- The Washington Times - Thursday, February 6, 2003

Baking a chocolate-chip cookie is a fairly easy task, but behind the simple recipe for one of America's favorite sweets lies a series of complicated chemical processes.
"If you don't have the right flour or use the right amount of baking powder, you're going to get more than just a tough cookie," says Bonnie Moore, a local chef instructor and president-elect of Women Chefs and Restaurateurs, a national organization that promotes women in the restaurant business.
The cookie also might taste like baking powder or be hard as a rock.
This illustrates that cooking is not just an art, but equally a science, says Shirley Corriher, author of "Cookwise: The Hows & Whys of Successful Cooking With Over 230 Great-Tasting Recipes."
Mrs. Corriher, a biochemist-turned-chef, draws on her knowledge of science whenever she cooks, whether it's in front of a studio audience (which happened last week when she and rapper Snoop Dogg cooked together on ABC's "Jimmy Kimmel Live") or teaching a cooking class.
"I think the science frees you up to be wildly creative with recipes," Mrs. Corriher says. "A knowledge of science saves you hours of failed recipes it's a major aid in cooking."
A trained scientific eye can look at a recipe and tell if it's going to work.
"The most common mistake people make is overleavening," Mrs. Corriher says. "If you see a recipe that calls for four teaspoons of baking powder per cup of flour, you know that it's going to fail."
It's going to fail because the simple formula for leavening is 1 teaspoon of baking powder per cup of flour or a quarter-teaspoon of baking soda per cup of flour.
Baking soda and baking powder produce carbon dioxide when heated, which helps leaven cakes. If there is too much carbon dioxide (which creates bubbles) in relation to other ingredients, such as flour, the bubbles have nothing to grab onto; they just rise to the top of the cake or cookie and pop.
"It's a common misconception that more baking powder will make the cake rise more," Ms. Moore says. "The truth is that too much baking powder makes baked goods collapse."

Yeast is another way to leaven baked goods, especially bread. Yeast, like baking powder or baking soda, produces carbon dioxide, which allows the bread dough to rise.
For a fluffy, airy bread, wheat flour is the best, Mrs. Corriher says, because it's high in the proteins glutenin and gliadin. These two proteins, when mixed with water, grab hold of each other, connecting and forming sheets of gluten. These sheets trap air and gases, produced by yeast.
"This protein structure allows the bread to rise instead of becoming a cracker," Ms. Moore says.
Yeast provides the bubbles, and the gluten holds them in place.
The function of kneading is to allow the yeast cells to spread and divide throughout the dough. As long as the dough is kneaded and oxygen is allowed into it, the yeast will continue to divide and multiply to produce even more carbon dioxide rising even more.
It is possible to overknead, particularly when the kneading is done by electric kneading equipment. When a dough is overkneaded, the protein sheet starts unraveling, which eventually results in a gooey mess.
"But if you're kneading by hand, you don't really have to worry about overkneading," Mrs. Corriher says. Plus, the added benefit of kneading by hand is it's so relaxing.

Food science is never as obviously and painfully present as when an onion is sliced.
"When you cut the onion, you rupture its sulfurous contents, and you create this new molecule, ilyl sulfate, which irritates your eyes," says Lisa Lachenmayr, a nutritionist with the University of Maryland College of Agriculture and Natural Resources Cooperative Extension.
There are ways around the onion-induced shedding of tears.
"You can rinse the onion with water, which helps," Ms. Lachenmayr says.
You also can slice the onion in half and put the cut side down on the cutting board, Mrs. Corriher suggests. She adds that the emitting of the eye irritant is a way for onions to protect themselves against predators, much like roses and their thorns.
"Onions can't respond by running away, so they resort to chemical warfare," Mrs. Corriher says.
Though onions can be difficult to deal with in peeling and cutting, they are much easier to store than many other vegetables and fruits, and they last much longer.
"Storing vegetables correctly is important because vegetables actually breathe," Mrs. Corriher says.
Fruits and vegetables take in oxygen, which their cells use for metabolism. In plants, this is called respiration, Mrs. Corriher says. The key to preserving produce is to slow this metabolic process, or respiration.
"So, we have to be cruel and cut off their oxygen," Mrs. Corriher says. "I recommend putting the lettuce in a heavy-duty zip-top bag. That way it can last in your refrigerator for up to a month."
Different vegetables have different rates of metabolism. While lettuce breathes a lot and quickly, potatoes are slow.
Another important aspect of storing food is cooling it properly, Ms. Lachenmayr says. The longer something stays warm, the longer bacteria continues to multiply in the dish.
Warm foods should be put in small containers to cool off quicker and reach 40 degrees Fahrenheit the recommended refrigeration temperature as soon as possible.
"If you have a big pot of chili, it can take up to 24 hours for it to cool down sufficiently," Ms. Lachenmayr says. "It's better to put it in several smaller containers."

Once upon a time, fat was a chef's best friend because of its flavor and smooth consistency. Now, chefs have to work around people's wishes to slash fat. It's not as easy as substituting skim milk for cream, Mrs. Corriher says.
A heavy cream is high in fat and low in protein, which means the fat can coat and separate the proteins, preventing them from joining each other to create curds.
Using cornstarch is one way to prevent curdling when using a lower-fat dairy product, Mrs. Corriher says.
Another way to prevent curdling is to make sure ingredients are mixed in the right sequence, Ms. Lachenmayr says. If something acidic, such as tomato soup, is to be combined with low-fat milk, it's better to add the acidic ingredient gradually to the milk rather than vice versa.
"The protein casing in the milk is extremely sensitive to acid," Ms. Lachenmayr says. "The molecules lose their charge, and then they adhere together, and curdling starts. … But it can help to add the acid really slowly. That way, you slowly change the pH in the milk," she says.
There is no real substitute for butter and cream, Mrs. Corriher maintains.
"Nothing tastes as good as cream," she says. "Fat also carries flavor well. It coats your mouth and allows flavors to last longer."

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