What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (39 page)

But in hot water these seven-syllable chemicals (
alkylthiosulfonates
) change into other polysyllabic compounds: propyl and propenyl di- and tri-sulfides and thiophenes. These are among the compounds that give flavor to our garlic and onion soups.

And frying? Don’t ask. Dozens of other chemicals are produced at the high temperatures involved, notably the many aromatic, flavorful, and bitter compounds created by the Maillard browning reactions. (See pp. 296–97.)

Let’s look at what happens to onions as we subject them to more and more aggressive cooking techniques. Garlic behaves in very much the same way.

Dried, raw onions are made up of about 37 percent sugars and 8 percent proteins, so they brown predominantly by the Maillard, or sugar–amino acid, reactions. Yet virtually every chef refers to the browning of onions in a skillet as “caramelizing” them. Perhaps a reason for that can be found by examining the three different stages in the cooking of this uniquely flavored vegetable: sweating, goldenizing (I’ll explain), and frying.

•
 Sweating:
We sweat raw onions by placing them diced or sliced in a sauté pan with a little bit of butter or oil, covering the pan with a circle of parchment or waxed paper (or a cover), and cooking them slowly over very low heat. The heat vaporizes some of the water inside the onion’s cells (onions are 89 percent water). The vapor pressure bursts them and releases their juices, in which the onions then simmer and steam. They turn soft and translucent (another consequence of the broken-down cell structure), but we stop cooking them before any browning takes place. The initial pungent flavor compounds will have been converted to the softer-flavored compounds we associate with onion soup.

•
 Goldenizing:
If instead we cook the onions uncovered, the released cell juices will quickly boil off and the temperature will rise from around 212°F (100°C) to perhaps 300°F (149°C), where the Maillard browning reactions proceed rapidly. The fact that some of the Maillard products are sweet is perhaps one reason that cooks are enticed into using the sugar word
caramelize
for this process. What they really mean, however, is taking the onions only to a soft, golden tan—the color of caramel candies—but stopping short of actually browning them.

In hopes of banishing the use of the word caramelizing for the gentle sautéing of onions, I hereby offer to the world the word
goldenizing
. I realize that
goldenize
has only three syllables to
caramelize
’s four (and for heaven’s sake, people, it’s CAR-a-mel-ize, not CARM-el-ize), but what it may lack in grandeur it more than makes up for in accurate imagery.

•
 Frying:
If we continue cooking beyond that stage, Monsieur Maillard really goes to town and we wind up with honest-to-goodness fried onions, with their intense “browned” flavors.

So goldenize your onions to a pleasing russet hue and a mild, sweet flavor. But you’re not caramelizing them unless you’re one of those people who add a little bit of sugar to hasten the production of color.

May I never again hear or read about “caramelizing” onions or, for that matter, “caramelizing” any other foods that cook up brown. Except sugar.

Note: I know full well that I am fighting a losing battle. No matter what this chemist guy says, chefs will continue to talk about “caramelized” onions, “caramelized” grilled meats, “caramelized”
fond
in the bottom of a sauté pan, and “caramelized” anything else that turns brown when cooked. But I tried, and that makes me feel better. The Great Chemist in the Sky will bless me for it.

I absolutely adore garlic and use it in all its forms: roasted whole heads or cloves, chopped, minced, crushed, or pressed, depending on the dish I’m making. But once in a while I’m stuck at the last minute for a touch of garlic flavor in an almost finished soup or stew or on Italian green beans, so I sprinkle on a little garlic powder. I know it’s frowned upon by gourmets, but emergencies are emergencies. What do you think?

....

I
share your love of garlic. When my foodie wife, Marlene, and I first met for a blind coffee date, she didn’t ask about my religion, politics, or income. Practically her first question was “What do you think of garlic?”

Without hesitation I replied, “Garlic is the closest thing we have to proof of the existence of God.” And we have been cooking happily ever after.

First of all, garlic powder is not a good substitute for fresh garlic because in the process of being dried and powdered, garlic loses a great deal of its volatile flavors. But as you say, emergencies are emergencies. I won’t tell anybody if you don’t. (I use it on popcorn.)

Dried garlic was invented for the same reason as other dried spices and herbs: to preserve a perishable product. At the garlic-powder factories they first break the bulbs down into cloves, smash them, and blow away the papery skins. They then dry the naked cloves, remove any residual skin fragments, and powder the dried material. Much of our garlic powder comes from India and China, where both the raw garlic and the hand labor involved in processing it are relatively cheap.

But obviously, the fresh herb loses a lot of its “charm” in the process, so the dried and powdered product can’t hold a candle to the fresh.

I’ve heard warnings about garlic-infused oil, but I never really got to the bottom of it. My question for you is: Is there any validity to the claims that garlic oil is dangerous?

....

W
e must be careful to distinguish between
garlic oil
, the intrinsic essential oil of the garlic plant,
Allium sativum
, and
garlic-infused oil
, an edible vegetable oil (usually olive oil) that has been flavored with garlic.

Pure garlic oil is indeed nasty stuff that is never ingested
per se
. One of its major ingredients is allyl trisulfide, a teaspoon of which in its pure form would kill half the people who swallowed it and burn the esophagus in the rest of them. But you could never eat enough garlic to come within miles of that amount, nor would anyone come within miles of you if you did.

