Which ingredient is primarily responsible for the structure in baked goods?

Flour is the key ingredient responsible for providing structure in baked goods. It contains proteins such as glutenin and gliadin, which, when mixed with water and kneaded, form gluten. This gluten network is crucial because it gives baked goods their shape and texture. The structure created by gluten allows the product to rise and maintain its form during and after baking.

While other ingredients like sugar, baking soda, and butter play significant roles in flavor, tenderness, and leavening, they do not primarily contribute to the structural integrity of the final product. Sugar, for instance, can enhance browning and sweetness, while baking soda serves as a leavening agent that helps dough rise by producing carbon dioxide. Butter contributes to flavor and moisture, but it also creates a tender crumb rather than providing structure. Thus, flour is the fundamental ingredient that forms the backbone of baked goods.