Our perception of flavor transcends the tongue

You’ve snagged a blue-marbled wedge of real English Stilton, aged and semi-soft. The stink is intense and, defying all logic, appealing. You pop a piece in your mouth and what happens next—sensorially, biochemically, neurologically, and even emotionally—is so complex that scientists are still trying to figure it all out.

To learn what they do know, I contacted the Monell Chemical Senses Center, an independent nonprofit research institute in Philadelphia that studies taste and smell. According to its experts, most of what the general public views as fact is only partly true—or flat-out wrong.

There are five fundamental taste sensations: sweet, salty, sour, bitter, and, the most recent addition to the group, umami, also referred to as savory. Pronounced oo-MOM-ee, it’s a Japanese word loosely translated as “yumminess,” which describes what we experience as rich, earthy, brothy, and meaty. Glutamate, the amino acid trigger for experiencing umami, is especially high in protein-rich and fermented foods, such as mushrooms and tomatoes, as well as in beverages. Many menu items we love—a burger with ketchup, pizza (double cheese, of course), beer and wine—pack an umami punch.

There are two common misconceptions about taste, explains Marcia Levin Pelchat, Ph.D., a sensory psychologist and associate member of the Monell Center: that taste happens only on the tongue, and that certain areas of it are devoted to just one of the fundamental five tastes.

“Specialized cells in the mouth contain clusters of receptors that recognize and react to specific substances,” Pelchat says, “in a sort of lock-and-key relationship, releasing a biochemical cascade that sends electrical signals to the brain.” The response is primal, meant to ensure we eat what we need and avoid what might be spoiled or poisonous. Most of these receptors are located in the tiny papillae, the buds or bumps we can see scattered over the surface of the lingual landscape, but they’re also found elsewhere in the oral cavity.

The well-known diagram of the “tongue map,” which assigns real estate at the tip to sweetness and at the back to bitterness, in fact has no grounding. It’s a result, Pelchat tells me, of a mistranslation of an old German text. “Researchers have not yet determined whether individual taste buds can detect one, multiple, or all taste qualities,” states literature from Monell, but studies have shown that “all areas of the tongue can recognize each taste, with some areas better at responding to certain tastes than others.”

And every tongue is unique. “It appears [that] some individuals have more densely packed papillae,” notes Pelchat. “And there are natural differences in gene structure that may account for why a particular food seems very bitter to me but not to you.”

Furthermore, we typically eat foods in combination, and those interactions have a profound influence on our perception of taste. “The salt in cheese blocks the bitterness in a big red Cabernet, so you detect more of the wine’s natural sweetness when you enjoy them together,” explains Pelchat, who is also on the board of the American Institute of Wine and Food. Consuming only one taste also makes us temporarily insensitive to it, she continues, because we adapt, becoming less aware of the dominant compounds. That’s why a pleasantly dry wine suddenly seems sour after a few bites of a sugary dessert. In the same way, vinaigrette inhibits our ability to pick up the sour notes of a wine, making it seem flat on the palate.

Most of us use the words interchangeably, but to scientists taste—the gustatory analysis that tells us which of the five basic qualities we’ve encountered—and flavor are not one and the same. Two other physiological factors come into play when we savor that morsel of Stilton. As the nose and the mouth are interconnected, aroma plays an important role in the information-gathering system of the brain. In tests, subjects who pinch their nostrils shut before putting a piece of strawberry candy in their mouths are able to pick up sweetness but cannot identify the specific fruit flavor. That’s because “strawberry” is actually a smell. We also gather essential data from what we call “feel,” which includes temperature, texture, and chemosensory irritation expressed as pungency, warmth, cooling, or tingling. When a dish delivers a wallop of spicy heat, the “burn” is conveyed through nerve endings in the mouth, throat, nose, and eyes. It has nothing to do with our taste buds.

“I think the most useful thing for people to understand is that what we call ‘flavor’ is a combination of taste, olfaction [smell], and a wide variety of tactile components,” Pelchat says. “The brain combines these multiple sensory inputs into a single experience.”

But this only partly explains why we love, and hate, specific foods. The mind, memories, and culture, Pelchat insists, play an equal, if not more significant, role in shaping flavor perceptions and preferences. The limbic system, seat of our emotional reactions, is sometimes called the “smell brain,” emphasizing the connection between the two. It’s difficult to determine whether we salivate over the scent of braised brisket or cinnamon-laced rice pudding—or whatever food traditions represent our personal past—because of biology or background. A normally unpleasant smell doesn’t seem bad once we realize it’s coming from a wonderful cheese. And in blind tastings, respondents rate wines described as more expensive on a higher scale than those thought to be from the bargain bin.

But ultimately, familiarity may be the most reliable predictor of what an individual likes. To illustrate, Pelchat tells a 1960’s-era joke, no longer politically correct but pertinent.

“A young bride cooks dinner for her husband every night,” Pelchat says. “And every night he complains, because her dishes don’t taste as good as his mother’s. Then comes the day when she burns the roast. Her spouse takes a bite, smiles, and says, ‘You finally got it right!’”

Written by Laura Taxel
Illustration by Jacqueline Rogers