Taste: Surprising Stories and Science About Why Food Tastes Good (13 page)

Consider a world-class meal at a restaurant like Cyrus. Chef Keane has been through professional training and practice, and he clearly shows creativity and talent at the stove. A dish at Cyrus is a work of art. Extremely perishable art, but art nonetheless. Your tongue draws the outline of the food with the five Basic Tastes, the way a paint-by-numbers drawing looks before you fill in the sections. You can glean only so much detail from your tongue, though, because its palette is made up of only five tastes: sweet, sour, bitter, salt, and umami. Eating a meal without your sense of smell would be like viewing a great painting as an early, unfinished sketch. Without smell, you would experience coffee as bitter water. Milk would be slightly sweet water, and lemonade would be simply sweet and sour.

Because you cannot smell a food unless its aroma volatilizes or evaporates into the air, smell molecules are called
volatiles
. Some foods, such as citrus fruit, contain lots of volatiles. Others, such as salt, have few or none. Simply applying heat can help release the volatile aromas of food: A loaf of bread on the counter doesn’t have much of an aroma—but put it in the oven for a few minutes and soon your kitchen will smell of fresh-baked bread as the loaf’s volatile aromas
are released by the heat of the oven. This is a great trick for getting more aroma out of just about anything. If it’s lacking in smell, put it in the oven for a short period of time to release some volatiles. I do this with all bread, regardless of how fresh it is. Unequivocally, warm bread is better than the alternative because it has more volatiles and hence more flavor (not to mention other yum-producing texture and flavor changes). It never fails to amaze me how few restaurants take advantage of this simple act, which can increase sensory input for practically zero extra money or effort. I also put crackers, tortilla chips, and potato chips in the oven sometimes, just to shock the aroma molecules awake. You have to be careful doing this, though, as they’re dry to begin with, so they burn easily. I heat them for about two minutes in a preheated 400°F oven.

Once the potent aromas of the food you’re eating travel from your mouth up to your nose by means of mouth-smelling, you’ll experience the signature flavor of the food. It’s the aromas of a food that fill in the lush, saturated detail of the work of art.

At RN74, a bustling San Francisco restaurant, I recently enjoyed a perfectly cooked snow-white halibut in a beurre blanc sauce. Without my sense of smell, I would have experienced only two Basic Tastes in the sauce: sour from lemon juice and wine plus salt from salt. When I recognized the aromas of the citrus, the oaky, buttery fermentation aroma from the chardonnay, and the dairy notes from the butter that combine to make this classic recipe, it became a fully realized beurre blanc sauce.

The estimate that 75 to 95 percent of what we taste is actually smell lines up pretty well with the illustration below. The black outlines represent a very small percentage of the volume of the picture. The real beauty comes from the combination of the Basic Taste outlines from your tongue and the majority of the picture, which is what they give structure to: smell, from both your nose and mouth.

The Five Basic Tastes Draw the Outlines

Aromas Fill in the Detail

When I swallowed a bite of the halibut with the white wine and butter sauce, I also swallowed the smell of it. Literally. The aromas that you detect in your nose are actually physical things. Many people think smell is like sound, which we cannot see or touch, but this is not at all true. You can capture sound electronically or digitally, but you can’t capture sound particles. In contrast, you can capture the “particles” of smell—the volatile molecules that enter the air surrounding an object—even though they are submicroscopically small. You pull them into your body with each breath. If you smell it, you ingest it. This is a wonderful image to keep in mind as you consider an exquisite plate of food in front of you, such as the halibut with the beurre blanc wafting odors of the ocean and butter and wine into your body. It’s a bit more disturbing when you consider the smells you encounter in a bathroom or behind the exhaust pipe of an eighteen-wheeler. Have no fear, though, as smell molecules are generally not absorbed into the bloodstream.

The inside of your nose is lined with a very thin layer of mucus. It’s always there, even if it isn’t dripping out of your nostrils or down your throat from a cold or allergic reaction. This mucus layer is full of tiny hairs, or cilia, that wave back and forth in the mucus in a motion similar to the way human hair or seaweed moves when it is underwater. Once a smell is captured in the mucus, these hairs wave back and forth and flush the smell particles down your throat. If you’re breathing (which I will continue to advocate throughout the book), you’ll further enhance your ability to detect the flavor of the food by smelling it not only through your nose orthonasally, but also through your mouth, retronasally. The cilia also act as antennae that help hold onto the aroma particles as they are absorbed into the olfactory receptors inside the nose. All of this happens almost instantaneously, resulting in the recognition of a smell:
That’s a tomato.

When you have a cold, this always-present mucus layer gets thicker. If your cold is bad enough, the mucus may be too thick to allow smells to penetrate it. If a smell can’t penetrate the mucus layer, you won’t detect it. If you want to savor more while you’re sick, you could take a decongestant, which would thin and dry the mucus so that smells are able to penetrate it once again. But as long as one of your nostrils works, you can smell. Even though you have two of them,
research has proved that you can’t tell which side of your nose is doing the smelling. So don’t sweat it if only one side is stuffed up. Your brain won’t know the difference.

