What Einstein Told His Cook (30 page)

I hereby quote from the April 1, 2000, revision of The U.S. Code of Federal Regulations, Title 27 (Alcohol, Tobacco Products and Firearms), Chapter 1 (Bureau of Alcohol, Tobacco and Firearms, Department of the Treasury), Part 7 (Labeling and Advertising of Malt Beverages), Subpart C (Labeling Requirements for Malt Beverages), Section 7.71 (Alcoholic content), Subsection (a): “Alcoholic content…may be stated on a label unless prohibited by State law.”

Individual states are therefore explicitly allowed to trump federal law if they wish, which is not the case with wine or distilled spirits, over which federal law rules supreme. As you can imagine, state beer-labeling laws now vary all over the lot.

From The Beer Institute I obtained information published in the
Modern Brewery Age Blue Book
, which summarizes the crazy quilt of labeling laws in all fifty states, the District of Columbia, and Puerto Rico.

By my count, about twenty-seven states still prohibit the labeling of alcohol content, four states require the labeling of beers containing less than 3.2 percent alcohol, and the rest either don’t seem to care or have laws that are so complex as to raise questions about the alcoholic content of the legislators. (Minnesota laws win the prize for complexity.) Alaska, as far as I can tell, both prohibits and requires strength labeling.

HOW MUCH IS NONE?

Is there any alcohol at all in a non-alcoholic beer?

T
he U.S. Code of Federal Regulations, Title 27, Chapter 1, part 7, etc., etc., etc. says that “the terms ‘low alcohol’ or ‘reduced alcohol’ may be used only on malt beverages containing less than 2.5 percent alcohol by volume” and that nonalcoholic beer must contain less than 0.5 percent alcohol by volume.

By volume? Yes, by volume. That’s another fairly recent change. Various brewers had been in the habit of expressing alcohol contents as percent by weight: how many grams of alcohol there are in 100 grams of brew. Others had been accustomed to expressing it as percent by volume: how many milliliters of alcohol there are in 100 milliliters of brew. But again, the U.S. Code of Federal Regulations, Title 27, etc. has stepped in: “Statement of alcoholic content shall be expressed in percent alcohol by volume, and not by percent by weight….” That’s good, because the alcoholic contents of wines and distilled beverages are also expressed as percent by volume, so now they’re all consistent.

W
ITH TONGUE FIRMLY PLANTED
in cheek, the British essayist and critic Charles Lamb (1775–1834), in “A Dissertation on Roast Pig,” tells how humans first discovered cooking or, more precisely, roasting, after “for the first seventy thousand ages” eating their meat raw by “clawing or biting it from the living animal.”

The story, purportedly discovered in an ancient Chinese manuscript, tells of the young son of a swineherd, who accidentally set fire to their cottage, which burned to the ground, killing the nine pigs within. (Swineherds apparently lived that way.) Stooping down to touch one of the dead pigs, the son burned his fingers and instinctively put them to his mouth to cool them, whereupon he tasted a delicious flavor never before experienced by mankind.

Recognizing a good thing when they tasted it, the swineherd and his son thenceforth built a series of less and less substantial cottages, burning them down each time with pigs inside to produce the marvelously flavorful meat. Their secret got out, however, and before long everyone in the village was building and burning down flimsy houses with pigs inside. Eventually, “in the process of time a sage arose…who made a discovery, that the flesh of swine, or indeed of any other animal, might be cooked (burnt, as they called it) without the necessity of consuming a whole house to dress it.”

Right up until the beginning of the twentieth century, we humans continued to build fires whenever we wanted to cook. By then we had learned to build the fires on kitchen hearths and later to confine them in enclosures called ovens. Still, every cook had to obtain fuel and set fire to it in order to roast a pig or even to boil water.

But it need not be so.

What if we could build a single, huge fire in a remote location and somehow capture its energy and deliver it, like fresh milk, directly to thousands of kitchens? Well, today we can, through the miracle of electricity.

Only a hundred years ago we discovered how to burn huge quantities of fuel in a central plant, use the fire’s heat to boil water and make steam, use that steam to generate electricity, and then send the electrical energy surging through copper wires for hundreds of miles to thousands of kitchens, in which thousands of cooks could turn it back into heat for roasting, toasting, boiling, broiling, and baking. All from a single fire.

