What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (19 page)
Read What Einstein Kept Under His Hat: Secrets of Science in the Kitchen Online
Authors: Robert L. Wolke
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If there are any remaining unpleasant odors, the oil is deodorized by steam distillation under vacuum. The vacuum (actually, just a low air pressure) lowers the boiling point of water and hence the temperature of the steam, so that the oil isn’t subjected to a damagingly high temperature. This process also removes any residual pesticides and other chemicals that may have been used on the oil-bearing plants.
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Finally, an oil may be “fractionated,” “dewaxed,” or “winterized” by being cooled and having any fat fractions that freeze filtered off, so that the oil won’t get cloudy if stored in a cool location. Note that if you keep your expensive extra-virgin olive oil in the refrigerator to delay rancidity—some experts may disagree, but I believe this does no harm—and it turns cloudy, there is nothing wrong with it. The oil will clear up as the solidified fat components melt again when restored to room temperature.
Is all this processing bad for us? You can call it processing or you can call it purification. “Processing” is a bad word these days in some circles, where any intervention by humans or their technology between nature and nourishment is considered unnatural and probably unsafe. But in the case of seed oils such as sunflower, safflower, canola, and peanut, the pressed or extracted crude oils contain many impurities that would affect the flavor, color, and cooking properties if not removed. These include seed fragments, pesticide residues, trace metals, phosphorus, wax, free fatty acids, chlorophyll, carotenoids, and other pigments and odors. If machinery and chemistry weren’t being used to purify our vegetable oils, I doubt that we would find them palatable or in most cases even edible.
In short, “refined” means “purified.” So what’s bad about that?
But note that olive oil is a unique case. Coming as it does from the flesh, rather than the seeds, of the fruit, it’s pure fruit juice that can be consumed just as it comes from the press. Some of the best extra-virgin olive oils, in fact, are bottled without even being filtered.
THE FOODIE’S FICTIONARY:
Palm oil—a bribe
| | Beignets Soufflés | |
V
irtually any cooking oil can be used for deep-frying, a wonderful cooking method for crisping and browning the outer surfaces of foods while leaving them moist and succulent inside.
The first time Bob realized that deep-frying could be used for desserts and pastries other than doughnuts was as a (relatively) young man visiting friends in Belgium and being treated to fruit beignets—inch-or-so chunks of fruit (almost any kind) dipped in a flour-and-beer batter (ah, that Belgian beer!), deep-fried, and dusted with confectioners’ sugar just before serving.
This is the deep-fried dessert to make if you have no fear of frying but a fear of yeast dough.
Pâte à choux
, or cream-puff dough, is one of the easiest, most risk-free doughs in the pastry cook’s repertoire. But instead of being dropped onto a baking sheet to make cream puffs, this soft dough is dropped into hot fat, where it swells, puffs, and browns.
To serve, pour a pool of fresh or bottled fruit syrup onto a dessert plate and top it with three sugared beignets.
1
/
2
cup water
4 tablespoons (
1
/
2
stick) unsalted butter, at room
temperature
Pinch of salt
1
/
2
cup all-purpose flour
2 large eggs, at room temperature
1
/
8
teaspoon orange oil or 1 tablespoon dark rum, optional
Vegetable oil for deep-frying
Confectioners’ sugar for dusting
1.
Combine the water, butter, and salt in a medium saucepan and bring to a boil. Remove from the heat and add the flour all at once. Stir vigorously until the mixture leaves the sides of the pan and forms a ball around the spoon. (If a ball does not form almost immediately, place the saucepan over low heat and beat briskly for a few seconds.) Let the dough cool slightly.
2.
Add the eggs one at a time, beating vigorously until the paste is smooth and glossy before adding the second egg. Add the optional flavoring and beat again.
3.
Add the oil to a wok, heavy skillet, or deep fryer to a depth of about 11/2 inches. Heat the oil to 365°F. It’s a good idea to fry just 1 beignet at first to determine the approximate cooking time, so drop in a tablespoon of dough and fry it before you proceed with frying the rest.
4.
Working in batches, drop the dough by tablespoons into the hot oil. Fry, turning as needed, until browned on all sides and the center is cooked through, about 2 minutes per side. Drain on paper towels.
5.
Serve hot, dusted with confectioners’ sugar.
MAKES ABOUT 20 GOLF BALL–SIZED BEIGNETS
VARIATION: BAKED BEIGNETS SOUFFLÉS
If you have a fear of frying, you can bake beignets using the same dough.
