Bleached Flour - Wheat flour that has been exposed to chlorine gas or benzoyl peroxide to mature the flour and condition the gluten, improving the baking quality. The bleaching agent evaporates and does not leave residues or destroy the nutrients. It also reduces the risk of spoilage or contamination. Enriched refers to the presence of vitamins or minerals contained in the flour, commonly; niacin, ferrous sulfate, thiamin mononitrate, riboflavin and folic acid. Technically speaking, the carotenoid (yellow) pigments in the flour are oxidized to produce white flour. Flour treated with these bleaching agents must be labeled as bleached. A main difference between unbleached and bleached flour is the color; one is off-white and the other is pure white. .