A Comprehensive Explanation of How Flour Bleaching Agents Work and Their Safety

Flour bleaching agents are a class of food additives added to wheat flour. Their main function is to oxidize and break down pigment components such as carotenoids in the flour, turning flour that was originally slightly pale yellow into a pure white color. Common varieties include benzoyl peroxide, calcium peroxide, chlorine dioxide and others, among which benzoyl peroxide is the most typical. These substances can also speed up the post-maturation process of freshly milled flour, shortening the time needed for the flour to change color during storage.

In terms of how they work, bleaching agents slowly release active oxygen within the flour, oxidizing and fading pigments such as lutein while also providing a certain gluten-strengthening effect. However, the oxidation process may also destroy some nutrients in the flour, such as certain vitamins, and once added in excess it can create residue risks that affect food safety.

It is precisely because of these controversies that attitudes toward flour bleaching agents differ from region to region. Some places have already explicitly banned them, while others allow their use within limited doses. In fact, when freshly milled flour is stored naturally for a period of time, the pigments will likewise oxidize and fade on their own, and the color gradually turns white. This is also what is traditionally meant by post-maturation treatment.

For consumers, flour is not better the whiter it is. Moderately processed flour usually has a natural milky white or slightly yellowish color, while whole wheat flour, because it retains the bran, is normally yellowish-brown. If whiteness is pursued through bleaching, nutrients may instead be lost. When buying, rather than focusing on whiteness, it is better to check whether the ingredient list is simple and whether the product labeling is complete, as this makes it easier to buy flour of reliable quality.