Potassium bromate is a chemical additive used in flour to improve the action of the gluten. Gluten is a protein in wheat flour that gives bread dough its elasticity during kneading and that allows dough to rise by trapping gases produced by yeast. By strengthening the gluten, potassium bromate results in bread that rises higher and is more likely to hold its shape. The potassium bromate that’s added to flour is supposed to bake out of the bread dough as it cooks. However, if too much is added, or if it’s not cooked properly, it is possible for some of the chemical to remain in the finished product.
The International Agency for Research on Cancer, or IARC, labeled potassium bromate as a category 2B carcinogen.
Potassium bromate has been banned from use in food products in Europe and Canada. It has not been banned in the United States, but the U.S. Food and Drug Administration asked bakers to voluntarily choose other additives, and federal regulations limit the amount that can be added to flour. Following guidelines established under its Safe Drinking Water and Toxic Enforcement Act, the State of California includes potassium bromate on its list of chemicals known to cause cancer and requires products containing bromated flour to carry a warning label
To avoid the substance, do not purchase foods that have “bromated flour” or “potassium bromate” in their list of ingredients.