What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (37 page)

•
 
Lump charcoal:
If wood is heated in the absence of oxygen (a process called destructive distillation), it can’t burn. Instead, it decomposes. First, its water is driven off. Then its carbohydrates (mainly cellulose and lignin) begin to break down into methyl alcohol (therefore known as wood alcohol), acetic acid, acetone, formaldehyde, and many other smokes and gases. Eventually, nothing is left but virtually pure carbon. That’s lump charcoal.

For at least four thousand years, people have been making charcoal from wood for use as a cooking fuel. Contrary to an oft-repeated legend, charcoal was not invented by Henry Ford. Nor, I might add, did he invent wood or fire. (But see below.)

Today’s commercial lump charcoal, still retaining the shapes of the wood chunks it was made from, burns hot and clean, with minimal amounts of smoke. It therefore earns my vote (and the secret ballots of most grilling experts) as the best possible fuel for grilling. There’s no fuel like an old fuel.

•
 
Briquettes:
Briquettes—and I won’t call them charcoal briquettes because they contain so much other stuff besides charcoal—were not invented by Henry Ford either. Fuel briquettes were invented and patented by one Orin F. Stafford, a professor at the University of Oregon. Then Ford, always looking to make a buck, jumped in and built a plant to manufacture briquettes on a grand scale, thereby turning the waste sawdust and wood scraps from his Model T plant into a profitable product.

Originally, briquettes were made from powdered charcoal, compressed and bound with starch. But today they’re not that simple. According to a 2000 publication of the Kingsford Products Company, heir to the Ford Charcoal Company, their briquettes contain wood charcoal, mineral char (a soft, brown coal), mineral carbon (graphite), limestone (to produce that nice coating of white ash), starch (as binder), borax (helps release the briquettes from the molds), sawdust (for easier ignition) and sodium nitrate, which releases oxygen when heated and speeds the burn.

Personally, I would rather not have tar-laden coal, starch, borax, and sawdust burning beneath my steak.

•
 
Gas:
The fuel used in modern gas grills is either methane (natural gas, CH
4
) or propane (C
3
H
8
), whose molecules are made of nothing but carbon atoms and hydrogen atoms. And that’s the difference between charcoal (carbon) and gaseous fuels: the hydrogen atoms. While charcoal burns to produce only carbon dioxide (and some carbon monoxide), methane and propane produce both carbon dioxide and water vapor. Hold a transparent glass dish briefly above a gas flame and you’ll see it fog up with condensed water.

Each molecule of burned propane produces four molecules of water. In a typical 40,000-Btu-per-hour gas grill, that translates to 1
1
/
2
quarts of water being given off per hour. The bottom surface of the meat is thus being steamed, and its temperature cannot get as high as with dry-burning charcoal. No wonder you can’t quite achieve that flavorful, seared brown crust that charcoal produces.

Case closed.

Grilling mavens distinguish between two techniques: direct grilling, where the meat is placed directly above a bed of charcoal, and indirect grilling, where the charcoal pile is off to one side.

In the direct method, the heat reaches the meat by both convection (rising hot air) and radiation (infrared rays). In the indirect method, since the meat isn’t directly above the heat source, the heat reaches the meat predominantly by radiation. (The third heat transmission mechanism, conduction, doesn’t play much of a role in grilling.) The meat therefore doesn’t attain as high a temperature in the indirect method and cooks more slowly. If the cooking apparatus is covered, the rising hot air from the coals is trapped and circulates throughout the enclosure, making it into a sort of convection oven. Throw in a few chips of moistened hardwood and you can smoke the food at the same time.

Whoops! In that last paragraph I have slipped from grilling into barbecuing. That’s easy to do, because the same equipment can be used for both, and few people—including the manufacturers of the equipment—bother to make the verbal distinction.

My neighbors bought a smoker. It looks like a big green egg about three feet high, standing on its narrow end. They use it for cooking meats and fish with smoke, and they have a collection of several different woods that they say have different flavors. How does wood smoke cook and flavor food?

....

N
ot having been a termite in a previous life, I cannot comment on the flavors of the woods themselves. But when we burn them and, in effect, eat their smoke, I do have a few observations.

