Taste: Surprising Stories and Science About Why Food Tastes Good (15 page)

It would stand to reason, then, that we’d be really good at smelling something with our eyes closed and naming the smell. But we’re not. Research has proved again and again that we bomb at this task. It’s difficult to pull the names of aromas out of thin air, mostly because we just don’t learn this skill. Food aromas come in through our mouth accompanied by taste, texture, temperature, a visual glance, and, most important, context. Separating these sensations and then putting a name to the smell piece of the puzzle isn’t naturally in our repertoire of skills.

On the Bravo television show
Top Chef
, cheftestants are put to the quick-fire challenge “Name That Ingredient,” which shows just how hard this is—even for highly experienced, classically trained chefs. In a “Master Chefs” episode, professional chefs Rick Moonen, Susur Lee, and Jonathan Waxman faced off over a Thai green curry sauce with twenty-nine ingredients. Thai green curry sauce is incredibly aromatic, full of exotic ingredients such as galangal, fermented fish sauce, kaffir lime leaves, and lemongrass. I would have bet that a simple sniff would have given them all the information they would need, yet they were allowed to taste the sauce as well, giving them more assistance from their sense of taste and retronasal olfaction. Then they had to name an ingredient, one at a time. The first chef to name something that was not in the sauce would be eliminated.

Jonathan Waxman knew right away what he was tasting. “I have a fantastic wine palate, so I think my sauce palate is pretty good. Obviously, it’s a Thai curry sauce. That was kind of easy,” he told the camera. Yet Waxman was eliminated from the challenge when he named butter as an ingredient, after only four other ingredients had been named (coconut milk, garlic, lemongrass, and kaffir lime leaf). Waxman blamed his slip-up on trying too hard to make a bold proclamation, but the fact that he missed on the fifth ingredient is more than just a bit interesting.

It just so happens that our ability to discriminate odors in a mixture (think: sauce, dressing, soup) is actually limited to four. This statistic is astounding when you consider how many ingredients go into most recipes. This task seems so simple on the surface; yet even masters chefs fail regularly at it.

But all is not lost! Research has also proved that learning and practice can improve our ability to discriminate aromas. Wine tasters are better able to put a name to what they smell in a wine goblet than nonprofessionals are. Ordinary people who work in perfume stores are much better at correctly putting a name on a smell than people who don’t work with perfume.

My own professional experience has also borne this out. If you want to improve your ability to “name that food” by smell alone, I suggest you do the Spice Rack Aroma Challenge exercise. Being able to name a spice by smell alone seems easy—especially if you cook with spices often. Yet this task frustrated me for weeks until I practiced over and again. Now I can tell clove from cardamom, thyme from marjoram. But if you mix together more than five or six of the spices I know by smell, you’ll likely stump me after the first three or four. On the plus side, though, you’ll have given me a warm-and-fuzzy Fragrant Flashback to my childhood in Baltimore.

If you’re new to this, a good way to drive yourself completely crazy is to sniff a spice and—from that alone—try to identify what it is. Instead, try to identify the aroma category that it falls into. For example, is it a warm spice, such as the type of ingredient you use to make pumpkin or apple pie? If yes, then what spices fall into this category? A few that come to mind are cinnamon, nutmeg, clove, and allspice. Is the smell musky, sweaty, or animal-y? These are the aromas I get from cumin or white pepper. Is it grassy? Dried dill and parsley smell of lawn cuttings to me. Identifying the aroma category will allow you to narrow down the list of choices from the entire universe of herbs and spices to a subset of them. This way, you’ll drive yourself only semicrazy.

Since identifying an aroma out of thin air is so difficult, how are patients who complain of loss of smell evaluated? If you were to give them a sniff of something, how would you know whether they could smell it or not? Most people find this task difficult when their senses of smell and taste are working! Instead, doctors generally use some form of a multiple-choice test.

Others use an olfactometer, a special piece of equipment that puffs volatile aroma molecules into a tube or cylinder that you lean in to sniff. A computer screen or paper gives multiple choices for what you smell. By varying the concentration levels of the aromas, an olfactometer can measure not just whether you can smell or not, but how sensitive your sense of smell is.

An annual checkup at the doctor’s office may include an eye and ear exam, but it rarely includes a test of your ability to smell. This is a terrible oversight, since loss of smell can put your health in danger. Loss of smell changes how palatable your food is, often affecting how much and what you eat. It also puts you at other risks, too, if you can’t smell gas leaks, the smoke from a smoldering fire, or food that has spoiled.

Doctors don’t even need an expensive piece of equipment for conducting smell tests. There’s a standard paper test in the industry called the UPSIT: the University of Pennsylvania Smell Identification Test. It’s a handy little booklet of scratch-and-sniff questions that your doctor can administer in minutes. You scratch a brown patch of microencapsulated aroma and fill in the circle next to your answer, as you did on the SATs. Your choices are compared against the answer key for scoring. There’s even a way the test can determine if you are purposefully making the wrong choices. This is to identify people who visit their doctor hoping for an insurance settlement, falsely claiming they’ve lost their sense of smell.

