Potassium bromate (KBrO₃), is a

bromate The bromate anion, BrO, is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate, (), and potassium bromate, (). Bromates are formed many different ways in municipal drin ...

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

and takes the form of white crystals or powder. It is a strong oxidizing agent. It is a toxic and carcinogenic compound.

Preparation

Potassium bromate is produced when

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

is passed through a hot solution of

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

. This first forms unstable potassium hypobromite, which quickly disproportionates into bromide and bromate: : 3BrO⁻(aq) → 2Br⁻(aq) + (aq) Electrolysis of potassium bromide solutions will also give bromate. Both processes are analogous to those used in the production of chlorates. Potassium bromate is readily separated from the potassium bromide present in both methods owing to its much lower solubility; when a solution containing potassium bromate and bromide is cooled to 0°C, nearly all bromate will precipitate, while nearly all of the bromide will stay in solution.

Uses in baking

Potassium bromate is typically used in the United States as a flour improver ( E number E924). It acts to strengthen the

dough Dough is a thick, malleable, sometimes elastic paste made from grains or from leguminous or chestnut crops. Dough is typically made by mixing flour with a small amount of water or other liquid and sometimes includes yeast or other leavenin ...

and to allow higher rising. It is an

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

, and under the right conditions will be completely reacted to a form with a lower

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

in baking the bread. However, if too much is added, or if the bread is not baked long enough or not at a high enough temperature, then a residual amount will remain, which may be harmful if consumed. Potassium bromate might also be used in the production of malt barley, for which application the

U.S. Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

(FDA) has prescribed certain safety conditions, including labeling standards for the finished malt barley product. It is a very powerful oxidizer (E° = 1.5 volts, comparable to

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

Regulation

Potassium bromate is classified as a category 2B

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...

by the

International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...

(IARC). Potassium bromate has been banned from use in food products in the European Union, Argentina, Brazil, Canada, Nigeria, South Korea, Peru, and some other countries. It was banned in Sri Lanka in 2001, China in 2005, and India in 2016. In the United States, it has not been banned. The FDA sanctioned the use of bromate before the

Delaney clause The Food Additives Amendment of 1958 is a 1958 amendment to the United States' Food, Drugs, and Cosmetic Act of 1938. It was a response to concerns about the safety of new food additives. The amendment established an exemption from the "food addit ...

of the

Food, Drug, and Cosmetic Act The United States Federal Food, Drug, and Cosmetic Act (abbreviated as FFDCA, FDCA, or FD&C) is a set of laws passed by the United States Congress in 1938 giving authority to the U.S. Food and Drug Administration (FDA) to oversee the safety of f ...

—which bans potentially carcinogenic substances—went into effect in 1958. However, since 1991 the FDA has urged bakers to voluntarily stop using it. In

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

, a warning label is required when bromated flour is used. Japanese baked goods manufacturers stopped using potassium bromate voluntarily in 1980; however, Yamazaki Baking resumed its use in 2005, claiming they had new production methods to reduce the amount of the chemical which remained in the final product.AsiaPulse News: Japan's Yamazaki Baking to use potassium bromate in bread
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References

{{E number infobox 920-929 Bromates Potassium compounds IARC Group 2B carcinogens Oxidizing agents Food additives