The aroma was dynamic and unpredictable, almost like a living thing. On some hot summer days, it was thick and sweet, and when it drifted over Hagen’s neighborhood—a series of row houses by the interstate—it was as if molasses had been poured through the streets. At other times, the smell was protein-rich and savory. Many of the odors triggered specific associations—birthday cake, popcorn, chicken-noodle soup—and they stayed with her. In 1992, Hagen went to the University of Cincinnati to study art, but she soon turned to science, majoring in biology. She never imagined that she would end up working in the factory that made The Smell. The factory belongs to a Swiss company called Givaudan, the largest manufacturer of flavors and fragrances in the world, and upon graduating Hagen got a temporary job there that soon grew into something permanent. After three years of gruelling apprenticeship, she became a flavorist, a job that admitted her into a kind of secret society. There are fewer than five hundred flavorists in the United States, and they almost never speak about their work outside their laboratories.

Hagen is thirty-five. She is a brunette, with straight hair that falls just below her shoulders. She is not thin, but her face is, and it lights up easily. She prefers things that are vivid. Beneath her lab coat, Hagen is sure to be wearing some bright-hued article of clothing—a scarf, a sweater. She holds her hair back with sunglasses, in summer and in winter. After spending even a short time with her, one can’t help but think of Roald Dahl’s Willy Wonka, who believed that the manufacture of flavors—particularly the sweet and flashy ones that go into candy, chewing gum, and marshmallow—demands a childlike openness. At the end of “Charlie and the Chocolate Factory,” Wonka tells Charlie Bucket that an adult could never run his factory. “Mind you, there are thousands of clever men who would give anything for the chance to come in and take over from me, but I don’t want that sort of person,” he says. “I don’t want a grown-up person at all.” But Wonka surely would have hired Hagen. Her office resembles a walk-in high-school locker, if such a thing existed. The walls are covered with magazine clippings, photographs, and Post-its; a clock-size Swatch with a blue kangaroo painted on it; and a dry-erase board with lists of words meant to inspire flavor creation (“baobab,” “jujube,” “mamoncillo”). Tacked here and there are paint chips from Benjamin Moore, which she once used as aides to memorize the aromas of approximately a thousand chemicals. California Lilac was ethyl isovalerate; Mellow Yellow was gamma octalactone.

If you like sports drinks, or something with açaí or pomegranate or huckleberry on its label, you may well have tasted one of Hagen’s creations. Naming the products that contain her flavors, however, would undermine the confidentiality agreements that Givaudan keeps with its clients, and elicit a severe reprimand. Several years ago, a Givaudan employee attending a convention accidentally let slip to a reporter for Beverage World that the company had made a vanilla flavor for Coca-Cola. After the comment was published, Givaudan executives acted as if a state secret had been breached: they investigated the leak, restricted all information about their business with Coke to employees working directly for the company, and flew to Atlanta to visit the Coca-Cola headquarters and apologize in person. In the world of flavor, it is not enough to keep secret a chemical formula. (Typically, these formulas are not patented; hence the obscuring use of “natural flavoring” as an ingredient—and an omnipresent riddle—on food labels.) The Givaudan employee who attended the convention had broken a more fundamental rule. Few of the companies that sell processed foods or drinks want the public to know that outside laboratories supply them with flavors. Even after Snapple’s founders admitted to me that, more than twenty years ago, a Brooklyn-based company named Virginia Dare had designed the flavors for a line of sodas that Snapple has long since discontinued, people at Virginia Dare refused to discuss the matter.

Such secrecy helps shape the story of our food. It encourages consumers to think of processed foods as fully formed objects, rather than as assemblages of disparate components. It treats a brand as sacrosanct. (This is not the case in all industries: Dell openly acknowledges that the processors for its computers come from Intel.) Perhaps this kind of deception is necessary because eating and drinking are such elemental experiences. Our evolutionary forebears did not have to wonder about the supply chain of, say, an apple, and many of us today seem unwilling to register the complexity of industrial foods.