What Einstein Told His Cook (14 page)

The Japanese long ago invented a word to describe the unique effects of seaweed’s glutamates on taste:
umami
. Today,
umami
is acknowledged to represent a separate family of savory tastes that are stimulated by glutamates, similar to the family of sweet tastes that are stimulated by sugar, aspartame, and their saccharine relatives.

Many proteins contain glutamic acid, which can be broken down into free glutamate in several ways, including bacterial fermentation and our own digestion. (There are about four pounds of glutamate in the proteins of the human body.) The chemical breakdown reaction is called hydrolysis, so any time you see “hydrolyzed protein” of any kind—vegetable, soy, or yeast—on a food label, it probably contains free glutamate. Hydrolyzed proteins are the most widely used flavor boosters in prepared foods.

While a food product may not contain MSG as such and may even say “No MSG” on the label, it may well contain other glutamates. So if you suspect that you are one of the small number of people who are hypersensitive to glutamates, watch also for these euphemisms on the labels of soups, vegetables, and snacks: hydrolyzed vegetable protein, autolyzed yeast protein, yeast extract, yeast nutrient, and natural flavor or flavoring.

What’s a “natural flavor,” you ask? It’s a substance derived from something in Nature, rather than made from scratch in a laboratory or factory. To be called “natural,” it doesn’t matter how chemically complex or convoluted the processes may be that ultimately isolated the flavor substance, as long as those processes began with something untouched by human hands.

As The U.S. Code of Federal Regulations 101.22(a)(3) puts it: “The term natural flavor or natural flavoring means the essential oil, oleoresin, essence or extractive, protein hydrolysate, distillate, or any product of roasting, heating or enzymolysis, which contains the flavoring constituents derived from a spice, fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, seafood, poultry, eggs, dairy products, or fermentation products thereof, whose significant function in food is flavoring rather than nutritional. Natural flavors include the natural essence or extractives obtained from plants listed in Secs. 182.10, 182.20, 182.40, and 182.50 and part 184 of this chapter, and the substances listed in Sec. 172.510 of this chapter.”

Got that?

NEW MATH: ZERO
0

Why does the label on my cream cheese package say it contains no calcium? After all, it’s made from milk, isn’t it?

I
f you’ll pardon the double negative, cream cheese doesn’t contain” no calcium. In the jabberwocky world of food labeling, zero is not the same as none.

When you come right down to it, there’s no such thing as a zero amount of anything. All anyone can say is that the amount of something is too small to be detected by whatever detection method is being used. If you can’t find any of a certain substance, that doesn’t mean that there aren’t a couple of zillion molecules of it lurking somewhere below your sensitivity threshold.

With that fundamental principle in mind, the FDA was faced with the problem of what upper limits to place on certain ingredients before allowing food producers to claim in the labels’ Nutrition Facts chart that a food contains “none” or “0 percent,” or is “not a significant source” of a given nutrient. It wasn’t an easy task, especially for such loaded questions as when a food may claim to be “fat-free.” (I’m always amused when a label says “97 percent fat-free” instead of “3 percent fat.”)

Cream cheese is a particularly interesting case, because its calcium content falls right smack on the edge of “zero.”

First of all, being made as it is from cream or a blend of milk and cream, the cheese contains less calcium than you might think. The surprising reason for this is that cream contains substantially less calcium than an equal weight of milk. In the same 100 grams, whole milk contains an average of 119 milligrams of calcium, whereas heavy cream contains only 65. That’s because milk is less fatty and more watery than cream, and most of the calcium resides in the watery parts. It may therefore be left largely behind in the watery whey when the cheese curds are coagulated. That’s especially true of cream cheese, whose whey is relatively acidic (Techspeak: pH 4.6–4.7) and can therefore retain more calcium.

As a result, cream cheese winds up with only 23 milligrams of calcium per ounce compared, for example, with the 147 milligrams in an ounce of mozzarella. Even 23 milligrams is still
some
calcium, of course, not none. So how come it’s listed on the label as “0 percent”?

Pay attention, now, because here’s where it gets a bit complicated. The percentage of a nutrient that’s listed in the Nutrition Facts chart is not the percentage of that nutrient in the product; it’s the percentage of the Reference Daily Intake or RDI for that nutrient. The RDI, which used to be called the Recommended Daily Allowance or RDA and now often appears on the labels as Percent Daily Value or % DV (got it?), is the percentage of a person’s recommended daily intake of that nutrient that each serving provides.

For example, according to the label, a two-tablespoon (32-gram) serving of Jif Creamy Peanut Butter supplies 25 percent of your daily value for fat. But that 32-gram serving contains 16 grams of fat, so the product is actually 50 percent fat.

Now back to the cream cheese. The RDI for calcium is a whopping 1,000 milligrams, so the 23 milligrams of calcium in an ounce of cream cheese is only about 2 percent of the RDI. And guess what? The FDA permits an amount of 2 percent or less per serving to be listed as “0 percent.”

The moral of the story:

FOILED AGAIN

A
s you feared, your lasagne is actually eating holes in the metal. (No reflection on your cooking.) Aluminum is what chemists call an active metal, easily attacked by acids such as the citric and other organic acids in tomatoes. In fact, you shouldn’t cook tomato sauce or other acidic foods in aluminum pots because they can dissolve enough metal to make them taste metallic. Stomach linings, on the other hand, contain a much stronger acid (hydrochloric) than the acids found in any foods, and are even immune to office coffee.

