7
A Bolus of Cherries
LIFE AT THE ORAL PROCESSING LAB
WHEN I TOLD people I was traveling to Food Valley, I described it as the Silicon Valley of eating: fifteen thousand scientists 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 it is, a bowl of rubbery white cubes the size of salad croutons. Andries van der Bilt 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 says.
Van der Bilt has studied chewing for twenty-five years. If a man can be said to resemble a tooth, van der Bilt is a lower incisor, long and bony with a squared-off head and a rigid, straight-backed way of sitting. It’s between meals now in the camera-rigged Restaurant of the Future. The serving line is unstaffed, and the cash registers are locked. Outside the plate-glass windows, it’s snowing again. The Dutch pedal along on their bicycles, seeming daft, or photoshopped.
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. He uses the cubes to quantify “masticatory performance”—how effectively a person chews. Research subjects chew a cube fifteen times and then return it in its new, un-cube-like state to van der Bilt, who pushes it through a set of sieves to see how many bits are fine enough to pass through.
I take a cube from the bowl. Van der Bilt, the cameras, and emotion-recognition software called Noldus FaceReader watch me chew. By tracking facial movements, the software can tell if customers are happy, sad, scared, disgusted, surprised, or angry about their meal selections. FaceReader may need to add a special emotion for people who have chosen to have the Comfort Putty. If you ever, as a child, chewed on a whimsical pencil eraser in the shape of an animal, say, 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.
The way you chew is as unique and consistent as the way you walk or fold your shirts. There are fast chewers and slow chewers, long chewers and short chewers, right-chewed people and left-chewed people. Some of us chew straight up and down, and others chew side to side like cows. Van der Bilt told me about a study in which eighty-seven people came into a lab and chewed an identical amount of shelled peanuts. Though all had a full complement of healthy teeth, the number of chews ranged from 17 to 110. In another project, subjects chewed seven foods of widely varying textures. The best predictor of how long they chewed before swallowing wasn’t any particular attribute of the food. The best predictor was simply who’s chewing. Your oral processing habits are a physiological fingerprint. As with the finger kind, most of us have no idea what ours look like.* We couldn’t pick our own chewing mouths out of a lineup, although it would be interesting to try.
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 continue to 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 is ever vigilant. It 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.
You can witness the protective cutout reflex by hooking up a person’s jaw muscles to an electromyograph. The instant something hard gives way, the readout of electrical activity goes briefly flat. “The silent period, they call it,” van der Bilt says. It seems like a term kindergarten teachers might use, or people at a Quaker meeting. All these years, I’ve had it backward. Teeth and jaws are impressive not for their strength but for their sensitivity. Chew on this: Human teeth can detect a grain of sand or grit ten microns in diameter. A micron is 1/25,000 of an inch. If you shrank a Coke can until it was the diameter of a human hair, the letter O in the product name would be about ten microns across. “If there’s some earth in your salad, for instance, you notice immediately. It warns you for the wrong things.” Van der Bilt did the experiment himself. “We took some vla . . .” Custard! In the Netherlands, vla is never far from where you are. “We put some plastic grains of various sizes in it . . .”
Van der Bilt stops himself. “I don’t know if you want to hear these things.” He has a tentative, apologetic manner of speaking, like a man accustomed to feeling that his audience, at any moment, is about to make an excuse and get up to go. Earlier he told me that his unit at Utrecht is slated to close when he retires, in a year. “There isn’t,” he said, “enough interest.”
I think it may be something else.
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 unpicturesque 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 put it, sounding like a license plate—“the swallowable state.”*
I don’t think the scientists are uninterested. I think they may be disgusted. This is a job where on any given day, you may find yourself documenting “intraoral bolus rolling” or shooting magnified close-ups of “retained custard” with the Wageningen University tongue-camera. Should you need to employ, say, the Lucas formula for bolus cohesiveness, you will need to figure out the viscosity and surface tension of the moistening saliva as well as the average radius of the chewed food particles and the average distance between them. To do that, you’ll need a bolus. You’ll need to stop your subject on the brink of swallowing and have him, like a Siamese with a hairball, relinquish the mass. If the bolus in question is a semisolid—yogurt and vla are not chewed, but they are “orally manipulated” and mixed with saliva—the work is yet less beautiful. As evidenced by this caption in a textbook chapter by my host René de Wijk: “Figure 2.2. Photographs of spat-out custard to which a . . . drop of black dye has been added.”
