Potassium bromate

Potassium bromate is a flour treatment agent that was used for decades to strengthen dough structure and improve bread volume and texture. When added to flour, it acts as an oxidising agent that strengthens gluten networks to produce a higher-risen, finer-textured loaf. At the correct baking temperature it is theoretically converted to the harmless bromide ion, but studies showed that residual bromate can remain in finished bread when baking conditions are suboptimal.

No acceptable daily intake has ever been established by JECFA or EFSA for potassium bromate. It has been classified as a possible human carcinogen (IARC Group 2B) based on animal studies showing kidney tumours, thyroid tumours, and peritoneal mesotheliomas at high doses. Residual bromate has been detected in commercially produced bread in multiple countries, making the theoretical safety margin unreliable in practice.

Potassium bromate is banned as a food additive in the European Union, the United Kingdom, Canada, Brazil, China, Nigeria, and many other countries. Japan banned its use in 2000. It remains technically permitted but strongly discouraged in the United States, where the FDA has urged voluntary elimination; California requires a Proposition 65 carcinogen warning on bread made with it. Consumers in markets where it remains legal should check bread labels and choose products that do not list potassium bromate.