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KITCHEN CHEMISTRY / The science of turning failed attempts into cooking triumphs

Gas jets hiss, metal and glass measures clank. Electricity

crackles. Pots bubble and vapors rise. Formulas are consulted.

Sometimes the only difference between a mad scientist's laboratory and a

home kitchen is an inclination to taste the result. In both places, mistakes

happen.

But who has time for mistakes? When a cook puts the energy and ingredients

into a dish, that cook wants success, not a learning experience.

On the other hand, chemistry happens. Most people go through their daily

activities - tailgating that guy in the VW or breathing, as examples - without

a lot of input into the actual nuts and bolts of internal combustion or

respiration.

But in the kitchen, suddenly, the responsibility is all yours. (Maybe

that's why everyone eats out.) We asked people who should know, about common

pitfalls in cooking. From baking to boiling, it turns out, traps await. But

their advice can help you steer a safe path from stove to table. Not every

tricky chemical encounter is covered here, naturally. For that, consult the

accompanying list of science-centric books.

The Lore of Leavening

A turkey seems to inspire more fear in novices than does a pan of brownies

or muffins, yet baking is the more delicate art.

"With baking, across the board, it's over-leavening that's the problem,"

said Shirley Corriher, author of "CookWise" and the upcoming "BakeWise." Baking

powder and baking soda create gas in the presence of liquid, but if the cook,

or the recipe, adds too much, the batter can't hang on to the bigger bubbles.

"So your muffins are too heavy or they collapse," Corriher said. "And you

say, 'Oh, I need more,' when what you need is less."

You can assess a recipe before you risk it: 1 to 1 1/4 teaspoons of baking

powder or 1/4 teaspoon of baking soda, will perfectly leaven 1 cup of flour,

according to Corriher. Even old standbys can benefit from a leavening check,

she said. When people who have made the same recipe for years correct the

leavening, she said, "they're stunned at how much better the result is." (We

put her theory to the test; see accompanying story.)

So what's the difference between baking soda and baking powder? For one

thing, baking soda is an ingredient of baking powder. Baking soda is used in

recipes that have an acid, such as citrus juice, buttermilk or yogurt, or even

honey or brown sugar, Corriher writes in "CookWise." In combination with the

acid, the soda produces its "liftoff" gas much more quickly and leaves behind a

less soapy aftertaste.

Baking powder contains baking soda and enough of an acidic agent, such as

cream of tartar, to use up all the soda, so the recipe doesn't need additional

acid. ("Double-acting" baking powders are so called because part of their power

is unleashed in the presence of moisture and the rest in the oven's heat.)

Egg whites are another traditional leavening agent: Beaten with a whisk,

the protein stretches and traps millions of tiny air bubbles, which expand in

the heat of the oven, lifting your batter along the way.

The risk, particularly when using an electric mixer, is to push the beating

too far, so the whites become as dry and brittle as an old Styrofoam cooler.

Christopher Kimball, editor of Cook's Illustrated magazine, suggests the

addition of a couple of tablespoons of sugar and 1/4 teaspoon of cream of

tartar for every 4 to 6 egg whites.

"It helps stabilize the foam and retain moisture, and it makes it less

likely to be overbeaten." For savory dishes, use only the cream of tartar.

Instead of beating whites "until stiff," as many recipes direct, know that

slightly underbeaten egg whites rise more in the oven.

And although cold eggs separate more easily, room-temperature whites will

whip up to a greater volume than cold ones. (The surface tension of the whites

is lower at higher temperatures, allowing for more expansion.)

The Tough Questions

Was Tuesday night's steak the texture of anchor rope? Did you produce

another batch of steel-belted chicken breast? You cooked them too long. On the

other hand, if your stew or your ribs were tough, you probably didn't cook them

enough.

Even if you know that an animal's moving parts (legs, necks) are by nature

tougher than those just along for the ride (the tenderloin in hogs and cattle,

say, or the breast in earthbound chickens), those plastic-wrapped packages

still can be a mystery. This enigma often leads to a shopper's picking the

wrong cut, the No. 1 mistake consumers make, according to Sara Reddington,

director of the culinary center of National Cattlemen's Beef Association.

"People will buy what they know," she said. They choose a familiar cut,

"even if they are going to do something else." But say you bought a chuck roast

for your stew or braise, as directed, and when you sit down for dinner, the

family falls silent, to save energy for chewing.

"With tough cuts like stew and shank, people just don't cook it long

enough," Kimball said. "There is no secret to braising," defined as cooking in

a closed pot with a small amount of liquid. "You need to get it to 205 to 210

degrees [internally], where the collagen breaks down. If you cook it long

enough, you achieve that." Collagen is the protein that makes up such sturdy

components as cartilage and the connective tissue that wraps muscle cells into

useful bundles.

Reddington modified Kimball's stance: "The part about connective tissue is

right," she said, "but it is actually a time/temperature ratio. So you can cook

it higher and shorter, or longer and lower, but you need that moist heat."

Only the moisture of braising can conduct enough heat into the meat without

burning the exterior; the dry heat of roasting is reserved for already tender

cuts - tenderloin, rib roasts - that are ready to eat at lower internal

temperatures.

