AP flour vs. cake flour in this recipe to avoid sinking in the middle
#14512: Marilyn, I sent Cindy Mushet from "Art & Soul of Baking" this thread...here's her response:
Posted by: Traca at 2:35 pm on Apr 22, 2009
Hi Traca, My first thought when something sinks in the middle is too much leavening (yeah, weird, the bubbles in the batter expand too much, bump into each other and pop). The measuring spoons should be level at the top. Just looking at the formula, it looks like there's more leavener in here than needs to be, but the rule of 1 teaspoon baking powder per 1 cup flour can be bent for certain textural results.
If that's not the issue, then my next guess would be the flour. You need enough gluten to hold the cake up - think of gluten as the frame of a house. Protein content in the flour is directly responsible for the amount of gluten that can develop with mixing. Cake flour has the least amount of protein and bread flour has the most. I think the addition of ricotta is causing the problem - brands of ricotta vary in their moisture content, and the batter may be too wet in some cases. You may need a little extra flour to absorb that liquid and provide structure. Maybe increase the cake flour to 1-3/4 cups and see if that helps. Or, use a flour with more protein, such as unbleached all purpose flour, which is able to absorb more liquid than cake flour, and provide more structure as well. I'd start with 1-1/4 cups unbleached all purpose flour to substitute for the 1-1/2 cups cake flour.
By the way, with pound cakes, the butter needs to be about 65 F. to 68 F. for best results with creaming. That's cool to the touch and flexible - you could bend it into a sculpture and it would hold its shape. If the butter is warmer than that, your results won't be as good, since warm butter can't hold all the air bubbles that form during the creaming process, which results in a heavy, under-risen cake. For the best rise in these dense cakes, they need to be filled with air bubbles. The baking powder helps the bubbles enlarge in the heat of the oven, which in turn makes the cake rise. Keep the butter on the cool side, then beat with the sugar for a full 5 to 6 minutes, or until it looks nearly white. And make sure any other ingredients you add are at cool room temperature (not warm), so they don't "seize" the butter - adding something cold to the mixture makes it contract quickly, which also collapse air bubbles.
Hope something here helps! I'm going to try the cake - it sounds delicious!
Take care,Cindy