Read What Einstein Kept Under His Hat: Secrets of Science in the Kitchen Online
Authors: Robert L. Wolke
I said “approximate” because there may be other carbohydrates hiding somewhere off the Nutrition Facts charts of many foods—the sugar alcohols, for example, which include glycerol, mannitol, sorbitol, inositol, and xylitol (in fact, anything in the ingredient list ending in -
ol
). They are present in relatively small amounts as sweeteners, but they are metabolized less completely than sugars and therefore contribute fewer calories.
| | THE GRITTY DETAILS | |
Can you straighten out for me all the corn products on the shelves of my supermarket? There are cornmeals labeled yellow or white, coarse or fine, and stone-ground or steel-cut, not to mention cornstarch or the hominy and grits that they like in the South. Which ones do I use for cornbread, for muffins, or for polenta—or does it matter?
....
Y
es, it matters, but mostly in terms of texture, not substance.
They’re all made from that incredibly versatile and internationally esteemed New World grain called corn in the United States and maize—from the Caribbean Taíno Indian word
mahiz
—almost everywhere else.
A kernel of corn is a seed with essentially three parts. The tough, outer hull (the
pericarp
) is made mostly of indigestible cellulose. A body of starchy material (the
endosperm
) nourishes the seed when it sprouts (
germinates
). The life-transmitting embryo (the
germ
) in the middle of the seed is the part that will grow into a new plant when conditions are right for germination. It contains the seed’s main energy supply in the form of oil.
Corn kernels can be processed in dozens of ways to produce an astounding variety of products. One main distinction hinges upon which parts of the kernels are retained. The starchy endosperm is always used, but the outer hull and/or the germ may or may not be removed. What is called cornstarch in the United States and corn flour in the United Kingdom is the dried and finely powdered endosperm alone.
Another main distinction among cornmeal products is the texture, that is, how coarsely or finely the dried kernels have been ground. But the names can be perplexing:
Flour
, of course, is fine, not coarse,
While
meal
is much more coarse, of course.
The meal called “Medium,” of course,
Is coarse, but not as coarse as “Coarse.”
But if the label calls it “Fine,”
It’s
flour
, not
meal,
I would opine.
Historically, of course (
Editor to author
:
NOW CUT THAT OUT!),
dried corn kernels were pulverized between millstones in a waterwheel-powered mill down by the old mill stream. Stone-ground cornmeal, sometimes nostalgically but nonsensically called water-ground cornmeal, is available in many “health-food” stores. It is slightly more nutritious and flavorful than other cornmeals because it retains some of the hull or bran and some of the oil-containing germ. But because of the oil, it is perishable and cannot be stored at room temperature for very long without turning rancid. Refrigerated, it will keep for a couple of months.
Most modern cornmeal is produced by crushing the dried kernels between huge steel rollers, making grains that are more sharply shaped than in the stone-ground meals. The rolled product, referred to as steel-cut, contains only the starchy endosperm with very little hull or germ, and it therefore has a very long shelf life when kept in a cool, sealed container. If your supermarket’s cornmeal isn’t labeled stone-ground or water-ground, it’s steel-cut. (To split a hair, steel-cut cornmeal isn’t cut; it’s steel-crushed.)
After the kernels’ hulls and germs are removed either mechanically or chemically with lime or lye, the endosperm can be washed and dried, at which time it is known as hominy. Then it may be ground or crushed into rather coarse particles to form hominy grits. After their water is restored by boiling, hominy grits can be found on virtually every breakfast plate below the Mason-Dixon Line.
Which product to use for what? Southerners insist that their traditional cornbread be made from stone-ground white cornmeal, either coarse or medium depending on individual preference. Yankees aren’t so fussy, and even go so far as to combine the cornmeal with wheat flour and sugar to make a more breadlike bread, because cornmeal doesn’t contain the gluten that gives bread its elastic texture.
Polenta is generally made with yellow cornmeal of either coarse or fine grind, because the boiled cornmeal softens into a homogeneous mass anyway. And need I point out that yellow cornmeal is made from yellow corn and white cornmeal is made from white corn? (Apologies.)
