"WHAT IS BLEACHED FLOUR?
Bleach flour is refined white flour that has been artificially aged using a bleaching agent, a maturing agent, or both.
WHY WOULD FLOUR NEED TO BE BLEACHED?
Because people are vain. In our minds, flour should be white.
Freshly milled “white flour” (made using only the endosperm, remember?) isn’t really white. It’s on the yellowish side, the depth of color depending on how much germ and bran still remained after the milling and sifting. But people didn’t want to use yellow flour 100 years ago and they still don’t today. Yellow flour is not attractive to buyers.
Chemicals used in bleaching flour:
"Potassium Bromate – This is what’s added to bromated flour. It doesn’t change the color of flour, but it artificially ages it through oxidation. It’s very powerful, sometimes going to the extent of damaging flour cells during the oxidation process. Potassium bromate will be listed as an ingredient or additive, or otherwise noted on flours that contain it.
Benzoyl Peroxide – This bleaches and has no effect on glutenins nor the creation of gluten. It’s the most common bleaching agent in the U.S. (often added with other stabilizing chemicals) and it’s the powder version of the same ingredient many of you may have in your bathroom cabinets. It’s often used as an inexpensive way to lighten hair and it’s the key active ingredient in many whitening toothpastes.
Azodicorbonamide – This is used as both an aging and bleaching agent in flour, although it’s more commonly used to make foam plastics. It turns into biurea in raw dough and baked bread and biurea is quickly excreted via urine. (source)
Chlorine Gas – Used as both a bleaching and maturing agent, although it weakens the development of gluten instead of strengthening it. It’s nearly always used in cake flours since it allows the fat in baked goods like cakes, cookies and biscuits to distribute more evenly, thus creating a better rise and reducing the chance of collapse.
Nitrogen Dioxide – One of the first agents used to bleach flour, but also acts as an aging agent.
Ascorbic Acid – This is primarily used as aging agent, but can also be used as a dough enhancer. Like potassium bromate, it should be listed as an ingredient or additive, but you won’t know for sure what purpose it was used for.
Those are just the chemicals associated with bleaching flour that I could find information on. There’s a few more out there where information in scarce, other than they could potentially be in your flour too:
nitrogen tetroxide (used in bleaching and aging)
nitrosyl chloride (used in bleaching and aging)
chlorine dioxide (bleaching only)
calcium iodate (aging only)
calcium peroxide (aging only)"
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