E922 - Potassium persulfate

At a glance

• What it is: a white, crystalline oxidizer with the formula K2S2O8.
• Typical role: historically a flour treatment and bleaching agent; now uncommon in foods.
• Labels may show: “E922,” “potassium persulfate,” or “potassium peroxydisulfate.”
• Safety note: it can irritate skin, eyes, and airways and may trigger allergic asthma in sensitized people.
• Regulation: only allowed where specifically authorized by law; check your country’s rules.

Why is Potassium persulfate added to food?

When used in food processing, potassium persulfate acts as a powerful oxidizing agent. In flour, oxidizers can bleach pigments and modify dough properties, which can improve whiteness and handling during baking.¹

What foods contain Potassium persulfate?

In the European Union, only additives on the Union list in Regulation (EC) No 1333/2008 (Annex II) may be used, and potassium persulfate (E922) is not included there, so it is not authorized for use in EU foods.²³ In the United States, FDA standards for flour and bleached flour list which bleaching and maturing agents are permitted; potassium persulfate is not among the listed options, so it is not typically found in U.S. flours or baked goods.⁴

If present where allowed, you would most likely see it in flour or premixes for baked goods, declared as “potassium persulfate” or “E922.”

What can replace Potassium persulfate?

Bakers and millers commonly choose other dough improvers or bleaching agents that are authorized in their markets, such as:

• ascorbic acid (dough strengthening)
• L-cysteine (dough softening)
• Enzymes like alpha-amylase (dough handling and volume)
• In some jurisdictions, other oxidizers or maturing agents may be used instead of persulfates; always check local regulations. Related chemicals such as ammonium persulfate have also been used historically, but authorization varies by country.

How is Potassium persulfate made?

Commercially, potassium persulfate is typically produced by electrolytic oxidation of potassium bisulfate or sulfate in acidic solution, followed by crystallization and drying to yield K2S2O8.⁵ The resulting salt is a stable source of the peroxydisulfate ion, which provides strong oxidizing power.⁵

Is Potassium persulfate safe to eat?

Potassium persulfate is a strong oxidizer and can irritate eyes, skin, and the respiratory tract on contact or inhalation, and it may cause allergic asthma in sensitized individuals.¹ Where it is allowed for food use, any application would be at very low levels and subject to regulatory controls; in the EU, only additives on the Union list may be used, and E922 is not listed.²³

Does Potassium persulfate have any benefits?

For consumers, potassium persulfate does not add nutrition or flavor. Its benefits are purely technological—bleaching flour and affecting dough behavior—benefits that can be achieved today with other permitted agents and enzymes.

Who should avoid Potassium persulfate?

People with a history of respiratory allergies or prior sensitization to persulfates (for example, from workplace or cosmetic exposure) may wish to avoid additional exposure to this chemical.⁵ Anyone with known reactions to persulfates should consult a healthcare professional and check product labels where its use is permitted.

Myths & facts

• Myth: E-numbers are always harmful. Fact: E-numbers are simply identifiers for regulated additives; safety depends on the specific substance and the rules in your country.
• Myth: Persulfates are the same as sulfites. Fact: Persulfates are powerful oxidizers; sulfites are preservatives and antioxidants. They are different chemicals with different properties and regulations.
• Myth: If it’s not on an approved list, it must be banned everywhere. Fact: Authorization varies by jurisdiction; always check the rules where you live.

Potassium persulfate in branded foods

Because it is not on the EU Union list and is not listed among permitted agents in U.S. flour standards, potassium persulfate is rarely, if ever, seen on ingredient lists in those markets.³⁴ If you do encounter it where permitted, it should appear as “potassium persulfate,” “potassium peroxydisulfate,” or “E922.”

References

Footnotes

1. Potassium peroxydisulfate (ICSC 0946) — NIOSH/CDC. https://www.cdc.gov/niosh/ipcsneng/neng0946.html ↩ ↩²

2. Regulation (EC) No 1333/2008 on food additives — European Union. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008R1333 ↩ ↩²

3. Commission Regulation (EU) No 1129/2011 establishing the Union list of food additives — European Union. https://eur-lex.europa.eu/eli/reg/2011/1129/oj ↩ ↩² ↩³

4. 21 CFR 137.105 — Flour (U.S. FDA eCFR). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-137/subpart-B/section-137.105 ↩ ↩²

5. Potassium peroxydisulfate — PubChem (NIH). https://pubchem.ncbi.nlm.nih.gov/compound/Potassium-peroxydisulfate ↩ ↩² ↩³