What Einstein Told His Cook (2 page)

O
F OUR FIVE CLASSICALLY
recognized senses—touch, hearing, vision, smell, and taste—only the last two are purely chemical in nature, that is, they can detect actual chemical molecules. Through our remarkable senses of smell and taste, we experience different olfactory and gustatory sensations from contact with the molecules of different chemical compounds.

(You’ll be seeing the word molecule frequently throughout this book. Don’t panic. All you need to know is that a molecule is, in the words of a first-grader of my acquaintance, “one of those eentsy-weentsy things that stuff is made of.” That definition, plus the corollary that different stuff is different because it’s made of different kinds of molecules, will stand you in good stead.)

The sense of smell can detect only gaseous molecules floating around in the air. The sense of taste can detect only molecules dissolved in water, whether in the food’s own liquid or in saliva. (You can’t smell or taste a rock.) As is the case with many other animal species, it is smell that attracts us to food and taste that helps us find edible—and appetizing—foods.

What we call flavor is a combination of odors that our nose detects and tastes that our taste buds detect, with additional contributions from temperature, pungency (the “sting” of spices), and texture (the structure and feel of the food in the mouth). The olfactory receptors in our noses can differentiate among thousands of different odors and contribute an estimated 80 percent of flavor. If this figure appears high, remember that the mouth and nose are connected, so that gaseous molecules released in the mouth by chewing can travel upward into the nasal cavity. Moreover, swallowing creates a partial vacuum in the nasal cavity and draws air up from the mouth into the nose.

Compared with our sense of smell, our sense of taste is relatively dull. Our taste buds are distributed mostly over the tongue, but are also found on the hard palate (the front, bony part of the roof of the mouth) and the soft palate, a flap of soft tissue ending in the uvula, “that little thing hanging down” just before the throat.

Traditionally, it has been thought that there are only four primary tastes: sweet, sour, salty, and bitter, and that we have specialized taste buds for each. Today, it is generally agreed that there is at least one other primary taste, known by its Japanese name,
umami
. It is associated with MSG (monosodium glutamate) and other compounds of glutamic acid, one of the common amino acids that are the building blocks of proteins. Umami is a savory kind of taste associated with protein-rich foods such as meat and cheese. Moreover, it is no longer believed that each taste bud responds exclusively to a single kind of stimulus, but that it may also respond in lesser degrees to others.

Thus, the standard “map of the tongue” in textbooks, illustrating sweet buds at the tip, salty buds on either side of the tip, sour buds along the sides, and bitter buds at the back, is an oversimplification; it shows only the areas where the tongue is most sensitive to the primary tastes. What we actually taste is the overall pattern of stimuli from all the taste receptors, the cells within the taste buds that actually detect the various tastes. The recent success in sequencing the human genome has enabled researchers to identify the probable genes that produce the receptors for bitterness and sweetness, but not yet for the others.

When the combined taste, smell, and textural stimuli reach the brain, they remain to be interpreted. Whether the overall sensation will be pleasant, repulsive, or somewhere in between will depend on individual physiological differences, on previous experience (“just like my mother used to make”), and on cultural habituation (haggis, anyone?).

One taste sensation is undeniably the favorite of our species and of many others in the animal kingdom from hummingbirds to horses: sweetness. To paraphrase a famously ungrammatical advertising slogan, nobody doesn’t like sweetness. Nature undoubtedly set us up for that by making good foods such as ripe fruits taste sweet and poisonous ones, such as those that contain alkaloids, taste bitter. (The alkaloid family of plant chemicals includes such bad actors as morphine, strychnine, and nicotine, not to mention caffeine.)

In our menus, there is only one taste that has an entire course devoted to it: the sweetness of dessert. Appetizers may be savory, main courses may have any complex combination of flavors, but dessert is invariably and sometimes overwhelmingly sweet. We love sweetness so much that we use its concept in terms of endearment (sweetheart, honey) and to describe almost anything or anyone that is particularly pleasant, such as sweet music and a sweet disposition.

