Q: The enclosed recipe for spice bread is delicious, but the center always caves in. Do you know why?
A: There are three problems with this recipe: One, the instructions say to "beat in eggs." Two, the amount of brown sugar is excessive. And three, the recipe calls for about a third more baking soda than necessary. All three faults will contribute to a collapse. In the following revision, the instructions have been changed to "blend in eggs," the brown sugar has been reduced from 2 cups to 1 1/2 cups, and the baking soda has been cut by 30 percent. SPICE BREAD (Makes 2 loaves)
2 2/3 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon salt
1 1/2 teaspoons cinnamon
1/2 teaspoon each: nutmeg, cloves, allspice
3/4 cup softened butter
1 1/2 cups dark brown sugar
3 eggs, room temperature
1 1/2 cups buttermilk, room temperature
1 cup chopped pecans, walnuts or raisins
Sift flour and baking soda together. Add salt and spices and set aside. Cream butter and sugar at low speed for 5 minutes. Add 1 egg and blend. Then add another egg, a spoonful of the flour mixture and blend. Add the third egg, blend in, pour in the sifted flour mixture all at once and then all the buttermilk. Turn the mixer to medium speed and scrape the bowl's edges. When the batter is smooth, add the nuts or raisins and turn off the mixer.
Pour batter into 2 greased 8-by-4-inch loaf pans. Bake at 350 degrees for 45 to 55 minutes or until a toothpick inserted into the center emerges clean.
From this recipe one can learn three lessons:
1. Don't beat eggs into a cake batter. Blend them in. Beating creates large air cells. These expand during baking and either rise to the surface of the batter, where they pop, or they stretch the batter's proteins beyond their limits of extensibility and the batter's cell structure collapses. Blending creates more, finer air cells that are more likely to stay in place and less likely to coalesce.
2. While adequate sugar produces a moist cake, an excess of sugar leads to collapse. Sugar delays the swelling (gelatinization) of starch granules and the setting of the batter. Should its setting be delayed too long, the leavened batter succumbs to gravity.
3. A little baking soda is desirable; a lot is not. Baking soda neutralizes the lactic acid of buttermilk, helps leaven the cake and deepen its color. Too much baking soda, however, causes excess aeration, overinflates the batter and leads to collapse. An excess of soda also cause scorching, because the browning reduction is enhanced by a mildly alkaline batter.
Q: What is the secret to baking cakes that are flat on top rather than domed?
A: There are two causes of doming: a thick batter and a large cake. Both causes are the results of temperature difference between the outer edges of a cake and its center. A cake's outer edges reach a higher temperature than its center.
A thick cake batter results when you add too much flour to it. Flour's wheat proteins bind water and prevent its molecules from moving throughout to distribute heat. Consequently, the cake batter in the center of the pan sets more slowly than the batter at the edges. Hence the center continues to swell up while the edges of the cake have long since set.
In a large, deep cake, even a thin batter can develop a domed top -- for the same reason as just described.