How are bleached and unbleached flour different?
What’s the difference between bleached and unbleached flour?
Over the course of several months, the color of unbleached flour will turn from beige to white. To expedite this process, many companies "bleach" flour with chemicals, most often chlorine gas or benzoyl peroxide. These chemicals lower the protein content of the flour and make it more likely to yield tender baked goods. Some critics claim that bleaching also imparts an off flavor.
To judge any flavor or textural differences for ourselves, we prepared batches of biscuits with unbleached and bleached flour and held a blind tasting. Though some astute tasters detected a faint "raw," "artificial" flavor in the batch made with bleached flour, most people agreed that both batches of biscuits were acceptable. (Note that even our pickiest tasters couldn't detect any differences between bleached and unbleached flour in yellow cake or chocolate chip cookies, recipes where other ingredients overwhelm the flavor of the flour.) Based on these tests, we have a slight preference for unbleached flour (which is what we use in the test kitchen), but bleached flour is fine, too