Yeah, what about those tender cuts? How come they get tough? Because it is

no longer a case of undercooked connective tissue (they have very little), but

rather overcooked muscle fibers.

Think of a raw chicken breast or fish fillet, or an egg white: They're

translucent because their coiled proteins remain standoffish individuals,

allowing light to shine through a bit. Once heated, the proteins uncoil, or

"denature," and get tangled up in each other, blocking the light: They start to

appear opaque, what cooks might call "done." Keep the heat on, though, and the

proteins tighten their tangles even more, squeezing out the moisture between

them. The muscle fibers shrink and dry out.

"People absolutely, terribly overcook boneless, skinless chicken breasts,"

Corriher said. She likes to steam hers for 7 minutes and let them stand about 4

minutes before cutting. "If you cut into any piece right after removing from

heat, then you'll see pink and the juice will squirt out," she said. "But let

it stand and the juices migrate ... and are actually reabsorbed by the meat."

Saving the Green Stuff

"Most people overcook vegetables," Corriher said, "except for restaurants,

Chinese included, and they undercook them." She cites one exception, a

California chain that has the cooks blanch vegetables in boiling water briefly

before stir-frying: "They get a beautiful green color."

Green vegetables get their color from chlorophyll. When heated, the

chlorophyll loses its magnesium, which is replaced by hydrogen from the

vegetable's natural acids that have escaped the heat-damaged cells. The result

is "a yucky Army drab," Corriher said.

When boiling vegetables, cooks have about 7 minutes before entering

Drabs-ville. That means they might have to cut big greenies like broccoli

stalks into smaller pieces for thorough cooking and good color.

For those in the cabbage family, like Brussels sprouts, 5 minutes is safer.

Corriher said, "Between 5 and 7 minutes, you get twice as much hydrogen

sulfide," the distinctive, and disgusting, rotten-egg gas.

Adding salt is a good idea, because vegetables get tender about 10 percent

faster in salted water, Corriher said. Older recipes often call for adding

baking soda. That's not a good idea, according to Corriher: Though it will

neutralize the acids that cause dull colors, it also destroys cell walls,

leading to mushiness.

Heat It Up

Almost by definition, cooking involves heat, so there is plenty of

opportunity for error.

For instance, lots of people don't get their skillets hot enough before

starting to saute, according to Kimball. "They're scared of heat and smoke."

Even though most home stovetops can't produce the high heat of a commercial

range, Kimball said that heating the empty skillet for 5 minutes before adding

oil or food will work just fine. (That advice assumes you're using a pan with a

stainless-steel or cast-iron surface. Most nonstick pans can't take the heat,

Kimball said.)

But won't the food just take a little longer to cook at a lower

temperature? Weren't we just all worked up about overcooking? Well, yes. But

without enough heat, foods will just sit there and steam rather than brown,

which is why you're cooking in a skillet. Browning is desirable for all the

caramelized flavors it provides.

As McGee writes, "The chemical reactions involved in caramelization are

very numerous and not very well understood," which lets us off the hook. But

one thing is for sure: High heat is necessary.

It's Not Your Fault, Really

Sure, some home cooks are impatient and ill-informed. And some of us got

that way by relying on untested recipes and assumptions perpetuated by

cookbooks and food writers.

One of Corriher's pet peeves is the instruction common in "flaky piecrust"

recipes: "Blend fat into flour until mixture resembles fine meal."

But, she said, "to get a flaky result, you have to have big pieces of fat,

big enough to act as a spacer a few minutes in the oven so that when it melts,

it creates steam pockets, which lift and separate the flour layers. So you need

at least oatmeal-size pieces of fat." She's also miffed by modern

muffin-baking. "The old cookbooks say 425 degrees, but everybody now does it at

350. There's no way you'll get a peak at 350; it's not hot enough to get an

outside peak while the inside is still juicy and rising." These are little

things, maybe, but they show the recipe's potential to abuse its authority.

"Recipes come in, oh my gosh, in all different shapes, from being written

on a napkin to a typed-out version," said Julia Lee, director of the test

kitchen for Saveur magazine, which has made a specialty of regional recipes,

whether from a Spanish chef or a Louisiana veterinarian.

Her kitchen's job is to preserve recipes' integrity and origins. "We're not

adding our own twist; we're just altering to make it work for home cooks," she

said.

A rule of her writing is to describe how something should look, or what its

texture should be, and only then give a time for how long that stage should

take. Those are cues that cooks should look for in any dish, rather than

relying only on stated cooking times. "Our medium heat might be different than

yours," Lee said.

In that sense, with every new recipe, every kitchen is a test kitchen.

A muffin made with the proper proportion of baking powder to flour (above) will

rise better than one with too much leavening (right): The batter can't hold on

to the excessive bubbles.

Keeping the green: Most green vegetables can tolerate about 7 minutes in

boiling water before they start turning a brownish-greenish, overcooked drab

color. Adding salt to the cooking water helps, because it lets vegetables cook

to tenderness in less time.

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