Humans, even physiologists, don’t like to think about food once they’ve begun to process it. The same chanterelle and Gorgonzola galette that had the guests swooning is, after two seconds in the mouth, an object of universal revulsion. No one knew this more intimately than Tom Little, an Irish American laborer who ate his meals by chewing food and spitting it into a funnel that fed into his stomach. When he was nine years old, in 1895, Tom swallowed a draught of clam chowder without letting it cool. The burn healed with strictures that fused the walls of his esophagus. Surgeons created a fistulous opening to his stomach so he could eat—or “feed,” as Tom now referred to the act of taking in sustenance. It was an undiminishing source of embarrassment. (Interestingly, his doctor noted in a book about the case, Tom “blushed both in his face and his gastric mucosa.”) He told no one, and took his meals alone or with his mother. When he finally married, it was to an older woman for whom he felt little attraction. He chose her, he told his doctor, because “she doesn’t mind the way I feed.”
In the bulimic community, the weight-loss strategy known as “chewing and spitting” (or CHSP) is by far the least popular. Only 8 percent of bulimic patients seen at the Eating Disorders Clinic at the University of Minnesota reported having engaged in CHSP more than three times a week—usually resorting to it only if they were unable to make themselves
vomit, or because regurgitated stomach acid was damaging their teeth or esophagus. Rarely would the study’s author, Jim Mitchell, encounter a patient “whose sole problem is chewing and spitting.”
Of all the unflattering and untrue stories printed in the tabloids about Elton John over the years, this one drove him to sue: “Rock star Elton John’s weight has plunged . . . thanks to a bizarre new habit of eating food then spitting it out.” The article, which ran in London’s Sunday Mirror in 1992, described him at a holiday party at his manager’s home, spitting chewed shrimp into a napkin, commenting gaily, “‘I love food, . . . but what’s the point of swallowing it, you can’t taste it as it goes down your throat.’” The editors admitted to having fabricated the story but didn’t feel John had been defamed. The jury disagreed, awarding the singer £350,000—about $570,000—in damages.
Disgust and shame don’t fully account for the unpopularity of CHSP. This does: chewing without swallowing is not eating. It doesn’t scratch the itch. That’s the point of swallowing it, made-up Elton: satisfaction. As regards eating, Mitchell told me, there’s an imaginary line at the esophagus. “Everything happening above the neck—smelling, tasting, seeing—drives you toward eating, and everything below drives you toward stopping.” Chewing causes saliva to be secreted, which dissolves the food and brings more of it in contact with the taste buds. Taste receptors recognize salts, sugars, fats, the things bodies need to thrive, and impel us to stock up. As the stomach fills and satiety grows, the head pipes down. Presently the plate is pushed away. When you chew food without swallowing it, the line at the neck is never crossed. The head keeps up its clamor.
Which brings us to another reason the incidence of CHSP is so low. It’s expensive. Some of the women Mitchell interviewed would catch and release several dozen doughnuts at a go, flushing twenty-plus dollars down the toilet.
JIANSHE CHEN CAN tell you the flow speed of a high-viscosity bolus.* He knows the shear strength of a ricotta-cheese bolus, the deformability of Nutella, the minimum number of chews required to ready a McVitie’s Digestive biscuit for the swallow (eight). On the Internet I found a copy of Chen’s PowerPoint on the “dynamics of bolus formation and swallowing,” so I too know these things. What I don’t know is the point of it all. Chen made the mistake of putting his University of Leeds e-mail address on the website.
He wrote back right away. You get the sense oral processing experts are not, generally speaking, besieged by media inquiries. The aim of the work, he said, is to “provide guidance on how to formulate foods for safe eating by disadvantaged consumers.” Bolus formation and swallowing depend on a highly coordinated sequence of neuromuscular events and reflexes. Disable any one of these—via stroke, degenerative neurological condition, tumor irradiation—and the seamless, moist ballet begins to fall apart. The umbrella term is dysphagia (from the Greek for “disordered eating,” which may or may not explain flaming Greek cheese appetizers).
Most of the time, while you’re just breathing and not swallowing, the larynx (voice box) blocks the entrance to the esophagus (food tube). When a mouthful of food or drink is ready to be swallowed, the larynx has to rise out of the way, both to yield access to the esophagus and to close off the windpipe and prevent the food from being inhaled. 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.
A less lethal and more entertaining swallowing misstep is nasal regurgitation. Here the soft palate—home turf of the uvula,* that queer little oral stalactite—fails to seal the opening to the nasal cavity. This leaves milk, say, or chewed peas in peril of being horked out the nostrils. Nasal regurgitation is more common with children, because they are often laughing while eating and because their swallowing mechanism isn’t fully developed.