Preheat the oven to 375°F. Place large rounded tablespoons of the dough on an ungreased cookie sheet, spacing them 2 inches apart. Bake for 30 minutes, or until the puffs are golden. When the puffs are cool enough to handle, carefully slice off the tops, their lids, and scoop out the unbaked dough at the centers. Let cool on a wire rack.
To serve, fill with ice cream, sweetened whipped cream, or vanilla pudding. Replace the lids and dust the puffs with confectioners’ sugar before serving.
MAKES ABOUT FOURTEEN 2-INCH PUFFS
| | TRANS FATS TRANS-LATED | |
I’m confused about trans fats. I recently read that hydrogenated, partially hydrogenated, and fractionated oils are considered trans fats. I then bought a tub margarine from our local Whole Foods Market which advertised that it contained no trans fats. However, on closer inspection of the label, I noticed that it contained fractionated oil. So . . . here are my questions. Are fractionated oils considered to be trans fats? What is the difference between fractionated and hydrogenated oil? And what does the “partially” add to the mix?
....
T
here is a lot of confusion surrounding trans fatty acids or “trans fats.” And may I say, if you will accept the compliment, that your degree of confusion is one of the most thorough that I have seen.
The public’s concern about trans fatty acids was heightened on July 11, 2003, when the FDA issued its final rule on the labeling of foods containing trans fatty acids, to wit: “In this final rule and given the current state of scientific knowledge, the FDA is requiring the mandatory declaration in the nutrition label of the amount of trans fatty acids present in foods, including dietary supplements.” (Note that this new labeling is both “required” and “mandatory.” I wouldn’t be surprised if it were also compulsory and obligatory.) The rule was scheduled to become effective on January 1, 2006, some thirteen years after the Center for Science in the Public Interest first blew the whistle on the dangers of trans fatty acids. It’s good to know that our government agencies are on their toes.
Today, one can hardly walk down the street without hearing people asking one another, “What the heck
is
a trans fatty acid, anyway?” That’s why I’m here.
Being a mere Ph.D., not an M.D. (“not a
real
doctor,” as an aunt of mine used to point out at every opportunity), I don’t consider it my shtick to go into the health consequences of ingesting trans fatty acids, except to say that trans fatty acids appear to raise your total blood cholesterol level, raise your LDL or bad cholesterol level, lower your HDL or good cholesterol level, contribute to obesity and diabetes, and according to O.J. are the
real
killers of his ex-wife.
No, just kidding about O.J.
Trans fatty acids (I’ll call them “trans FA’s” from here on) don’t occur naturally, except for small amounts in a few plants such as pomegranates, cabbage, and peas and making up about 3 to 5 percent of the fatty acids in the meat and milk of ruminants: cows, sheep, and goats. They are created in much larger amounts during the artificial hydrogenation of vegetable oils to make them more solid, most often to convert liquid soybean oil into manageably spreadable margarines. In fact, trans FA’s are in every food that says “partially hydrogenated vegetable [or the name of a specific vegetable] oil” in the list of ingredients on the label. And you can assume that virtually everything on the snack-food shelves of your local convenience store is loaded with trans FA’s.
Understanding trans FA’s requires digesting a bit of chemistry. I have set this information aside in “Kinky molecules” on page 169. You may think of it as what the textbooks call Further Reading, which of course nobody reads. Read it or not; it’s your call.
A no-trans tip
The softer a margarine is, the less it has been hydrogenated and the less trans fatty acid it will contain. But I don’t like soft, almost liquid margarines; I like them to have some firmness for spreading on my toast. So I buy a soft, no-trans-fat margarine (according to the label) and keep it in the freezer, where it firms up to a perfect spreading consistency.
With or without the FDA’s required, mandatory, compulsory, and obligatory labeling, how can you tell where all the trans FA’s are hiding? You’re not going to like this, but partially hydrogenated fats carrying their burden of trans FA’s lurk in virtually everything you love to eat: margarine, commercial cakes and cookies, doughnuts, potato chips, crackers, popcorn, nondairy creamers, whipped toppings, gravy mixes, cake mixes, frozen French fries and pizzas, fish sticks, and virtually all commercially fried foods.
Restaurants that brag about using only “pure vegetable oil” don’t tell you that it may contain as much as 40 percent trans FA’s. Peek into the kitchen and you may see that before it was melted it was delivered as a semisolid, like Crisco. That’s the tip-off that it has been hydrogenated—had hydrogen gas forced into it at a high temperature and pressure. (Unless that bucket of white fat is lard, which is another whole story.) To make matters worse, trans FA’s are formed in small amounts at the high temperatures of frying, so you may even be producing them yourself at home.