We first used this new form of transmissible fire to replace gas for lighting our streets and parlors (when we had parlors). Then in 1909 electricity moved into the kitchen when General Electric and Westinghouse marketed their first electric toasters. Electric ranges, ovens, and refrigerators followed. Today, we can hardly turn out a meal without our electric ovens, ranges, broilers, beaters, mixers, blenders, food processors, coffeemakers, rice cookers, bread machines, deep fryers, skillets, woks, grills, slow cookers, steamers, waffle irons, slicers, and knives. (I once invented an electric fork to go with the electric knife, but it never caught on.)

Is that the end of humankind’s energy-for-cooking story? It was, until fifty years ago, when a totally new, fireless method of making heat for cooking was invented: the microwave oven. It worked on a brand-new principle that few people understood, and many consequently feared it. Some still fear and mistrust their microwave ovens, which in spite of their omnipresence, remain the most baffling of all home appliances. Yes, it runs on electricity, but it heats food in a never-before-dreamed-of way, without even having to be hot itself. It is the first new way of cooking in more than a million years.

I HAVE PROBABLY RECEIVED
more questions about microwave ovens than about any other subject. What follows are some of the most frequently asked questions. I hope the answers will provide enough understanding of these appliances to enable you to answer your own questions as they arise.

What is a microwave?

There is so much anxiety among home cooks about microwave ovens that you’d think they were kitchen-sized nuclear reactors. The situation is not helped by some authors of food books, who seem not to know the difference between microwaves and radioactivity. Yes, they are both radiations, but so are the television radiations that bring us vapid sitcoms. It’s hard to say which are more to be avoided.

Microwaves are waves of electromagnetic radiation just like radio waves, but of shorter wavelength and higher energy. (Wavelength and energy are related; the shorter the wavelength the higher the energy.) Electromagnetic radiation consists of waves of pure energy, traveling through space at the speed of light. Light itself, in fact, consists of electromagnetic waves of even shorter wavelength and higher energy than microwaves. It’s the specific wavelength and energy of a radiation that gives it its own, specific properties. Thus, you can’t cook food with light (but see page 304) and you can’t read by microwaves.

Microwaves are generated by a kind of vacuum tube called a magnetron, which spews them out into your oven, a sealed metal box in which the microwaves continually bounce around as long as the magnetron is operating. Magnetrons are rated by their microwave power output, which is usually from 600 to 900 watts. (Note that this is the number of watts of microwaves produced, not the number of watts of electricity that the appliance uses, which is higher.)

But that doesn’t tell the whole story. The cooking power of a microwave oven, and hence how fast it will do its chores, depends on the number of watts of microwaves there are per cubic foot of space in the box. To compare ovens, divide the microwave wattage by the number of cubic feet. For example, an 800-watt, 0.8-cubic-foot oven has a relative cooking power of 800 ÷ 0.8 = 1000, which is pretty typical. Because different ovens have different cooking powers, recipes can’t be specific about how long any given microwaving operation should take.

How do microwaves make heat?

Don’t try to find the answer to that question in food books. With only one exception, every book in my food library, including those devoted exclusively to microwave cooking, either evades the question entirely or gives the same misleading answer. Evading the issue only reinforces the less-than-helpful notion of a magic box. But promulgating a wrong answer is even worse.

The ubiquitous nonexplanation is that “microwaves make water molecules rub up against one another, and the resulting friction causes heat.” This misinformation rubs
me
the wrong way, because friction isn’t involved at all. The idea of water molecules rubbing up against one another to make heat is just plain silly. Just try to start a fire by rubbing two pieces of water together. Nevertheless, you’ll find the friction fiction even in some of the instruction manuals that come with the ovens.

Here’s what really happens.

Some of the molecules in food—particularly water molecules—behave like tiny electric magnets. (Techspeak: The molecules are electric dipoles or, in other words, they are polar.) They tend to line up with the direction of an electric field, just as the magnet in a compass tends to line up with Earth’s magnetic field. The microwaves in your oven, which have a frequency of 2.45 gigaHertz or 2.45 billion cycles per second, are producing an electric field that reverses its direction 4.9 billion times a second. The poor little water molecules go absolutely nuts trying to keep up by flipping their orientations back and forth 4.9 billion times a second.

In their agitation, the frenetically flipping, microwave-energized molecules bang up against neighboring molecules and knock them around, sort of like the way in which an exploding kernel of popcorn scatters its neighbors. Once knocked, a formerly stationary molecule becomes a fast-moving molecule, and a fast molecule is by definition a hot molecule. Thus does the microwave-induced molecular flipping get transformed into widespread heat.