The proper name of your neighbors’ big green egg is the Big Green Egg. It is one brand of
kamado
, a word derived from the traditional Japanese steamed rice cooker, the
mushikamado
, which in Japanese means, well, steamed rice cooker. A
mushikamado
is a hollow, egg-shaped, fired-clay urn, used by building a wood fire in the bottom and suspending a rice cooker from the lid. The rice not only cooks from the heat but acquires an interesting smoky flavor.

In the early 1960s, an enterprising American pilot named Richard Johnson discovered the
mushikamado
in Japan and decided that with a few modifications it could be used as an American backyard cooker and smoker. After more than forty years, his company, the Kamado Corp., still manufactures them in factories in Sacramento, California, and elsewhere. He owns the trademark Kamado, with a capital
K
, but the Big Green Egg people call their product a kamado with a lowercase
k
.

The Big Green Egg, a device used for smoking, grilling, and barbecuing. It is an adaptation of the Japanese
kamado
. (Courtesy of The Big Green Egg.)

There are dozens of other kinds of smokers on the U.S. market, shaped like oil drums, rectangular iron boxes (“smoker ovens”), or you name it—anything that will collect the smoke from burning chunks or chips of hardwood inside an enclosure containing the food. Smoke fiends have been known to adapt everything from charcoal grills to old refrigerators.

Among everyone’s favorite smoked foods are trout, salmon, beef brisket, pork shoulder, turkey, and even vegetables such as potatoes and tomatoes. The temperature is maintained somewhere between 125 and 220°F (52 and 104°C) for long, slow cooking, both to tenderize tough meats (except for fish, which cooks quickly) and to give the smoke enough time to do its flavoring job. With some precautions, foods can be smoked indoors also, either in the oven or in a special range-top roasting pan designed for the purpose. (Turn off your smoke detector and monitor the process carefully. And don’t forget to rearm the smoke detector when you’re done.)

Note that we are talking here about so-called
hot smoking
. At 125 to 220°F (52 to 104ºC), the foods are not only infused with smoke flavor but also cooked to some extent. Commercial smokehouses also employ so-called
cold smoking
(see p. 354), where the temperature of the food, such as bacon, is not allowed to exceed about 90 to 100°F (32 to 38°C). Liquid smoke (see p. 353) is also often used.

One of the earliest cooking methods devised by humans was to hang meat over a wood fire, burning in the bottom of a pit dug into the ground. The intention was that the fire’s heat would cook the meat, but to twist an aphorism, where there’s fire there’s smoke, and the effects of the smoke were inescapable. Important among these effects—although it was not understood until modern times—is that smoke acts as a preservative by killing decay-producing microorganisms. Eventually, the smoke itself became the desired instrument, and smoking foods, most notably hams, to preserve them became a worldwide practice.

Today, we have efficient distribution of foods from producer to consumer, and long-term preservation isn’t as important as it once was. Moreover, we have refrigeration, which doesn’t kill pathogenic organisms but slows down their growth. So now we can smoke foods at home just because we like the flavor. And, yes, different hardwoods—alder, apple, cherry, hickory, maple, oak, and pecan—do impart different flavors to the food via their smoke. After all, if the woods were so chemically identical that they produced chemically identical smoke, they wouldn’t be different trees. Soft woods such as pine, fir, and spruce are unsuitable for smoking food because they contain too much sap and resin, which produce noxious, sooty smoke.

Now look at the blue flame on your gas cooktop or in your gas grill. The flame produces no smoke at all. That’s because the gas is being fed enough oxygen to burn completely. It is all transformed—almost every molecule of it—into the invisible gaseous products carbon dioxide, carbon monoxide, and water vapor. But when wood or almost any other fuel burns, the burning reactions are rarely complete. Wood is solid, and its molecules don’t all get a chance to mix freely with the oxygen in the air. The oxygen-starved fuel can’t burn completely, and tiny particles of it, half-burned and still solid, are released into the maelstrom of flame and rise along with the gases as a black or gray cloud: smoke.

If we want the maximum amount of smoke from burning pieces of wood, then, we must partially starve it of oxygen. So we’ll soak wood chips in water for an hour or so before heating them to their smoke point, at which time they will smolder away, infusing our food with flavors that can’t be achieved in any other way.

And now for the bad news.