When we think of sweetness, we think immediately of sugar. But the word
sugar
does not denote a unique substance; it is a generic term for a whole family of natural chemical compounds that, along with starches, belong to the family of carbohydrates. So before we indulge our sweet tooth—before beginning our scientific repast with dessert—we must see where sugars fit into the scheme of carbohydrates.

FILL ’ER UP

I know that starch and sugar are both carbohydrates, but they’re such different substances. Why are they lumped together in the same category when we talk about nutrition?

I
n a word: fuel. When a runner loads up on “carbs” before a race, it’s like a car filling up at the gas station.

Carbohydrates are a class of natural chemicals that play vital roles in all living things. Both plants and animals manufacture, store, and consume starches and sugars for energy. Cellulose, a complex carbohydrate, makes up the cell walls and structural frameworks of plants—their bones, if you will.

These compounds were named carbohydrates in the early eighteenth century when it was noticed that many of their chemical formulas could be written as if they were made up of carbon atoms (C) plus a number of water molecules (H
₂
O). Thus, the name carbohydrate or “hydrated carbon.” We now know that such a simple formula isn’t true for all carbohydrates, but we’re stuck with the name.

The chemical similarity that unites all carbohydrates is that their molecules all contain glucose, also known as blood sugar. Because of the ubiquity of carbohydrates in plants and animals, glucose is probably the most abundant biological molecule on Earth. Our metabolism breaks all carbohydrates down into glucose, a “simple sugar” (Techspeak: a monosaccharide) that circulates in the blood and provides energy to every cell in the body. Another simple sugar is fructose, found in honey and many fruits.

When two molecules of simple sugars are bonded together, they make a “double sugar” or disaccharide. Sucrose, the sugar in your sugar bowl and in the nectar of your centerpiece’s flowers, is a disaccharide made up of glucose and fructose. Other disaccharides are maltose or malt sugar and lactose or milk sugar, a sugar found only in mammals and never in plants.

Complex carbohydrates or polysaccharides are made up of many simple sugars, often as many as hundreds. That’s where cellulose and the starches fit in. Foods such as peas, beans, grains, and potatoes contain both starch and cellulose. The cellulose isn’t digestible by humans (termites can do it), but it’s important in our diets as fiber. Starches are our chief source of energy, because they break down gradually into hundreds of molecules of glucose. That’s why I said that loading up on carbohydrates is like filling a gas tank with fuel.

As different as all these carbohydrates may be in terms of their molecular structures, they all provide the same amount of energy in our metabolism: about 4 calories per gram. That’s because when you come right down to it, they’re all basically glucose.

Two pure starches that you probably have in your pantry are cornstarch and arrowroot. You don’t need to be told where cornstarch comes from, but have you ever seen an arrowroot? It’s a perennial plant grown in the West Indies, Southeast Asia, Australia, and South Africa for its fleshy underground tubers, which are almost pure starch. The tubers are grated, washed, dried, and ground. The resulting powder is used to thicken sauces, puddings, and desserts. But arrowroot does its thickening job at a lower temperature than cornstarch so it’s best for custards and puddings that contain eggs, because they can easily curdle at higher temperatures.

A RAW DEAL

In a health-food store I saw several kinds of raw sugar. How do they differ from refined sugar?

N
ot as much as you may be led to believe. What health-food stores call raw sugar isn’t raw in the sense that it is completely unrefined. It’s just refined to a lesser degree.

From the dawn of history, honey was virtually the only sweetener known to humans. Sugar cane was grown in India some three thousand years ago, but it didn’t find its way to North Africa and southern Europe until around the eighth century A.D.

Luckily for us, Christopher Columbus’s mother-in-law owned a sugar plantation (I’m not making this up) and, even before he married, he had a job ferrying sugar to Genoa from the cane fields in Madeira. All of which probably gave him the idea of taking some sugar cane to the Caribbean on his second voyage to the New World in 1493. The rest is sweet history. Today, an American eats about forty-five pounds of sugar a year, on the average. Think of it: Empty nine 5-pound bags of sugar onto the kitchen counter and behold your personal quota for the year. Of course, you didn’t get it all from the sugar bowl; sugar is an ingredient in an astounding variety of prepared foods.