The Brief Smell Identification Test and the University of Pennsylvania Smell Identification Tests rely on multiple-choice questions, because humans are so bad at naming an odor without a hint. A typical scratch-and-sniff question looks like this.

This odor smells most like:

a. fruit

b. cinnamon

c. woody

d. coconut

You can test yourself by ordering a kit from
www.tastewhatyouremissing.com
.

Harry Klee is a professor at the Horticulture Sciences Department at the University of Florida. His lab is working to understand the chemical and genetic makeup of flavor in fruits and vegetables. The research he is most excited about these days is called The Tomato Project. Klee is motivated by the frequency with which we consumers purchase beautiful, intensely colored tomatoes that leave us heartbroken upon the first bite.

Said Klee, “Since the 1980s, we’ve known that the tomatoes being sold in the store were crap. They suck.”

Alice Waters, the doyenne of local and seasonal cuisine, says that this is because the U.S. industrial food system is all wrong and people should eat only local, seasonal produce. Her organization, The Edible Schoolyard, puts gardening into the public school curriculum so that students get to grow their own tomatoes from heirloom seeds. This type of tomato ripens into a delicate, juice-packed monster that tastes better in part because it’s grown from heirloom seeds, in part because it’s eaten shortly after being picked. Yet for farmers to sell heirloom produce, they have to carefully transport their flavorful, water balloon–like tomatoes only a few miles from the farm. They can sell the tomatoes in small though expensive quantities during only a few months of the year. For these few months, the consumer is happier and healthier, with a tomato that tastes like a tomato, and the farmer has a few more dollars in his pocket. Yet most of the produce in the United States is shipped from where it was grown to where it will be consumed by airline or truck, a process that would destroy heirloom tomatoes.

Harry Klee believes that, by understanding what makes those heirloom tomatoes taste so good, we can reengineer them to survive being picked in Florida and shipped by truck to Minnesota in February without sacrificing flavor. Don’t let this scare you. The technique Klee is using is not genetic engineering. It’s conventional crop breeding, which farmers have been doing for hundreds of years. To breed the best tomato, though, he needs to know every single chemical molecule that makes up tomato flavor and then figure out which of the molecules are considered delicious. But what
is
tomato flavor?

“Tomato flavor basically is sugars, acids, and volatiles,” says Klee. “You have to have sugar. You have to have acid. The balance of those two is very critical to good flavor. You have to have the foundation of sugars and acids, but we believe the volatiles are where the action is. You can’t take sugars and acids and reconstitute tomato flavor.”

To reconstitute tomato flavor, you could start with a piece of equipment called a gas chromatograph mass spectrometer (GC-MS), which is what many fragrance companies use to map aromas. This machine reads the volatile aromas of a food. Feed this mysterious black box a ground-up fresh tomato and it spits out the list of volatiles that are present in the sample, along with a spiky diagram of the strength of each, regardless of whether the volatile smells are at concentration levels humans can smell or not. Yet holding this list in your hand is like reading the ingredient statement on a can of Coca-Cola. Knowing that it contains carbonated water, sugar, caramel color, phosphoric acid, natural flavors, and caffeine isn’t enough to let you whip up something that tastes like Coke. Nor does it tell you which ingredients are in the recipe for what reasons. A reading from a GC-MS gives you this kind of information, but it’s never the whole story. The results of the black-box GC-MS test are just as useless for knowing which volatile components of the tomato make us like it. This is what Klee is trying to figure out.

While there are only five Basic Tastes, the number of aromas that exist is far larger. There are about 400 volatile aromas in a tomato, many of them at levels too low for humans to detect. There are only about fifteen volatile chemicals that give a tomato its characteristic flavor.

“The interesting thing to me about tomatoes is that not one of those chemicals would really jump out at you as tomato flavor if you smelled it,” says Klee.
This is not true of every food. For example, cinnamon has one dominant, signature volatile compound (cinnaminic aldehyde); the same is true of cloves (eugenol) and butter (diacetyl).
⁵

“Tomatoes don’t have that,” says Klee. “It’s the sum of the parts that gives you tomato aroma.” The list of the volatile compound “parts” of a tomato that humans can smell is shown below. For example, there are green, grassy notes that smell a lot like the cut grass that lies atop your yard after you mow. And they’re very important to tomato flavor. In fact, says Klee, those tomatoes you buy on the stem are taking advantage of this fact. “It’s an incredible gimmick. People buy the cluster tomatoes. In the store they pick up the cluster and they smell it and they say, ‘Oooh, that smells good.’ They’re not smelling the tomato. They’re actually smelling the vine.”

The Naturally Occurring Volatile Compounds That Make a Tomato Savor Like a Tomato