Along the way toward complete combustion—which, remember, wood fuel never achieves—hundreds of intermediate chemicals are formed and go up in the smoke. They include formaldehyde, formic acid, phenols, benzene, quinoline, and many other toxic chemicals, some of which are carcinogenic to boot. Among the worst actors are polycyclic aromatic hydrocarbons (PAH’s), a class that includes the arch-carcinogen benzo[a]pyrene, B[a]P. The flat molecules of B[a]P can slip between the rungs of our DNA molecules’ spiral ladder and, if you’ll pardon the technical jargon, louse them up. That can lead to cancer. The popular and uniquely flavorful mesquite is a resinous wood whose smoke has been reported to be particularly rich in PAH’s.

So what price flavor? The first time I had a steak cooked in Arizona over burning mesquite wood, I was, like, blown away, man! It was awesome! (That was for my younger readers.) I have not, however, persisted in a steady diet of mesquite-grilled steak (or any other kind of steak, for that matter), in spite of the fact that a risk is only a risk, not a certainty. But even if that steak doubled my minute risk of PAH-induced cancer, it was worth it.

On the basis of risk statistics, I ceased my daily ingestion of tobacco smoke more than twenty years ago. On the same basis, however, I see no reason to avoid an occasional hit of smoked salmon.

As Voltaire put it, “Moderation is the pleasure of the wise.”

Chapter Eight

Spice Is the
Variety of Life

....

M
ATCH EACH
of the following spices or condiments with the national cuisine that makes the most use of it.
Answers
are at the bottom of the page. No peeking.

Your score of 7 or better has proven my point: The cuisines of various ethnic, national, and regional cultures can be characterized largely by the ways in which they use spices, herbs, and condiments. Spices do indeed enhance the variety of culinary life around the world.

But what’s the difference between a spice and an herb?

They can both be described as plant-derived food ingredients that yield large amounts of flavor from small amounts of substance. That operational nondistinction is really good enough in most situations, because knowing the characteristic flavors and uses of a spice or herb is far more important to the cook than knowing its botanical niceties. Nevertheless, there is a fairly reliable (though often muddied) technical distinction between herbs and spices.

The word
herb
comes from the Latin
herba
, meaning grass or green blades. To a botanist,
herb
is the term for all the soft, nonwoody parts of plants. In common usage, though, an herb (or in Britain a herb) is any leafy plant material used for its flavor, aroma, or reputed medicinal properties.

Herbs have historically been used not only in cooking but in mystical ceremonies and, allegedly, for healing. Today’s flood of “herbal remedies” and supplements is only the latest incarnation of the age-old snake-oil industry. For some reason, many people believe that if it’s “herbal” it’s “natural” and therefore healthful. (“Here, Mr. Socrates, drink this cup of hemlock tea. It’s an all-natural herbal supplement.”)

The word
spice
, on the other hand, has no scientific standing; it’s a catchall term for any plant material, usually excepting leaves, that adds strong aromas and flavors to foods. The word comes from the Latin
species
, meaning assorted merchandise, originally referring to the commercial goods imported from the Orient, of which spices were an important part. Spices may be roots, rhizomes, barks, seeds, fruits, or flowers, but most often they are seeds. Herbs are usually green and relatively mild, while spices can be brown, black, or red and have more pungent flavors.

Because most spices are native to tropical regions and herbs typically grow in temperate climates, cultural and linguistic differences often complicate the picture. For example, the cilantro plant and its herbal leaves are known by that Spanish name, but its seeds, called coriander in English, are a spice.

It would be nice to think that Nature created all those fragrant and flavorful botanical substances purely for our gastronomic delectation. But who do we
Homo sapiens
think we are, anyway? There must be some other evolutionary reason for plants’ having developed the special chemicals in herbs and spices that so delight us. And there is.

Most plants depend for reproduction on pollination by bees and other insects, whom they must attract by some combination of physical and chemical devices. The perception of flower colors is the major physical enticement, but chemicals are just as important. Many plants have developed fragrant chemicals called
essential oils
(see “Quintessential but not essential,” on p. 330) that are quite volatile, that is, that waft readily off into the air. (It may be noted in passing that flowers and perfumes are often a prelude to human reproduction as well.)

Other plants contain unpleasant-smelling or -tasting chemicals to repel foragers, and yet we humans find them pleasant when used in small amounts to flavor our foods.

Three families of plants provide the lion’s share of our culinary herbs and spices.

•
 The mint family (Lamiaceae) provides us with basil, thyme, marjoram, rosemary, lavender, and catnip.

•
 The parsley family (Apiaceae) gives us anise, dill, coriander, caraway, cumin, poison hemlock (!), and such distinctively flavored vegetables as carrot, celery, parsnip, and fennel.

