’s length of smelling like real pot. In the end, the most these commercial promotions dare to do is wink at the consumer and say “made ya smell!”

Smellscape in a Bottle

John Muir experienced an olfactory epiphany on the upper reaches of California’s Feather River. For a few minutes the smellscape of the Sierra foothills revealed itself to him in all its swirling splendor.

The air was steaming with fragrance, not rising and wafting past in separate masses, but equally diffused throughout all the wind. Pine woods are at all times fragrant, but most in spring when putting out their tassels, and in warm weather when their gums and balsams are softened by the sun. The wind was now chafing their needles, and the warm rain was steeping them. Monardella grows here in large beds, in sunny openings among the pines; and there is plenty of bog in the dells, and manzanita on the hill-sides; and the rosy fragrant-leaved
chamaebatia
carpets the ground almost everywhere. These with the gums and balsams of the evergreens formed the chief local fragrance-fountains within reach of the wind.

Muir’s image of fragrance fountains is wonderful, yet his dry references to Latin scientific names make us thirst for a more compelling description. Take the large beds of
Monardella
, for example; what does it smell like?
Monardella
belongs to the mint family. Given the locale, Muir was probably describing coyote mint (
M. villosa
) or pennyroyal (
M. odoratissima
). I have hiked through ground covered in California pennyroyal and inhaled the fresh fragrance rising from the bruised leaves beneath my boots. Muir’s description of “rosy fragrant-leaved
Chamaebatia
” leads one to imagine a pleasing floral scent, but this couldn’t be further from the truth.
Chamaebatia
is a member of the rose family, but the plant he smelled (
C. foliolosa
) is unique to California. Its leaves are dull green feathery fronds, sticky with resin, and it sports tiny white flowers. The Miwok Indians called it
kit-kit-dizze
, but the settlers knew it as “Sierra Mountain Misery” or “Bearclover,” names that reflect its pervasive, heavy aroma, akin to cooked artichokes or dilute cat urine. On a hot day in the Sierra Nevada, this musty smell rises like a tide and covers the land all the way from the Feather River where Muir inhaled it, past Lake Tahoe, down to Yosemite and to the southern foothills in Tulare County.

If only Muir’s prose were as aromatic as his visual images. He rouses our curiosity, but can’t sate it. We want to sniff. We want to dip a cup in the showering fragrance fountain. Why can’t someone give us Muir’s afternoon on the Feather River?

F
OR NEARLY ALL
of human history, capturing a scent from nature meant collection and extraction. Heaps of flower petals and baskets of resin were gathered and their essence stripped out with heat or solvents. The result of this harsh processing may be beautiful on its own, but it is a distorted and distant version of the original. The recent quiet revolution in technical chemistry has changed the way we capture scent, in addition to helping us understand its components. By the mid-1970s, GC/MS technique had become so sensitive that the amount of sample required for analysis was 10 to 50 micrograms, an incredibly small quantity. As my former colleague the Swiss fragrance chemist Roman Kaiser describes it, this is “approximately the amount given off by a moderately fragrant flower over the course of one hour.” Kaiser and a few other experts developed nondestructive means of collecting scent. They take it from the air (or “headspace”) surrounding the sample. Whether it’s an orchid on the vine or a fruit on the branch, they don’t physically disturb the odor source; they merely place a glass bulb around it and use an electric pump to suck the headspace through a molecular “trap”—a tube full of porous polymer that absorbs the scent. The trap can be stored and its captured scent later injected into a GC/MS back in the lab.

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.

F
ROM 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 of Virginia or Georgia or Tennessee, or from Texas uplands, or Florida’s glades…

—W
ALT
W
HITMAN,
Leaves of Grass

Pine forest or prairie, seashore or bayou, the essence of the ambience is there for the taking. To carry it away, all you need is a pump and a trap. To reproduce it is not trivial—it’s a matter of money and determination—but it is firmly within our technological grasp. We can re-create the scent of coyote mint and pennyroyal and Sierra Mountain Misery. We can project them into your living room or office cubicle. Imagine them unspooling in slow transitions—a diorama for the nostrils—while you listen to Muir’s afternoon on the Feather River, or to Whitman’s ode to the American outdoors. What would you like to smell? For myself, I’d vote for the sea breeze at Point Reyes and the scent of the redwoods at Big Sur.

I
N HIS 1947 MEMOIR
Speak, Memory
, the novelist and butterfly expert Vladimir Nabokov recounts a moment from one of his summertime collecting trips:

Unmindful of the mosquitoes that coated my forearms and neck, I stooped with a grunt of delight to snuff out the life of some silver-studded lepidopteran throbbing in the folds of my net. Through the smells of the bog, I caught the subtle perfume of butterfly wings on my fingers, a perfume which varies with the species—vanilla, or lemon, or musk, or a musty, sweetish odor difficult to define.

Scented butterflies are not exotic or rare. The Green-veined White, for example, is common throughout Europe and in parts of the United States, where we call it the Mustard White. To the British lepidopterist George Longstaff, its “strong and distinct” odor resembled lemon verbena. Back in 1912, he wrote: “It is curious that to this day so few persons are practically acquainted with the scent of the Green-veined White. When, at the Brussels Conference, in 1910, I caught a male
G. napi
in the beautiful garden of the Congo Museum, and demonstrated the scent to half a dozen entomologists present, none of these gentlemen had perceived the scent before, though at least one of them was a very eminent observer.” The situation hasn’t changed much in the last hundred years. No current field guides mention the scent of the Green-veined White—or of any species, for that matter. The fussy “butterflies through binoculars” crowd discourages physical contact with actual insects, but there are plenty of Mustard Whites in the Rocky Mountains, and you don’t have to be as brutal as Nabokov. Go ahead and catch one for yourself. Sniff and release.