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How does our olfactory system work? First, there must be a source, say, an apple pie baking. The pie emits volatile scent molecules. We pick them up via receptors in our noses. About 50 million receptors crowd onto 2.5 square centimeters of the mucus-coated olfactory epithelium in each nostril. (Animal abilities to smell are astounding: the dog's olfactory epithelium, for instance, is 40 times larger than ours.) From the epithelium, electric signals travel to the olfactory bulb, which, like a relay station, disperses the signals to different brain regions. One region is the limbic system, the Grand Central Station of emotion and motivation, where emotions attach to smells. Say you smelled apple pie baking at your grandmother's when you were three. Today when you smell an apple pie baking, you might be transported to her kitchen. You may even associate the smell with your grandmother herself, a childhood memory of security and love, spiced by a single odor.

The science of smell is far more developed than the language we use to describe smells. Consider how many words there are for crayon colors but how difficult it is to name odors. Smell shelves a meager stock of nouns: odor, scent, aroma, fragrance, perfume, bouquet, stench, stink, fetor; and a few general adjectives: redolent, pungent, acrid, aromatic, perfumed, cloying, stinking, musty, frowzy, fruity, rancid, putrid, rank, foul, reeking, sweet, noisome. Since we have few precise descriptors for all 10,000 smells, we often identify them by origin. Hence, on a golf course we say, that's the smell of new-mown grass, or at an Arco station, that's the smell of gasoline. My elderly neighbor was a smoker and a widower who cooked for himself. Entering his home, I was repulsed by the smell -- fried chicken and cigarettes. No precise word for that caustic mix exists. Yet when I state the combination and you imagine a closed-up house, holding grease and Marlboros for years, everyone knows it's a stench.

Moreover, language gets closer to meaning via connotation. In our smell words, we note how some of them buddy up to taste -- fruity, rancid, sweet. Also, a metaphor can be animated by smell, I smell a rat, as can other figures of speech, such as He stank to high heaven. Or how about Juliet's calling Romeo's name from the balcony: What's in a name? That which we call a rose/ By any other name would smell as sweet. Language's adaptability to the figurative shows that the olfactory glossary is not impoverished.

One of the most powerful aromas comes from freshly ground coffee. Almost nothing negative arises with this smell. I think of a brew as early independence, when at college I discovered a coffeehouse with live folk music and poetry readings and I felt centered, free, myself. Lots of workers get a sharpened focus from their midafternoon java: Hey, this job's not so bad after all. There's the solitude and unhurriedness that a good book and a cup of coffee bring. We don't linger with food in our culture -- we stuff it in -- but we like to sip and nurse, smell our coffee mugs.

On the coffee farms of the world's temperate climates, the coffee bean is picked as a red berry, whose skin, after drying, falls away and exposes a green bean. Before they're bought, these beans go through a smelling-and-tasting process called "cupping." To learn how the nose is used in cupping and roasting coffee, I look up a buyer and a roaster at Caffé Calabria in North Park. Michelle Greisgraber is typical of most smell employees: she had no talent per se with nose or tongue (the two are linked in coffee sampling) that led her to this profession; rather, her skill was acquired through a demanding schedule -- two years as a coffee sampler who taste- and smell-tested eight hours a day.

Greisgraber, wide-eyed from daily cupping, is an attractive young woman who likes to pull, twist, and drape her long straight hair over her right shoulder. Before she buys any coffee, she tests, or cups, a sample: she's looking for defects that the green bean may have contracted between the time it was harvested and the time it arrived in the café. For example, she says "hidy" coffee has picked up "condensation in the bag and tastes like a sweaty, dirty horse." Coffee can start fermenting. Or it can become "baggy," tasting of the burlap bag it was shipped in.

Before we cup, Greisgraber takes a palmful of Sumatran and Colombian green beans, which have no smell (when it's picked, coffee smells like "sweet grass," she says); she roasts them in a small rotating barrel over a gas fire for eight minutes. At two-minute intervals, she describes the change from endothermic (taking on the heat, the first half of the roast) to exothermic (giving off the heat, the second half). During the first two-minute phase, the beans lose their moisture, brighten up, and smell like burning grass; in the second phase, they continue losing water and take on a "muffin" smell, which she calls "a bit irritating"; in the third phase, the beans crack, stretch, brown, and exude what Greisgraber calls "coffee's sweet odor"; in the fourth phase, the well-roasted, embrowned beans start to smoke, put out heat, and reach "that full coffee smell."

Greisgraber cups up to four times a day with four cups on the table each time, testing for taste, smell, consistency. The roasting done, she grinds the beans, spoons the grounds into shot glasses, covers them with 200-degree water, and lets them steep until they form a crust. The aroma is exotic. "Before the ground coffee is wet, it has a fragrance. Once it's wet, it has an aroma, and you can actually smell it off the steam." Sure enough, the wet coffee grounds smell richer than the ground coffee. To release the aroma, Greisgraber plunges a spoon through the crust and breathes in. It smells, she says, "sweet, chocolaty, full-bodied" -- all hallmarks of a good cup of joe. She smells the other glasses, checking for consistency. Next she scoops up a sample and slurps it "aggressively" into her mouth. She washes the coffee across her tongue -- "swish it around and chew it a little bit" -- and holds it several seconds before spitting it out.

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