When it comes to bread, a nicely browned crust does more than just create a flavorful exterior.
Just as with a well-seared roast or steak, much of the flavor in a loaf of bread resides in its deeply browned crust. But many bakers theorize that the flavorful compounds formed during crust development travel from the crust into the crumb, enhancing the flavor of the loaf inside and out.
To test this theory, we baked two baguettes at the same temperature and for the same amount of time, covering one with a disposable aluminum roasting pan to inhibit color development. (Covering the bread leads to steam on its surface, which prevents it from reaching temperatures high enough to brown.) After both loaves had cooled completely, we removed their crusts and compared the flavor of the two crumbs. Sure enough, tasters found the pale-colored baguette mild and a little bland and preferred the more complex flavor of the crusty one.
The bottom line: Flavor compounds in a browned crust are volatile and travel inward toward the crumb. Always bake bread until the crust is well browned; otherwise the overall taste of the loaf will suffer.