Taste: Surprising Stories and Science About Why Food Tastes Good (18 page)

This was not what I expected to hear when talking to a chef about texture. I went into the discussion with Skenes thinking that a chef’s attention to the tactile sense is focused primarily on
food
texture. But of course it makes sense that physical comfort is part of the pampering experience of fine dining. Now that I’ve experienced it at Saison, I think that providing a blanket on the back of a restaurant chair should be standard restaurant procedure. Swaddling yourself in microfiber takes the idea of luxury dining to the next level, especially in San Francisco when a 40° summer night can chill you to the bones.

Food texture is determined by the chemical interactions between the network of molecules in a food. This is an unappetizingly clinical way of describing the texture of food, yet it is the specific arrangement of molecules that makes a banana different from a pretzel. This includes the strength of the bonds between the molecules, the way those molecules change when the food changes temperature in your mouth, and the way the food changes form as it starts to dissolve in your mouth.

Fruits and vegetables get their distinctive textures from the bonds in the cell walls. This is what makes a tomato different from a tomatillo. Of course, the molecules in both change tremendously when these foods are handled, cooked, chilled, frozen, or stored for a period of time. A fresh tomato has a very different texture from a canned tomato, because the cell walls of the fresh tomato are intact. When a tomato is heated during the canning process, the cell walls break down, which results in a change in texture. The same thing happens when you freeze a tomato (or other foods). Once the cell walls are frozen, they’re forever changed. Thawing a frozen tomato will reveal the broken cell walls in two ways: the tomato will be less firm than it was when it was fresh, and the water that was in those cell walls will drain freely out of the tomato.

If we wanted to do a sensory evaluation of the texture of tomatoes, we would start by developing a lexicon—a group of words—to describe it. This would include words like
juiciness
, which might not seem like a word to describe texture, but what causes a tomato to be perceived as juicy (or not) is the texture. A fresh tomato will have a lot of moisture stored inside its intact cell walls. An oven-dried tomato will not.

Tomato Talk

A Lexicon for the Textural Attributes of Fresh and Processed Tomatoes

Adapted from the paper by Pairin Hongsoongnern and Edgar Chambers IV

One word we use for texture in common English is
consistency
, as in “How is the consistency of that cream of tomato soup?” In this case, the word
consistency
means texture. But the word has another meaning, too. Consistency can mean the degree of conformity, such as “Roger’s levelheaded behavior lends a steady consistency to our relationship.” In this case, it means “a harmonious uniformity.”
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You can see how this word could cause problems when it is used to evaluate food. Consider the sentence, “This batch of tomato soup is not as good as the last. I’m having trouble with the consistency.” Does this mean that the soup maker is having trouble with the thickness or having trouble duplicating the recipe from batch to batch? It’s unclear. To avoid this confusion, I prefer the term
viscosity
instead to describe texture.

Most people think of astringency as a type of bitterness. This is not really the case. Many bitter or sour foods are also astringent, which is probably where the confusion comes from. But astringency is detected with the trigeminal or (touch) nerve. It is a texture. Some of the most common, well-known astringent compounds are tannins, which give red wine, coffee, and tea their tannic, drying mouthfeel. Another favorite astringent is alcohol, which is dehydrating. When alcohol dehydrates it, the tongue feels like it’s been dried out. That drying feeling is astringency.

Tannins act on your tongue by making certain mucoproteins in your saliva poke out and puff up their chests. These proteins don’t play well with other proteins, which results in a dustup in the playground of your mouth. This clash causes friction, which means that your saliva is less lubricating. The result is that your mouth feels dry. This is astringency from tannins.

In order to feel the astringency from tannins, you need only a red grape, the redder or darker the better. Be sure to choose a juicy one, rather than a firm one. Put the grape in your mouth and, without using your teeth, mash the grape up against the roof of your mouth with your tongue and work it until you’ve entirely separated the skin from the juicy insides. Then swallow the sweet and sour innards of the grape, but keep the grape skin in your mouth. Now you’re ready to experience the sensation of astringency. Put the grape skin on your back molars and start chewing. Keep chewing until you start to feel something that’s drying or perhaps puckery. That is astringency. You can now taste the distinctiveness of astringency and understand why it is commonly confused with the Basic Taste bitter. Astringency is the tactile sensation you’re feeling on your tongue.

Tannins are also known as
polyphenols
, which are healthful antioxidant compounds found in plants. Some tannins occur in red wine and come from the crushed skins of the grapes. They’re also present in tea, coffee, pomegranates, and nuts. These foods are usually balanced with a counterpoint Basic Taste or two. The astringency in tea, for example, is often balanced with a sour squirt of lemon and/or a sweet spoonful of sugar. Red wine makers strive for the perfect balance of tannin, acidity, and sweetness. Since astringency results from a decrease in lubrication, it would make sense that a good way to balance tannic foods is with something slick, like fat. That’s exactly what adding cream to coffee accomplishes. The classic pairing of red wine with steak taps into this as well.
The fat in a piece of red meat is the perfect way to lubricate the tongue between sips of astringent, drying Sangiovese or cabernet sauvignon.