Once a smell penetrates the mucus and binds with a smell receptor cell at the top of the nose, there’s an electrochemical change in the cell that fires off a message to the brain. The smell nerve is cranial nerve I, which runs up through the bridge of the nose directly into the brain cavity.

Nerves in the Head That Play a Role in Taste and Smell

The discovery of olfactory receptors was so hungrily anticipated and important that the two people who found them, Linda Buck and Richard Axel, won the Nobel Prize. Here, Axel compares the complexity of smell to sight:

In the eye, we can discriminate several hundred different hues, and we do so with receptor molecules that recognize different wavelengths of light but we only have three such receptor molecules. In the olfactory system, there are at least a thousand . . . There are a thousand [olfactory] points in the brain. A given odor will activate a “set”—what we call a combination—of those points, so that the quality of an odor would be determined by a spatial pattern of neuroactivation in the brain. Every odor we have examined has a different signature that is represented by the spatial pattern of neurofiring in the brain.

This “odor signature” also communicates with the brain region where your memory of odors is matched with the odor you’re smelling. The many different experts on olfaction I’ve talked to generally agree that our preferences for smells are learned. Clearly, we can learn to associate a smell with a certain experience.

I grew up in Baltimore, Maryland. The Inner Harbor of the Chesapeake Bay, which is Baltimore’s downtown hub, used to be home to McCormick, the world’s largest spice company. The McCormick spice processing facilities operated downtown while I was a child,
⁴
releasing into the city aromatic, spiced air, which hung over downtown like a wonderful cloud of kitchen aromas. It wasn’t until I was much older—at work—that I realized that my hometown had a distinct smell. One of our employees at Mattson was busily emptying out old containers of spices and had dumped a bunch of random spices into a trash can. Imagine a mixture of cinnamon, thyme, black pepper, cumin, oregano, dill, celery salt, cardamom, clove, and a dozen other dry spices. I happened to pass the trash can and when I got a whiff of the contents, I froze. With one inhalation, I was transported home, to my childhood, standing in the Inner Harbor with my parents. Since I’d left Baltimore, I hadn’t encountered that odd, completely unintentional blend of spices.

This is the power of aroma: the ability to make a grown woman stick her head into a trash can and tear up. Smell can move us in this way because of our anatomy: olfaction is the only sense that does not first pass through the brain’s sensory switchboard, the thalamus. It essentially shortcuts its way straight to the boss man without having to deal with his minions. A very powerful sense, indeed.

The first time a signal from a smell reaches your brain, it etches a signature into your memory. I experienced what I call a
Fragrant Flashback
standing over that trash can of spices. A wonderful scene in Disney’s
Ratatouille
also illustrates this concept when the most wonderfully named food critic, Anton Ego, digs into a dish of chef Remi’s piping hot vegetable ratatouille and is instantly transported back to his childhood. This is not because childhood is where we encode our smell memories, but because Ego was a child when he first experienced ratatouille and I was a child when I first smelled the aroma of dozens of spices mingled together. If you smell ratatouille for the first time at age thirty-seven, you will connect it to that thirty-seven-year-old period of your life the next time you smell it. Smell memory is so strong it can take you back to the first time you
experienced a food. It just so happens that we experience most food for the first time when we’re young.

Personal history, culture, and learning determine our smell preferences. Linda Bartoshuk says that our sense of smell acts as an emotional sponge:

If you sniff an odor and some predator takes a bite out of you, you’re going to learn that predator is bad news. Even better, you eat something with an odor, now if you get calories from the food that odor was in: wow! That food is registered in your brain as something very good for you. Something bad happens to you, the olfactory signal is disgusting to you; something good happens to you, you love that smell.

This concept is called
conditioned preference
or
conditioned aversion.
You are conditioned to like or dislike a food in part by your experiences that accompany ingestion of it. It’s also similar to the response Pavlov was able to condition in his dogs. The dogs associated the sound of a bell with being fed. Eventually the bell, alone, could make them salivate.

But even if you and your blood sibling grew up in the same ratatouille-eating household, this doesn’t mean that you’ll both have the same reaction to the dish’s aroma. In addition to our personal histories, our sense of smell is as much as matter of genes (or nature) as it is how we’re brought up (or nurtured). Our genes determine how intensely we can smell things in the same way that they make some of us HyperTasters and some Tolerant Tasters.

Some people are genetically predisposed to specific anosmias: the inability to smell a specific compound, or smell-blindness. A few of these are widely known—for example, after eating asparagus, many people notice that their urine has a strong odor that is somewhat vegetal, sulfurous, petroleum-like, and tinny. Others are completely oblivious to this smell. Almost everyone who eats asparagus produces urine with an “off” odor, but if you’re lucky, you’re smell-blind to it. This phenomenon exists for many other odorous compounds as well.