THE FOODIE’S FICTIONARY:
Hominy—an unknown number, as in “Hominy cooks does it take to spoil the broth?”
| | Polenta Two Ways | |
S
ome home cooks shy away from making polenta because the traditional Italian method (adding cornmeal to boiling water over direct heat with continual stirring) takes too much of the cook’s attention. Your Italian grandmother may be shocked, but there are other ways to make polenta that are easier on the cook. You can make it in a double boiler or in the oven. When the polenta is ready, it will be thick and smooth, with no sign of grittiness.
DOUBLE-BOILER POLENTA:
4 cups water
1 teaspoon salt
1 cup yellow cornmeal, coarse or fine
Butter to taste
1.
Bring 2
1
/
2
cups of the water to a boil in the top part of a double boiler over direct heat. Add the salt.
2.
In a medium bowl, mix the cornmeal with the remaining 1
1
/
2
cups water. Add the mixture to the boiling water and stir well. Reduce the heat to medium and cook, stirring constantly, until the mixture boils.
3.
Place the cornmeal mixture over boiling water in the bottom part of the double boiler. Cover and cook, stirring occasionally, for about 45 minutes, or until smooth and thick. Stir in butter to taste.
MAKES ABOUT 4 CUPS, OR 4 SERVINGS
BAKED POLENTA:
2 tablespoons olive oil
2 cups yellow cornmeal
6
1
/
2
cups water
1
1
/
2
teaspoons salt
1.
Preheat the oven to 400°F. Grease a 9-by-13-inch baking pan.
2.
In a large bowl, mix together the olive oil, cornmeal, water, and salt.
3.
Transfer the mixture to the baking pan. Carefully place the pan in the oven. (It will want to slosh over.)
4.
Bake uncovered for 45 minutes. With a fork or a wooden spoon, stir the polenta until evenly combined and smooth. Bake for 5 minutes longer, or until slightly puffy.
MAKES ABOUT 8 CUPS, OR 8 SERVINGS
VARIATIONS ON THE THEME
Polenta with Gorgonzola
: Spoon soft, cooked polenta into a warmed serving dish. Make a well in the center and fill it with, say, 3 tablespoons unsalted butter and 3 ounces crumbled Gorgonzola cheese. Amounts will vary according to the amount of polenta you have made. Spoon some of the butter and cheese onto each serving of polenta.
Broiled Polenta Slices:
Spoon soft, cooked polenta into a greased 9-inch square pan. Spread to make a layer about 1/2 inch thick. Chill. Turn the polenta out of the pan onto a work surface, and cut into squares or rectangles. Place the pieces on a greased cookie sheet. Brush with melted butter and broil, turning once, until browned and crisp on both sides.
Leftover Polenta:
Spoon soft, cooked polenta into a greased loaf pan. Smooth the surface with a wooden spoon, cover with plastic wrap, and refrigerate. Cold polenta, sometimes called mush, is delicious for breakfast. Cut into slices, fry in butter or bacon fat, and top with maple syrup.
| | TORTILLA TIPS | |
My local market sells two types of Mexican tortillas: flour and corn. I assume that the flour tortillas are made out of regular wheat flour. But the corn tortillas are made out of
masa harina
, which, I’m told, is a kind of flour made from corn. Can you tell me how it’s made? And why is lime listed among the ingredients?
....
Y
ou’re correct about the flour tortillas, which should rightly be called wheat flour tortillas, because there are many other kinds of flour made from a wide variety of grains, including barley, rye, and rice. But you’ll rarely find flour tortillas south of the border. In Mexico tortillas are made from corn. Flour tortillas are a Tex-Mex invention.
The word
flour
evolved from
flower
, as used metaphorically to mean the best part of something, such as the flower of a plant or, in culinary use, the best part of a cereal grain. The supposedly inferior parts, the chaff and bran of the wheat berry and the hull of the corn kernel, have presumably been disposed of. To complicate matters, however, the literal translation of the Spanish
masa harina
is “flour dough,” with no specification of the kind of flour. On corn tortillas you may also see the more explicit
harina de maíz
, which distinguishes corn flour from
harina de trigo
, or wheat flour.