The space inside the adult male mouth can hold about thirty grams of water; the female mouth, about twenty-six grams. You hold water in your mouth only about one second before swallowing it, because water doesn’t have much taste or aroma, so you don’t have any reason to keep it in there longer to savor it. Also, because it’s thin and liquid, you don’t have to do much to prepare it to be swallowed. The thicker the liquid, the longer you keep it in our mouth. You hold honey in your mouth for about three seconds before swallowing it. When you eat solid food, this changes even more dramatically. For instance, a man will take a mouthful of banana that averages about eighteen grams, and a woman about thirteen grams, about half as much volume as water. This is because you need extra free space in your mouth to be able to move solid food around to manipulate it before swallowing.

You use your teeth to feel texture in several ways: to grip food, bite off pieces, and chew to reduce the size of the food until it is small enough to be swallowed. Another way your teeth help you detect food texture is through their nerve fibers. When you use your teeth to apply pressure to food, that pressure jiggles the teeth in their sockets ever so slightly, sending information along the nerve fibers to the central nervous system to identify food texture, often unconsciously.

If I say the word
muscle
, the first image that pops into your head is likely one of a curled biceps, bulging from the weight of a barbell, or some other similar image of an arm, leg, or torso. We almost never think about the tongue as a muscle, yet that’s exactly what it is. You use the power and finesse of the muscles in your tongue to move food in the mouth just as you use the muscles in your arms to move bags, babies, books, and barbells.

Saliva greases the skids in identifying and appreciating food texture. Its lubrication allows the tongue to move the food around easily. Without saliva, we wouldn’t be able to moisten food enough to form it into a ball (the yummy-sounding wad or bolus) to be swallowed. The saliva glands act as the irrigation system of the mouth, releasing moisture when it’s needed and cutting it back when it’s not. Salivary glands shut down for the night when we go to sleep, which is why we wake up with a dry mouth and bad breath. Because saliva isn’t needed for irrigation during sleep, it doesn’t refresh the mouth then as it routinely does when we’re awake.

Swallowing is the final phase of food texture detection. The active part of swallowing happens when the tongue forms food into a bolus and passes it to the back of the mouth. Once it’s there, throat muscles contract to aid in swallowing farther down your gullet. These automatic reflexes, surprisingly, don’t rely on gravity. The reflexes that move food down the throat will work even if the muscles are anesthetized or if you are hanging upside down. This is why astronauts can successfully eat and drink in zero gravity.

Our perception of food texture is influenced by the sound of the food we eat. If you put a potato chip into your mouth and don’t hear a crunching sound, you won’t need much more information to know that the chip is stale, wet, or under-cooked. In one study, researchers wanted to see if they could influence consumers’ perception of texture by manipulating the sounds they heard while eating. They chose to test potato chips and in order to measure the sound, they needed to ensure that every chip tested was exactly the same, an almost impossible task with regular potato chips. Their solution was a stroke of genius: they used Pringles, surely the most uniform potato chip on earth.

Once again, the subjects in the study were outfitted with headphones, as in the crossmodality experiment Linda Bartoshuk did when she tried to match the sweetness of a Coke to sound. Whereas Bartoshuk asked her participants to adjust the sound, here the researchers varied the volume for the participants. As the participants bit into Pringles—all perfectly identical in size and shape—the researchers changed the decibel level of the sounds they played. When the overall crunching sound of the chip was increased, the chips were rated significantly crisper and fresher. When it was lowered, the chips were rated more stale and soft.

What would happen if you could keep all of your other senses working but you were able to remove texture from the equation? Could you even tell what you were eating? You remove the texture from an orange when you juice it, and you can certainly tell how orange juice savors, right?

Source: Susan S. Schiffman et al., “Application of Multidimensional Scaling to Ratings of Foods for Obese and Normal Weight Individuals,”
Physiology & Behavior
21: 417–22; and Susan Schiffman, “Food Recognition by the Elderly,”
Journal of Gerontology
32, no. 5 (1977): 586–92.

Researchers tested this theory by having three groups of test subjects (healthy college students, obese, and elderly) taste different foods without the normal textural cues.
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They gave the subjects samples of various foods, cooked until soft and pureed until they all had approximately the same mouth-feel (at least as close as the researchers could get; they had to adjust some of the foods with water). They also included four of the five Basic Tastes in their test: salt, coffee (for bitter), sugar (for sweet), and lemon (for sour), which they blended with cornstarch to match the mouthfeel of the pureed solid foods. The subjects were not allowed to see the foods. But they were allowed to nose-smell them before eating, and after they put the food in their mouth, they were allowed to swish it around to experience the taste and mouth-smell of whatever it was.

Without the textural clues that are normally present, more than half of the participants had trouble identifying familiar, everyday foods such as beef, pear, and broccoli. Some foods with flavors that are unmistakably strong and characteristic, such as green pepper (vegetal, green), were much more difficult to identify. Only 19 percent of healthy students could identify pureed green peppers. Thus it seems that for many foods, we need our sense of touch to know even the most basic information—namely, what it is we’ve just put in our mouth.