Please note that nowhere have I said anything about friction between molecules. Friction, if I may remind you, is the resistance that keeps two solid surfaces from sliding freely over one another. This resistance saps away some of the energy of movement, and that sapped energy has to show up somewhere else, because energy can’t just disappear into nowhere. So it shows up as heat. That’s fine for high-friction rubber tires and even low-friction hockey pucks, but a water molecule doesn’t need to be rubbed by some kind of molecular masseuse to get hot in a microwave oven. All it has to do is get knocked around by a fast-flipping neighbor that has swallowed a microwave.

Oddly, microwave ovens aren’t very good at melting ice. That’s because the water molecules in ice are tied pretty tightly together into a rigid framework (Techspeak: a crystal lattice), so they can’t flip back and forth under the influence of the microwaves’ oscillation, much as they may feel the urge. When you defrost frozen food in your microwave oven, you’re heating mostly the other, non-ice parts of the food, and the resulting heat then flows into the ice crystals and melts them.

Why does microwaved food sometimes have to stand for a while after it’s been heated?

Unlike their electromagnetic cousins the X rays, which are of much higher frequency and energy, microwaves can’t penetrate food more than an inch or so; their energy is completely absorbed and turned into heat within that region. That’s one reason for the “cover and wait” injunction of recipes and “smart” ovens: It takes time for the outer heat to work its way into the food’s interior. In the absence of a bossy oven, a recipe will often tell you to stop and stir the food before continuing the heating. Same reason.

The heat distributes itself in two ways. First, the hottest molecules bounce against adjacent, less-hot molecules in the food, transferring some of their motion—their heat—to them, so that the heat gradually works its way deeper into the food.

Second, much of the water has actually been turned into steam, which then diffuses through the food, giving up its heat along the way. That’s why most microwave heating is done in loosely covered containers; you want to keep that hot steam in, but you don’t want it to build up pressure and pop the lid. Both of these heat-transfer processes are slow, so if the heat isn’t given enough time to distribute itself uniformly, you’ll wind up with hot and cold spots in the food.

Virtually all food contains water, so virtually all food can be heated by microwaves. (Don’t try to cook dried mushrooms, for example.) But the molecules of certain foods other than water, notably fats and sugars, are also heated by microwaves. That’s why bacon cooks so well in the microwave oven, and why the sweet raisins inside a microwave-heated raisin bran muffin can get dangerously, tongue-burning hot, even though the cake part is merely warm.

It therefore pays to be careful with fatty and sugary foods. Very hot water molecules can boil off as steam, but very hot fat and sugar molecules stay in place as unexpected hazards. That’s another reason why it’s always wise to wait a while for the steam to calm down and the hot spots to even out before removing and eating microwaved food.

Why does my microwave oven sound as if it’s going on and off all the time?

Because it is. The magnetron cycles on and off to allow periods of time for the heat to distribute itself through the food. When you set the oven for a percentage of full “power,” what you’re adjusting isn’t the magnetron’s wattage; it can operate only at its full, rated power (but see below). What you’re setting is the percentage of time it’s turned on. “Fifty percent power” means that it’s on half the time. The on-and-off whirring sound is the sound of the magnetron’s cooling fan.

In some of the more sophisticated ovens, various sequences and lengths of on and off periods are programmed into the machine to optimize specific jobs, such as “reheat dinner plate,” “cook baked potato,” “defrost vegetable,” and, most important of all, “popcorn.”

A relatively new development in microwave ovens, however, is “inverter technology.” Instead of cycling on and off, the oven can actually deliver continuous, lower levels of power for more even heating.

Why do microwave ovens cook so much faster than conventional ovens?

Before it can heat the food, a conventional gas or electric oven first has to heat some two to four cubic feet of air (“preheating the oven”), after which the hot air must transfer its heat energy into the food. These are very slow and very inefficient processes. A microwave oven, on the other hand, heats the food—and only the food—by depositing its energy directly into it with no intermediary such as air or water (as in boiling) involved.

The statement found in several microwave cookbooks to the effect that microwaves cook food so quickly “because they are so tiny, they travel quickly” is nonsense. All electromagnetic waves travel at the speed of light, no matter what their wavelength. And the “micro” in microwave doesn’t mean “tiny.” They were named “microwaves” because they are essentially ultra-short radio waves.

Why does the food have to be rotated while cooking?

It’s hard to design a microwave oven in which the intensity of the microwaves is completely uniform throughout the entire volume of the box so that food in all locations will be subjected to the same heating power. Moreover, any food in the oven is sucking up microwaves and upsetting whatever uniformity there might otherwise be. You can buy an inexpensive microwave-sensitive gadget in a kitchenware store, put it in various parts of the oven, and see that it registers different intensities at different locations.