The claim is often made that brown sugars and so-called raw sugars are more healthful because they have a higher content of natural materials. It’s true that those materials include a variety of minerals—so does the perfectly natural dirt in the cane field—but they’re nothing you can’t get from dozens of other foods. You’d have to eat a truly unhealthful amount of brown sugar to get your daily mineral requirements that way.

Here’s a quick overview of what goes on at the sugar mill, usually located near the cane fields, and the sugar refinery, which may be located some distance away.

Sugar cane grows in tropical regions as tall, bamboo-like stalks about an inch thick and up to ten feet tall, just right for being chopped down with a machete. At the mill, the cut cane is shredded and pressed by machines. The pressed-out juice is clarified by adding lime and allowing the juice to settle, and then boiled down in a partial vacuum (which lowers its boiling temperature) until it thickens into a syrup, colored brown by concentrated impurities. As the water evaporates, the sugar becomes so concentrated that the liquid can’t hold it anymore; the sugar turns into solid crystals. The wet crystals are then spun in a centrifuge, a perforated drum similar to the drum in your washing machine that flings water out of your laundry during the spin cycle. The syrupy liquid—the molasses—is flung out, leaving wet, brown sugar containing an assortment of yeasts, molds, bacteria, soil, fiber, and other miscellaneous plant and insect debris. That’s the real “raw sugar.” The U.S. Food and Drug Administration (FDA) declares it to be unfit for human consumption.

The raw sugar is then shipped to a refinery, where it is purified by washing, re-dissolving, boiling to re-crystallize it, and centrifuging twice more, making the sugar progressively purer and leaving behind progressively more concentrated molasses, whose dark color and intense flavor are due to all the non-sugar components—sometimes called the “ash”—in the cane juice.

Health-food stores that claim to be selling “raw” or “unrefined” sugar are usually selling turbinado sugar, which is a light brown sugar made by steam-washing, re-crystallizing, and centrifuging raw sugar for the second time. In my book, that’s refining. A similar pale brown, large-grained sugar called demerara sugar is used in Europe as a table sugar. It is made on Mauritius, an island in the Indian Ocean off the coast of Madagascar, from sugar cane grown in rich, volcanic soil.

Jaggery sugar, made in rural India, is a dark brown, turbinado-like sugar made by boiling down the sap of certain palm trees in an open container, so that it boils at a higher temperature than in the partial vacuum of the usual cane sugar refining method. Because of the higher temperature, it develops a strong, fudge-like flavor. The boiling also breaks down some of the sucrose into glucose and fructose, making it sweeter than plain sucrose. Jaggery sugar is often sold pressed into blocks, as are other brown sugars in many parts of the world.

The unique flavor of molasses has been described as earthy, sweet, and almost smoky. The molasses from the first sugar crystallization is light-colored and mildly flavored; it is often used as a table syrup. Molasses from the second crystallization is darker and more robust, usually used in cooking. The last, darkest, and most concentrated molasses, called blackstrap, has a strong, bitter flavor that is an acquired taste.

A cleaned-up piece of raw sugar cane, by the way, can be a real treat. Many people in cane-growing areas, especially children, like to chew on sticks of sugar cane. They’re very fibrous, but the juice is, of course, delicious.

MY SUGAR IS SO REFINED

Why do people say that refined, white sugar is bad?

T
his nonsensical claim is a mystery to me. It seems that some people take the word
refined
as an indication that we humans have somehow defied a law of Nature by having the audacity to remove some undesirable materials from a food before eating it. White sugar is just raw sugar with those other materials removed.

When sugar is refined by three successive crystallizations, everything but pure sucrose is left behind in the molasses. The less-refined, browner sugars from earlier stages in the process are more flavorful because of the traces of molasses that they contain. Whether you use light brown or the slightly stronger-flavored dark brown sugar in a recipe is purely a matter of taste.

Many brown sugars sold today in the supermarket are manufactured by spraying molasses onto refined white sugar, rather than by stopping the refining process in midstream. Domino and C&H brown sugars are still made in the traditional way, however.