“Immature swallowing coordination” is the reason 90 percent of food-related choking deaths befall children under the age of five. Also contributing: immature dentition. Kids grow incisors before they have molars; for a brief span of time they can bite off pieces of food but cannot chew them. Round foods are particularly treacherous because they match the shape of the trachea. If, say, a grape goes down the wrong way, it blocks the tube so completely that no breath can be drawn around it. A child is better off inhaling a plastic barnyard animal or toy soldier, because air can be inhaled through its legs or around its rifle. Hotdogs, grapes, and round candies take the top three slots in a list of killer foods published in the July 2008 issue of the International Journal of Pediatric Otorhinolaryngology, itself a calamitous mouthful. Jennifer Long, a professor of head and neck surgery at the University of California, Los Angeles, went so far as to declare hotdogs a public health issue. A candy called Lychee Mini Fruity Gels has killed enough times for the U.S. Food and Drug Administration to have banned its import.
Every now and then a food comes along that is so difficult to orally process that even healthy adults without dysphagia have trouble getting it down. Sticky rice mochi, a traditional Japanese New Years food, kills about a dozen people every year—along with puffer fish and flaming cheese, the world’s riskiest menu items.
The safest foods, of course, are those that arrive on the plate premoistened 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. Mush is for babies. Those who can, want to chew. The story of U.S. military rations bears this out. During World War II, when combat rations were tinned, meat hashes were a common entrée because they worked well with the filling machines. “But the men wanted something they could chew, something into which they could ‘sink their teeth,’” wrote food scientist Samuel Lepkovsky in a 1964 paper making the case against a liquid diet for the Gemini astronauts. He summed up the soldiers’ take on potted meat: “We could undoubtedly survive on these rations a lot longer than we’d care to live.” (NASA went ahead and tested an all-milkshake meal plan on groups of college students living in a simulated space capsule at Wright-Patterson Air Force Base in 1964. A significant portion of it ended up beneath the floorboards.)
The only thing sadder than swallowing mush is not swallowing at all. Tube-feeding is a deeply depressing state of affairs. Rather than chew and spit out his food, Tom Little—the Irishman with the strictured esophagus—could have mashed it and pushed it directly into his stomach. In fact, he tried this, but without chewing, it “failed to satisfy.” (Beer, however, was poured directly into the funnel.) Here’s how badly people want to chew. Recall that dysphagia may knock out the reflex that repositions the larynx (voice box) to allow food into the esophagus. Jennifer Long told me these patients have on occasion asked to have their voice box surgically removed so they can swallow again. In other words, they would rather be mute than tube-fed.
Crispy foods carry a uniquely powerful appeal. I asked Chen what might lie behind this seemingly universal drive to crunch things in our mouths. “I believe human being has a destructive nature in its genes,” he answered. “Human has a strange way of stress-release by punching, kicking, smashing, or other forms of destructive actions. Eating could be one of them. The action of teeth crushing food is a destructive process, and we receive pleasure from that, or become de-stressed.”
I run this by René de Wijk when I get back to his house in the evening. He is slouched on the sofa, his frizzy hair falling in clumps on his forehead. His son sits between us, playing Assassin’s Creed on the TV screen. A man in a cowled robe is doing some de-stressing, bludgeoning people and slicing them in two with a broadsword.
René
agrees with Chen’s assessment. “With crispy, it’s so obvious that you’re destroying the food in order to get your sensation. What is more marvelous than to control a nice structure with your mouth?” René doesn’t know offhand of any studies on the psychology of crunchy food, but he promised to e-mail a colleague, Ton van Vliet, a food physicist who has devoted the past eight years of his career to a deeper understanding of crispy-crunchy.
The assassin bisects another citizen while René and his wife discuss the thermostat. The heating people have been out to fix it, and now they’re coming back because it’s on the fritz again. I point the toe of my boot at the TV. “That guy seems effective. Get him on board.”
René looks at the screen. “He has his creed, he would kill the heating people!”
I was originally to have spent the afternoon with René in the Wageningen University Oral Lab. He had promised to wire me up to the articulograph and generate a 3-D profile of my chewing style, but he couldn’t recall which sensor went where. I sat with a beard of colored wires hanging from my cheeks while René flipped through the manual. And then he had to leave for a meeting.
Nonetheless, he’s been very effective at persuading other harried researchers to let me eat up their time. Ton van Vliet has agreed to meet us the following day at my home-away-from-home, the Restaurant of the Future.
VAN VLIET IS there when René and I arrive, sitting with his back to us at a table in the middle of the room. René recognizes the white hair. The longer strands appear to originate from a source at the back of the head and travel forward from there. All I can guess is that he walked here with a fierce wind at his back.
Van Vliet looks up as if from deep thought, a little startled, and extends his hand. He has a fine-boned face accented by an Amish-style beard and delicate-looking wire-rim glasses. I don’t want to use the word elfin, in case it seems belittling, but it did come to mind.