From The New York Times:
The food technicians stopped worrying about inventing new products and instead embraced the industry’s most reliable method for getting consumers to buy more: the line extension. The classic Lay’s potato chips were joined by Salt & Vinegar, Salt & Pepper and Cheddar & Sour Cream. They put out Chili-Cheese-flavored Fritos, and Cheetos were transformed into 21 varieties. Frito-Lay had a formidable research complex near Dallas, where nearly 500 chemists, psychologists and technicians conducted research that cost up to $30 million a year, and the science corps focused intense amounts of resources on questions of crunch, mouth feel and aroma for each of these items. Their tools included a $40,000 device that simulated a chewing mouth to test and perfect the chips, discovering things like the perfect break point: people like a chip that snaps with about four pounds of pressure per square inch.
To get a better feel for their work, I called on Steven Witherly, a food scientist who wrote a fascinating guide for industry insiders titled, “Why Humans Like Junk Food.” I brought him two shopping bags filled with a variety of chips to taste. He zeroed right in on the Cheetos. “This,” Witherly said, “is one of the most marvelously constructed foods on the planet, in terms of pure pleasure.” He ticked off a dozen attributes of the Cheetos that make the brain say more. But the one he focused on most was the puff’s uncanny ability to melt in the mouth. “It’s called vanishing caloric density,” Witherly said. “If something melts down quickly, your brain thinks that there’s no calories in it . . . you can just keep eating it forever.”