For example, the equivalent of baking powder is baking soda and an acidic ingredient.
Instead of one teaspoon of baking powder, you can use 1/2 teaspoon cream of tartar plus 1/4 teaspoon baking soda, according to "Betty Crocker's New Cookbook."
Consumers have the most trouble with substituting cooking oils and fats, says Jeanie Kozar, a Betty Crocker home economist.
Margarine and butter both have a fat content of 80 percent, and they can be interchanged in recipes. It's best to use them in stick instead of whipped form.
Vegetable oil spreads, which can have a fat content as low as 30 percent, should not be substituted for margarine or butter, Kozar says.
Some cookbooks contain a list of ingredients that can be substituted in an emergency.
While the changes will not produce identical results, they will be very close, Kozar says.
When baking with chocolate, the only substitution that produces an exact result is cocoa exchanged for unsweetened baking chocolate, Reitz says. She notes that 3 level tablespoons of cocoa plus 1 tablespoon of liquid or solid shortening equals 1 ounce of unsweetened baking chocolate.
Bittersweet and semisweet chocolate are interchangeable, Reitz says.
Today's health-conscious cooks also are making substitutions to reduce the fat content in recipes.
When you take out the fat, you change a recipe's character, texture and flavor.
If you're thinking about using a substitute such as applesauce for some of the fat, don't replace more than half, Kozar recommends. If you do, the change will be so dramatic that you probably won't be happy with the result, she says.
You need to increase the flavor when you reduce the fat, and one way is to add more vanilla.
When Kozar alters a recipe, she jots down what she changed in the margins of her cookbook. She also notes the date and if she liked the result.
Toth says some people think that a recipe is carved in stone, and they're afraid to experiment.
"Just because it's written down doesn't mean it has to be that way," he says.
Toth, who teaches a low-fat cooking class through Hagerstown Junior College, recently showed his students how to cut the fat in a Chicken Cordon Bleu recipe by 15 grams. He replaced the ham with 91 percent fat-free ham, Swiss cheese with mozzarella and whole eggs with egg whites.
"It tasted just the same," he says.
Reitz says it's best to use a recipe that has been developed to be low-fat than to spend a lot of time trying to alter it, because you may be disappointed with the finished product.
"Let us do the work; that's what we get paid for," she says.