Baking with Bleached and Unbleached Flour
Bleached flour and unbleached flour can be used interchangeably in recipes. Milled flour will bleach, or turn white, on its own when allowed to stand exposed to air (unbleached flour). Because this takes time, bleaching agents are added to the flour to turn it whiter (bleached flour).
More Tips for Baking with Flour
We have even more advice for using different kinds of flour, including info on substituting one type of flour for another: