Exploring marvels of the mouth

Mary Roach / New York Times News Service /

Published Mar 26, 2013 at 05:00AM

WAGENINGEN, the Netherlands — When I told people I was traveling to Food Valley, I described it as the Silicon Valley of eating. At this cluster of universities and research facilities, nearly 15,000 scientists are dedicated to improving — or, depending on your sentiments about processed food, compromising — the quality of our meals.

At the time I made the Silicon Valley comparison, I did not expect to be served actual silicone.

But here I am, in the Restaurant of the Future, a cafeteria at Wageningen University where hidden cameras record diners as they make decisions about what to eat. And here it is, a bowl of rubbery white cubes the size of salad croutons.

Andries van der Bilt has brought them from his lab in the brusquely named Department of Head and Neck, at the nearby University Medical Center Utrecht.

“You chew them,” he said.

The cubes are made of a trademarked product called Comfort Putty, more typically used in its unhardened form for taking dental impressions. Van der Bilt isn’t a dentist, however. He is an oral physiologist, and he likely knows more about chewing than anyone else in the world. He uses the cubes to quantify “masticatory performance” — how effectively a person chews.

I take a cube from the bowl. If you ever, as a child, chewed on a whimsical pencil eraser in the shape of, say, an animal or a piece of fruit, then you have tasted this dish.

“I’m sorry.” Van der Bilt winces. “It’s quite old.” As though fresh silicone might be better.

Van der Bilt and his colleagues have laid claim to a strange patch of scientific ground. They study the mouth — more specifically, its role as the human food processor. Their findings have opened up new insights into quite a few things that most of us do every day but would rather not think about.

The way you chew, for example, is as unique and consistent as the way you walk or fold your shirts.

Van der Bilt studies the neuromuscular elements of chewing. You often hear about the impressive power of the jaw muscles. In terms of pressure per single burst of activity, these are the strongest muscles we have. But it is not the jaw’s power to destroy that fascinates Van der Bilt; it is its nuanced ability to protect.

Think of a peanut between two molars, about to be crushed. At the precise millisecond the nut succumbs, the jaw muscles sense the yielding and reflexively let up. Without that reflex, the molars would hurtle recklessly toward one another, now with no intact nut between.

To keep your he-man jaw muscles from smashing your precious teeth, the only set you have, the body evolved an automated braking system faster and more sophisticated than anything on a Lexus. The jaw knows its own strength. The faster and more recklessly you close your mouth, the less force the muscles are willing to apply. Without your giving it a conscious thought.

Teeth and jaws are impressive not for their strength but for their sensitivity, Van der Bilt has found. Chew on this: Human teeth can detect a grain of sand or grit 10 microns in diameter. A micron is 1⁄25,000 of an inch. If you shrunk a Coke can until it was the diameter of a human hair, the letter O in the product name would be about 10 microns across.

But the study of oral processing is not just about teeth. It’s about the entire “oral device” — teeth, tongue, lips, cheeks, saliva, all working together toward a singular revolting goal, bolus formation.

The word “bolus” has many applications, but we are speaking of this one: a mass of chewed, saliva-moistened food particles. Food that is in, as one researcher has put it, sounding like a license plate, “the swallowable state.”

Most of the time, while you’re just breathing and not swallowing, the larynx (voice box) blocks the entrance to the esophagus. When a mouthful of food or drink is ready to be swallowed, the larynx has to rise out of the way, both to allow access to the esophagus and to close off the windpipe and prevent the food from “going down the wrong way.”

To allow this to happen, the bolus is held momentarily at the back of the tongue, a sort of anatomical metering light. If, as a result of dysphagia, the larynx doesn’t move quickly enough, the food can head down the windpipe instead. This is, obviously, a choking hazard. More sinisterly, inhaled food and drink can deliver a troublesome load of bacteria. Infection can set in and progress to pneumonia.

The safest foods, of course, are those that arrive on the plate pre-moistened and machine-masticated, leaving little for your own built-in processor to do. They are also, generally speaking, the least popular. Mushy food is a form of sensory deprivation. In the same way that a dark, silent room will eventually drive you to hallucinate, the mind rebels against bland, single-texture foods, edibles that do not engage the oral device.

Those who can chew want to chew. We especially enjoy crunch. A colleague of Van der Bilt, Ton van Vliet, has spent the past seven years figuring out just how crunch works.

Crispiness and crunchiness appeal to us because they signal freshness, Van Vliet said. Old, rotting, mushy produce can make you ill. At the very least, it has lost much of its nutritional vim. To a certain extent, we eat with our ears.

“People eat physics,” said Van Vliet. “You eat physical properties with a little bit of taste and aroma. And if the physics is not good, then you don’t eat it.”

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