•
 The mustard family (Brassicaceae) includes radish, horseradish, and many vegetables such as broccoli, Brussels sprouts, cabbage, cauliflower, kale, kohlrabi, turnip, rape, and rutabaga, all of whose leaves have a peppery flavor, although they are not generally used as herbs.

In a class by itself is the genus
Capsicum
, included within the family Solanaceae. Capsicums are the spiciest of all spices. They are the fiery New World hot peppers that, as we shall see, are neither hot in the literal sense nor peppers.

Because there are more than a hundred herbs and spices used around the world to add zest to foods, all I can do here is fly low over the landscape and point out a few notable landmarks. But if there is anything—and I mean
anything
—you want to know about any herb or spice, go to http://www-ang.kfunigraz.ac.at/~katzer/engl/, a multilingual website operated with obvious passion by one Gernot Katzer at the University of Graz in Austria.

I hear a lot about essential oils in everything from spices to skin moisturizers and aromatherapy products. What’s essential about them? Are they like the essential amino acids we must have in our diets?

....

N
o, not at all.

Essential oil
is an unfortunate name. An essential oil is not necessarily an oil in the chemical sense, and may not even feel oily at all. Nor is it “essential” in the sense of being indispensable. Aromatherapy and cosmetic flacks take advantage of this misunderstanding by touting the essential oils in their products as if they were somehow imperatives for health and beauty. The adjective
essential
in the name means simply that the substance is the aromatic essence—the concentrated spirit, if you will—of the plant.

Essential oils can be obtained in pure form by steam distillation (boiling the crushed plant material in water and condensing the mixed oil and water vapors), or by extraction into cold fat (
enfleurage
), hot fat (maceration), or volatile organic solvents that can be evaporated away.

If an essential oil is to affect our senses as a flavor or fragrance, it must consist of small, light molecules (with molecular weights of less than about 300 or 400) that can float through the air and reach our noses. These airborne molecules can enter our upper nasal passages, either directly through the nose or through the back of the mouth when we eat the spice. In the upper nasal passages the molecules lock onto olfactory receptors, which fire nerve cells to generate a smell signal. These signals are interpreted in the cortex of the brain, along with taste signals received from our taste buds, to produce the overall sensation of what we call flavor. Although we habitually localize flavor in the mouth, anywhere between 70 and 85 percent of the flavor of our foods is contributed by our sense of smell.

Many essential oils are chemicals called
terpenes
, a class of unsaturated hydrocarbons. Some examples are menthol in oil of peppermint, limonene in orange and lemon oil, and zingerone, which (no kidding) puts the zing in ginger.

A funny coincidence? No. Our English name
ginger
comes to us via a tortuous path from
singivera
in Pali, the religious language of Buddhism, to the Greek
zingiberi
, the Latin
zingiber
, and the Old English
gingifer
. Hence its species name
Zingiber officinale
and the name of one of its main pungent components, zingerone. Our slang word
zing
, meaning zest, may have a consequential origin.

And before you ask, the distilled alcoholic beverage we call gin has an entirely different origin. Its name comes from its predominant flavoring agent, the juniper berry, called
genever
in Dutch. The beverage was invented “for medicinal purposes” (wink) by a seventeenth-century professor of medicine at the University of Leiden in Holland.

I have always wondered about the words
hot
and
spicy
with reference to the tastes of peppers and other spices. For example, why is black pepper “peppery,” while chili peppers are “hot” and ginger is “spicy”? Are the chemicals that cause these sensations all the same?

....

N
o, those different sensory effects are caused by several different chemical compounds. (See Table 6, p. 336.)

It would be much neater if we had individual descriptive words for each of these sensations, because they are indeed all different. Instead, we apply the words
hot
,
peppery
,
spicy
,
pungent
,
piquant
,
biting
,
zingy
, and
sharp
almost indiscriminately to all. But black pepper, chili peppers, ginger, mustard, horseradish, and wasabi are all distinguishable from one another by their distinctive brands of what I’ll generically call pungency, from the Latin
pungere
, meaning to prick or puncture.

The French
piquer
and the Spanish
picar
, meaning to prick or sting, give us the word
piquancy
, which is often used interchangeably with
pungency
but has the slightly broader connotation of an agreeable tartness or zest. A sauce, for example, may be piquant because of the pungent pepper it contains.