But in your case, something else was going on besides the simple dissolving of a metal by an acid. It turns out that tomato sauce can eat holes in the aluminum foil covering a leftover container only if the container is made of metal, not glass or plastic. So without even asking you, I know that your leftover lasagne must have been in a stainless steel pan or bowl, right? (Elementary, my dear Watson.)

When aluminum metal is in simultaneous contact with a different metal and an electrical conductor such as tomato sauce (you knew, of course, that tomato sauce conducts electricity, didn’t you?), the combination of the three materials actually constitutes an electric battery. Yes, an honest-to-goodness electric battery. An electrical (more accurately an electrolytic) process, not a simple chemical one, is what chews up the foil. While it would be difficult, not to mention messy, to run your Walkman on lasagne power, it could in principle be done.

Here’s what was going on.

Your stainless steel bowl is, of course, mostly iron. Now, iron atoms hold onto their electrons much more tightly than aluminum atoms hold onto theirs. So if given an opportunity, the iron atoms in the bowl will steal electrons away from the aluminum atoms in the foil. The sauce provides that opportunity by offering a conductive path through which the electrons can get from the aluminum to the iron. But an aluminum atom that has lost electrons is no longer an atom of metallic aluminum; it is an atom of an aluminum compound that is capable of dissolving in the sauce. (Techspeak: The aluminum has been oxidized to an acid-soluble compound.) So what you see is that the aluminum foil has been dissolved only where the sauce makes the aluminum-to-iron transfer of electrons possible.

If the lasagne had been put into a nonmetallic bowl, none of this would have happened because glass and plastics have no desire to suck electrons away from other substances. You’ll have to either take my word for that or sign up for Chemistry 202.

You can test this for yourself. Put a tablespoon or so of tomato sauce (ketchup will do) in each of three bowls—stainless steel, plastic, and glass. Lay a strip of aluminum foil on each blob of sauce, making sure that the foil also makes good contact with the bowl. After a couple of days, you’ll see that the foil in the stainless-steel bowl has been eaten away wherever it touched the sauce, while the foil in the other two bowls will be unchanged.

There are a few practical morals to this story.

First of all, your leftover sauce—and it doesn’t have to be tomato sauce; it can be any acidic sauce such as a wine reduction or one containing lemon juice or vinegar—can be kept in any kind of container and covered with anything you wish. But if it’s in a metal bowl covered with aluminum foil, just make sure that the foil isn’t in contact with the sauce.

Second, don’t hesitate to use those aluminum lasagne pans sold in supermarkets. They’re inexpensive, and disposable, and they work just fine. Even if you cover them with aluminum foil, it’s just aluminum against aluminum; no two different metals, so no electrolytic corrosion.

VINEGAR HAPPENS!

I have read so much about the powers of vinegar for everything from cleaning coffeepots to relieving arthritis pain and promoting weight loss. What’s so special about vinegar?

V
inegar has been known for thousands of years. No one even had to make it in the first place, because it actually makes itself. Wherever there happens to be some sugar or alcohol lying around, vinegar is on the way.

Any chemist will tell you without a moment’s hesitation that vinegar is a solution of acetic acid in water. But we may as well define wine as a solution of alcohol in water. Vinegar is so much more than that. The most popular vinegars are made from grapes (red or white wine vinegar), apples (cider vinegar), malted barley or oats (malt vinegar), and rice (…uh, rice vinegar). All retain chemicals from their sources that give them unique flavors and aromas. Beyond that, there are vinegars that have been deliberately flavored with raspberries, garlic, tarragon, and virtually anything else that can be stuffed into the bottle and allowed to steep for a few weeks.

At the high end of the purity spectrum is the familiar distilled white vinegar, which is indeed nothing but pure 5 percent acetic acid in water and is just as well kept in the laundry as in the kitchen. Having been made from industrial alcohol and purified by distillation, white vinegar contains no fruit, grain, or other flavors.

Finally, there is balsamic vinegar. True balsamic vinegar has been made for almost a thousand years in Italy’s region of Emília-Romagna, and particularly in and near the town of Módena in the province’s Réggio nell’Emília region. There, trebbiano grapes are crushed into
must
(the juice and skins), then fermented and aged in a succession of wooden barrels for at least twelve years and perhaps as many as one hundred. The result is a thick, brown brew with a complex sweet-tart, oaky flavor. It is used in small quantities as a condiment, rather than in the familiar ways in which we use ordinary vinegar.

Unfortunately, no one regulates the printing of the word
balsamic
on a label, and the term is sometimes affixed to small, fancy-shaped bottles of sweetened, caramel-colored vinegar and sold for whatever the traffic will bear. Even if the label on a bottle says
Aceto Balsamico di Módena
, there is no real way of judging what’s inside. As Lynne Rossetto Kasper puts it in her book
The Splendid Table
(William Morrow, 1992), “Buying balsamic vinegar poses all the hazards of Russian roulette” (well, maybe not all) and “price is no indicator of quality.” Her advice: For the real thing, made in Italy by the slow, traditional artisanal method, look for the words
Aceto Balsamico Tradizionale di Módena
or the curiously bilingual
Consortium of Producers of Aceto Balsamico Tradizionale di Réggio-Emília
on the label. And bring your checkbook.