When chemically pure garlic oil is required for nonfood purposes (it is an effective antibacterial, antifungal, and insecticide), it is obtained, as are most plant essential oils, by steam distillation, in which the crushed plant material is boiled in water. The resulting mixture of steam and vaporized oil is condensed, whereupon the water and the oil settle out as separate layers.

All right, then. So is garlic-infused olive or other vegetable oil dangerous? It depends on how you make it. If you add garlic cloves willy-nilly, unpeeled or peeled, whole or minced, to oil and let it stand for weeks at room temperature, yes, you’re flirting with botulism.

The lethal
Clostridium botulinum
bacterium lives in the soil and in stream and lake sediments, among other places. It cannot flourish in extreme dryness or in air, but will thrive in a moist, airless (anaerobic) environment. And exactly those conditions can exist on the surface of a moist garlic clove smothered in oil.

Many references tell us that
C. botulinum
bacteria can be killed by being heated for 10 minutes at a temperature above 175°F (79°C) or that they can at least be inhibited by acidic media below pH 4.6. That’s true of the active bacteria themselves, but their dormant spores, if present, can survive long periods of highly unfavorable environments such as air, dryness, and high temperatures. In fact, the 175-degree treatment may only “heat-shock” the spores into germinating more readily. The spores are not reliably killed until subjected to a temperature of 250°F (121°C) for several minutes, as is done in commercial canning. At home, that temperature can be reached in either an oven or a pressure cooker. But simple boiling or simmering will
not
do the job.

Executing the bacteria and their spores may be too little and too late, however, because it’s not the bacteria themselves that are the potential killers; it’s a neurotoxin they manufacture while multiplying. Botulinum toxin is one of the most powerful poisons known.

Virtually all references repeat the statement that the toxin is not destroyed by the heat of cooking. But that’s a precautionary oversimplification. The toxin is actually unstable to heat, but it depends on what we mean by “cooking.” Research by several groups of scientists in the 1970s showed that different amounts of toxin, different foods, different pH’s, and different acids can affect the toxin-deactivation process differently. So it is indeed prudent to assume that you can’t get rid of it by “cooking.”

The symptoms of botulin poisoning were named
botulism
when a number of people died in Germany in the late eighteenth century after eating contaminated sausage; the Latin word for sausage is
botulus
. Botulism is a rare occurrence, with only ten to thirty outbreaks per year in the United States, so there is hardly a galloping botulism plague going on. But a head of garlic just
might
have some
C. botulinum
spores lurking under its skin, where they would lie protected from air until they found themselves in an airless medium, such as when submerged in a sea of oil. There, the spores
could
become active and launch a reproductive orgy, even at refrigerator temperatures. It’s the better part of valor, therefore, not to tempt fate by making your own garlic-infused oil. Commercial garlic-infused oil products are usually acidified with vinegar to thwart bacterial growth. But acidifying a solid in an oil can be tricky, so it isn’t recommended for home preparation of garlic-flavored oil.

Still want to make some? Adventurous types should make only a small amount from chopped garlic in olive oil, keep it refrigerated, and discard what isn’t used after a week or two.

Sometimes a recipe will direct that a spice or herb be added at the beginning of cooking, and sometimes only near the end of a long simmer. Does it really matter? If so, why?

....

Y
es, it matters.

The amount of flavor contributed by a spice or herb depends on the amount of essential oil it contains, not on the total amount or weight of the whole substance. Spices and herbs—instead of repeating “spice or herb” eleven more times in this section, may I call them generically “sperbs”? Thank you—sperbs that are powdered or ground give up their oils readily in the heat of cooking because their huge surface areas allow their essential oils to evaporate quickly. Thus, finely divided sperbs should be added near the end, rather than the beginning of cooking, lest all their essential oils evaporate and the kitchen smell better than the food tastes. Whole sperbs on the other hand, such as peppercorns and bay leaves, give up their essences slowly and are added at the beginning.

Because most essential oils are volatile, sperbs lose their effectiveness in storage as the oils slowly evaporate. So fresh sperbs are always more potent than stale ones. Even low levels of heat can slowly drive off the oils, so sperbs also should be stored in a cool location. Ground sperbs lose their strength by evaporation much faster than whole ones.

Nutmeg and black pepper, especially, should always be bought whole and ground on the spot when needed. Hot chili peppers, on the other hand, keep their heat even when dried and ground, because capsaicin, the “hot stuff” in them, is not very volatile. That’s why you can’t tell how hot a pepper is by smelling it.

You’d be surprised at how much of most sperbs’ verve is lost over the period of a year or less, especially if ground. Sniff your sperbs; if you can recall that they smelled much more potent when new, replace them with fresh samples. It’s a good idea to date the labels when you buy them. And check the vividness of their colors periodically. Green, leafy herbs such as tarragon and rosemary fade with age, as do red spices such as Cayenne pepper, paprika, and chili powder.

Some sperb fanatics (sperbivores?) go so far as to keep their sperbs in the freezer. I don’t see why that shouldn’t work.