There is, however, a ray of hope. The amount of trans FA’s formed in the hydrogenation of oils depends on the temperature, the hydrogen gas pressure, the length of exposure, and many other factors. Now that the pressure is on from the feds, you can bet your Twinkie that packaged-food manufacturers have been scrambling to find ways of attaining the desired physical characteristics in their fats with the minimum production of trans FA’s. They want to earn the right to put the coveted phrase “Contains no trans fatty acids” or “Contains no trans fats” on their labels.
But note that “no trans fatty acids” on a label doesn’t mean NO trans fatty acids. According to FDA labeling regulations, it means less than 0.5 gram per serving. Insisting that there not be a single molecule of trans fatty acid in a food would be both unrealistic and unenforceable. There has to be some upper-limit definition of “none.”
Oh, and about fractionated oils: Not to worry. Fractionation has nothing to do with trans FA’s. All it does is remove some of the more saturated, higher-melting fats to keep the product from thickening or freezing when stored in a cool place.
Sidebar Science:
Kinky molecules
A MOLECULE
of any fat (a
triglyceride
) contains three fatty acid molecules attached to a glycerol (glycerin) base. The three fatty acids can be any combination of saturated, monounsaturated, or polyunsaturated. The health consequences of any given fat are purely those of the fatty acids (I’ll call them FA’s from here on) it contains.
The FA parts consist almost entirely of long chains of carbon atoms with hydrogen atoms sticking out like hairs on a caterpillar. In a molecule of a saturated FA, every carbon atom in the chain carries two hydrogen atoms, so the chains look like this: –CH
2
–CH
2
–CH
2
–CH
2
–, etc. (C represents a carbon atom, H represents a hydrogen atom, and — represents a chemical bond between carbon atoms.)
But in an unsaturated FA, there are occasional locations where two adjacent carbon atoms have only one hydrogen atom apiece, and the chain looks like this: –CH
2
–CH
5
CH–CH
2
–, etc. The two middle carbon atoms have squandered twice as much of their available bonding power just between themselves, with none left over for grabbing another two hydrogen atoms. That kind of connection between carbon atoms is called a double bond, indicated by
5
. If there is one such location in a FA molecule, it is said to be monounsaturated; two or more make it a polyunsaturated FA.
Wherever a double bond occurs in an unsaturated FA, it makes a kink or bend in the otherwise straight chain. Kinky molecules can’t pack together as closely as straight molecules can, so the molecules are looser and an unsaturated fat tends to be a runny liquid rather than a firm, compact solid.
But even more significant than the physical properties of the fat is the fact that in most biological processes the exact shapes of molecules can be enormously important. As we metabolize them, it is primarily their different shapes that make kinky, unsaturated FA molecules more healthful than straight, saturated ones.
Food manufacturers want to convert unsaturated liquid fats into semisolid, consumer-friendly fats. So by applying high hydrogen gas pressure and heat—up to 150 psi (10 atmospheres) and 430°F (220°C)—they force two more hydrogen atoms into the double bonds. That is, they
hydrogenate
the unsaturated FA’s to make them more saturated. But if they were to saturate every double bond in a polyunsaturated FA, it would become so hard that it would be as inedible as candle wax.
That’s why liquid vegetable oils are only partially hydrogenated—that is, only a fraction of their double bonds are filled in with hydrogen atoms. Moreover, the hydrogenation process is inherently inefficient, so complete hydrogenation would be difficult to achieve anyway.
But here’s where the trans FA’s come in. During the course of hydrogenation, some of the double bonds evade the addition of two more hydrogen atoms by skipping off to another part of the chain. (The double bond
migrates
.) In the process, their original two hydrogen atoms, circled in the illustrations, which may have been on the same side of the double bond—in a
cis
configuration
—are likely to flip to opposite sides—into a
trans
configuration. This hydrogen-atom-flipping can take place even without double-bond migration, because the trans form is inherently more stable than the cis form. (
Cis
, pronounced “sis,” and
trans
are from the Latin, meaning “on this side” and “across,” respectively.)
So what if the hydrogen atoms
do
switch from the cis to the trans positions? Well, the two different resulting molecules (the two so-called
isomers
) have the same number of atoms of each kind, but they have different shapes. The cis molecules retain the original kinky shape of a normal unsaturated FA. But the newly formed trans molecules are straighter, more resembling a saturated FA.
And that’s the problem. We all know that saturated FA’s are cholesterol-boosting villains, and so then are the similarly shaped trans FA’s. The body treats them as a type of saturated FA, with all its negative health implications—and more.
Note that trans FA’s still have some double bonds, so they are included as unsaturated FA’s in the Nutrition Facts charts on food labels. By the time you read this, however, the FDA may be requiring the amounts of trans FA’s to be stated separately.
