Science fair time approaches, and my daughters are looking for project ideas. A few years back, the oldest thought it would be fun to do a kitchen science project; we baked up batch after batch of blueberry muffins, underbeating, overbeating, and all points in between. She shot photos and proved that overbeating muffin batter does indeed lead to those dreaded tunnels.
With that success, baking drew her in again. She felt a strong pull toward chocolate chip cookies (that’s my girl:-)) so we decided to bake a batch with and without leavening. With a food science degree, as well as all manner of food-related resources at hand, you’d think I would know what leavening does in cookies. (I’ve worked for Betty Crocker, for goodness sake.) But I was clueless as to how cookies would bake up without baking soda or baking powder. I didn’t figure the 1/2 teaspoon was responsible for much actual leavening–cookies are puffy, but don’t rise as do muffins and other quick breads. Why is leavening important?
Just for kicks, we also baked batches with butter and shortening (using the same recipe), knowing that the butter-containing cookies would spread and brown more than the ones with shortening. And the flavor would be far better with butter. Yet, the difference between the two batches was slight and not enough to give it Science Fair status.
The batch sans baking soda, on the far right, is clearly paler and more cake-like. Flavor was flat and once cooled, the cookies had a tougher chew. (Not saying we tossed them in the trash; they were still sweet, rich, and packed with chocolate chips.) But compared to the shortening and butter (best flavor by far–no surprise), they weren’t as tasty.
Since it’s all about the science, I hit Shirley Corriher’s Bakewise to learn more about the exact role baking soda plays in cookies. Corriher confirmed my suspicion that “leavening in most cookies is minimal.” The alkali in baking soda promotes browning (seen in the paler unleavened cookies) as it neutralizes browning-inhibiting acids. Corriher’s book also noted that acidic baked goods (in this case, molasses-rich brown sugar contributed the acid) take longer to set, which was why these cookies baked through more slowly than the others.
Flavor was a bit harder to pinpoint, but the cookies without leavening were off somehow. I’d imagine it was the acid-alkaline balance again: The acid in the brown sugar wasn’t balanced by an alkaline leavener, which had to affect flavor. As for structure–less leavening (no matter how minor the role), less air, more dense, tougher chew.
The project brought me back to my days in Food Chemistry. I love that so many disparate ingredients (flour, leavening, salt, etc) combine, interact, and reemerge as a cake, loaf of bread, batch of cookies. It seems magical, but it’s hard science and can be understood on a molecular level. My daughter will bake more cookies for the science fair and delve into the details. But to most folks (myself included), the magic and allure of chocolate chip cookies will always trump science.