Spanish class dismissed.
The cellulose hulls of corn kernels can be loosened and the germs released by being soaked in water containing an alkali. Acids can be powerful chemicals, but so can alkalis. One exceedingly strong alkali is sodium hydroxide (NaOH), also known as caustic soda or lye. It’s so powerful that we use it to unclog drains—it actually dissolves hair and grease. (It turns the grease into soap, but that’s in Chemistry 102.)
In Mexico, the corn kernels are treated with lime, which is much milder than lye but still strong enough to open the cellulose husks of the corn kernels and uncover the starchy endosperm. Lime has been used for this purpose for thousands of years in Mexico and Central America. The husked kernels are then washed, dried, and ground or pounded into
masa
(dough).
Small balls of the dough are flattened into very thin, almost perfect disks by the astoundingly dexterous hands of Mexican women, then baked on a hot griddle for 30 to 60 seconds on each side, and distributed still warm and fresh to lucky local Mexicans, who have never had to deal with the factory-produced, machine-rolled-and-stamped-out, imitations that we gringos must often settle for. The main problem with these commercial pretenders is that a fresh corn tortilla should contain about 40 percent moisture, which is almost impossible to maintain during the packaging, freezing, and shipping of the mechanized version.
Sidebar Science:
Lime in the limelight
LIMESTONE,
seashells, coral, chalk, marble, eggshells, pearls, stalactites, and stalagmites all consist mainly of a remarkably versatile and plentiful chemical compound called calcium carbonate (CaCO
3
). It constitutes about 7 percent of our planet’s crust, the 20-mile-or-so-thick top layer. When heated to 1520 to 1650°F (825 to 900°C), calcium carbonate decomposes into carbon dioxide gas (CO2) and calcium oxide or lime (CaO). Lime has been used for centuries to make mortar, glass, and many other useful materials.
When lime is added to water, it forms calcium hydroxide, Ca(OH)
2
, also known as limewater or slaked lime. It is quite alkaline, but not as much so as lye.
The Aztecs used an even more easily obtained alkaline material to treat their corn: wood ashes. All plant materials, including wood, contain potassium (it’s the “potash” in fertilizers), and when they are burned, their ashes are rich in the alkaline chemical potassium carbonate.
The Aztecs didn’t know all that, because Chemistry 101 wasn’t scheduled to be taught for another five hundred years. We can only guess at why they started boiling their corn in water containing wood ashes.
| | HELLO, SUGAR! | |
I’m amazed at how many prepared foods list sugar among their ingredients. Do the manufacturers think the only way to make something taste good is to make it sweet?
....
T
he fact that everybody likes sugar certainly has a lot to do with its presence in so many processed foods. Some breakfast cereals, for example, will surprise you with their content of sugar, if you figure it out. To check your cereals (or other manufactured foods) for sugar content, look at the Nurtrition Facts table and divide the number of grams of sugars per serving by the number of grams of cereal (or other manufactured food) per serving and multiply by 100. You’ll find, for example, that Kellogg’s Raisin Bran is 30 percent sugar by weight and Multi-Bran Chex is 21 percent sugar.
Note that the Nutrition Facts table lists “sugars,” in the plural. That means not only the sucrose from sugar cane (listed as “sugar” among the ingredients) but also sugars present naturally in the food, such as the lactose in milk, the fructose in fruit (such as the raisins in Raisin Bran), and the glucose, maltose, and fructose in any corn sweeteners that may be present. So in addition to sugar (sucrose), look for such ingredients as fructose, maltose, lactose, honey, corn syrup, high-fructose corn syrup, molasses, and fruit-juice concentrate. And note that “evaporated cane juice” is a sneaky euphemism used by “health-food” purveyors to avoid the dreaded
s
-word on their labels. Evaporated sugar-cane juice is, of course, nothing but sugar.