E924A - Potassium bromate

At a glance

• What it is: an inorganic oxidizing salt used as a flour treatment and dough-strengthening aid.
• Where it’s used: primarily in wheat flour doughs for bread, rolls, and similar baked goods made with “bromated flour.”
• How it’s labeled: “potassium bromate,” “bromated flour,” or “E924a.”
• Regulatory snapshot: permitted for specific uses and limits in the United States; listed for cancer risk in California; classified by an international WHO agency (IARC) as possibly carcinogenic to humans.

Why is potassium bromate added to food?

Bakers add potassium bromate to make dough stronger and more tolerant on high-speed lines. As an oxidizing “maturing agent,” it improves dough handling and helps loaves rise evenly. In U.S. regulations, it is listed as a flour-maturing agent for specified uses and conditions of use.¹

What foods contain potassium bromate?

The classic application is “bromated flour,” a standardized flour that includes potassium bromate within a set limit. Products made with this flour can include breads, rolls, buns, and pizza crusts from commercial bakeries. U.S. standards of identity describe bromated flour and cap how much potassium bromate it may contain.²

What can replace potassium bromate?

Bakers often reach for alternatives that provide similar dough-strengthening or maturation effects:

• Ascorbic acid (vitamin C)
• Enzymes such as alpha-amylase
• L-cysteine for dough relaxation in certain formulas
• Oxidizing conditioners like calcium iodate or potassium iodate
• Peroxides used in some regions, such as calcium peroxide
• In some markets, azodicarbonamide has been used as a dough conditioner

The best substitute depends on flour quality, process, and the specific texture a baker wants.

How is potassium bromate made?

Potassium bromate is an inorganic salt with the formula KBrO3. It is a strong oxidizing agent typically produced by oxidizing bromide solutions, and it appears as a white crystalline solid.³

Is potassium bromate safe to eat?

Safety depends on how and where it’s used, and on bake conditions:

• In the United States, potassium bromate is permitted for use in flour and bakery applications when used as specified by regulation.¹ U.S. standards for “bromated flour” set a maximum level for potassium bromate in the flour.²
• An international WHO agency, the International Agency for Research on Cancer (IARC), classifies potassium bromate as “possibly carcinogenic to humans” (Group 2B).⁴
• California lists potassium bromate under Proposition 65 for cancer risk notification.⁵
• During baking, bromate is intended to convert to bromide; however, conditions such as under-baking or very short bake times can influence how much remains.⁴

Does potassium bromate have any benefits?

Technologically, it can make doughs stronger and more tolerant, helping achieve consistent volume and shape in pan breads and rolls. In U.S. regulations, it is recognized as a flour-maturing agent for these functional effects when used under prescribed conditions.¹

Who should avoid potassium bromate?

• People who prefer to minimize exposure to ingredients listed for cancer risk (for example, those following California Proposition 65 warnings) may choose products made without bromate.⁵
• Consumers concerned by IARC’s “possibly carcinogenic” classification may prefer non-bromated alternatives.⁴
• If you’re unsure, look for “unbromated flour” or check the ingredient list for “potassium bromate” or “E924a.”

Myths & facts

• Myth: Potassium bromate and bromide are the same. Fact: Bromate (BrO3−) is a stronger oxidizer than bromide (Br−) and behaves differently in dough and during baking.³
• Myth: All U.S. bread contains bromate. Fact: Its use is permitted but not required; many bakeries use alternatives or label products as “unbromated.”
• Myth: It adds flavor. Fact: Its role is functional (dough strengthening and maturation), not flavoring.¹

Potassium bromate in branded foods

• What to look for on labels: “potassium bromate,” “bromated flour,” or “E924a.”
• Where it appears: primarily in the ingredient list of packaged breads and rolls; in-store bakery breads may provide ingredient info on shelf tags or company websites.
• If unclear: contact the brand or bakery and ask whether they use bromated or unbromated flour, and what dough conditioners they use instead (for example, ascorbic acid or enzymes like alpha-amylase).

References

Footnotes

1. 21 CFR 172.730 — Potassium bromate. U.S. Food and Drug Administration (eCFR). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-172/subpart-G/section-172.730 ↩ ↩² ↩³ ↩⁴

2. 21 CFR 137.155 — Bromated flour. U.S. Food and Drug Administration (eCFR). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-137/subpart-B/section-137.155 ↩ ↩²

3. Potassium bromate — PubChem Compound Summary. National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/Potassium-bromate ↩ ↩²

4. Potassium bromate. IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Vol. 73. World Health Organization, IARC. https://monographs.iarc.who.int/wp-content/uploads/2018/06/mono73-15.pdf ↩ ↩² ↩³

5. Potassium bromate — Proposition 65 Listing. California Office of Environmental Health Hazard Assessment. https://oehha.ca.gov/proposition-65/chemicals/potassium-bromate ↩ ↩²