Instructions: Have you ever had a cake that rose beautifully, but five minutes before it was to come out of the oven, it fell in the center? You might think that when cakes or muffins fall or are heavy, they need more baking powder, but often the opposite is true: the problem may be too much leavener.

I get phone calls about overleavening problems every week, and a colleague with a call-in cooking show says this is one of the problems she hears about most frequently. Someday Ill go through a stack of cookbooks to see just how many recipes are overleavened.

Baking powder and soda must be in balance.

By leavening, of course, I mean baking soda and baking powder, not yeast.

Baking soda is sodium bicarbonate, which when heated breaks down to form some carbon dioxide gas and sodium carbonate-a salt with a soapy taste. However, the major gas production occurs when baking soda combines with an acid. In this case, a milder tasting salt is left behind.

Baking powder contains baking soda and the exact amount of acid to balance the soda, along with some cornstarch to keep the two active ingredients separate and dry.

When you have too much of either of these chemical leaveners, the gas bubbles in the batter get big, bump into each other, become huge, float to the top, and then pop-there goes your leavening.

So what is the correct amount of leavener? In most recipes, 1 to 1-1/4 teaspoons baking powder per cup of flour provides ideal leavening (see the chart below). Some baked goods with a lot of heavy ingredients, like a carrot cake, may need a little more leavening, but not much.

Chemical leavener needed per cup of flour These ratios are good to remember so you can evaluate recipes before you try them and so you can successfully tinker with or create your own recipes.

For nonacidic recipes:
1 cup flour
1 to 1-1/4 tsp. baking
powder
For very acidic recipes:
1 cup flour
1/2 tsp. baking powder
and
1/8 tsp. baking soda

(Note: Baked goods with a lot of heavy ingredients, like carrot cake, may need a tiny bit more leavening.)

In most recipes, baking powder is preferred because of its reliability (it contains exactly the right amount of acids to completely neutralize all the soda, leaving no aftertaste) and because of its double action (one acid dissolves when water is added, producing bubbles, and another acid does not dissolve and produce leavening until a higher temperature is reached in the oven). Sometimes youll see a double-acting baking powder with only one acid in the list of ingredients. This product may use encapsulation, like time-release cold pills, to produce leavening at different times.

Baking soda is normally used in recipes that contain acidic ingredients such as sour cream, buttermilk, brown sugar, or chocolate. You need to remember, though, that the soda isnt just neutralizing acids: its also making bubbles, and it can easily overleaven.

Muscle-man soda is often the culprit. Frequently, overleavening is caused by an excessive amount of soda. Many cooks and recipe writers dont realize the strength of baking soda. A whole teaspoon of baking powder contains only 1/4 teaspoon baking soda as its major active ingredient.

Solving the mystery of the concave cake

A test kitchen asked me about a cake recipe that called for adding boiling water to the soda, letting it stand, and then combining it with other ingredients. Sometimes the cake worked, and sometimes it fell. What we figured out was that the recipe had too much soda, but if the cook allowed the soda to stand long enough with the boiling water, enough of the gases came off to prevent the cake from falling. If it didnt stand long enough, the cake was badly overleavened and fell. Recipes like this are tricky, to say the least.

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