E522 - Aluminium potassium sulphate

At a glance

• Other names: potassium alum, potash alum, potassium aluminium sulfate
• What it does: firms fruits and vegetables; provides acidity for certain leavening systems
• Where it’s found: some pickled vegetables and a few baking powders; overall use is limited
• Safety: regulated in the EU and U.S.; total dietary aluminium exposure is controlled by strict limits

Why is Aluminium potassium sulphate added to food?

Food makers use E522 mainly to keep produce crisp and to adjust acidity. As a “leavening acid,” it can react with baking soda to release carbon dioxide, helping some doughs rise in a controlled way. In practice, other aluminium salts such as sodium aluminium sulfate or sodium aluminium phosphate are more common in baking, so potassium alum is a relatively niche choice today.¹

What foods contain Aluminium potassium sulphate?

You may find E522 in:

• Some pickled cucumbers and other firmed vegetables
• A few brands of double-acting baking powder or dry mixes (as one of the acid components)
• Occasional fruit and vegetable processing steps where extra firmness is desired

Label lines can list it as “alum,” “potassium alum,” “aluminium potassium sulphate,” or “E522.”

What can replace Aluminium potassium sulphate?

Depending on the job, common stand-ins include:

• For crispness in pickles and vegetables: calcium chloride or calcium lactate
• For acidity control and tart flavor: citric acid
• For leavening systems in baked goods: monocalcium phosphate, cream of tartar (potassium bitartrate), diphosphates, or, when aluminium salts are desired, sodium aluminium phosphate
• Pairing acid with base: these acids typically react with baking soda (sodium bicarbonate) to produce lift

How is Aluminium potassium sulphate made?

Potassium alum is produced by combining aluminium sulfate with potassium sulfate in water and then crystallizing the double salt as the familiar dodecahydrate KAl(SO4)2·12H2O.² Its identity and purity specifications for food use are set in EU law alongside other listed additives.³

Is Aluminium potassium sulphate safe to eat?

In the United States, alum (aluminium potassium sulfate) appears on FDA’s Food Additive Status List as permitted for use in food, subject to good manufacturing practice.¹ In the European Union, it has official identity and purity specifications, and overall aluminium exposure from all additives is controlled through strict limits.³

Safety assessments focus on total aluminium intake rather than one single aluminium additive. The European Food Safety Authority (EFSA) set a tolerable weekly intake (TWI) for aluminium of 1 mg per kg of body weight per week, covering exposure from food and food additives combined.⁴ Typical consumer intakes are well below this when additives are used as directed.

Does Aluminium potassium sulphate have any benefits?

• Texture: helps fruits and vegetables stay firm after processing
• Processing aid: provides a steady acid source in some leavening systems
• Shelf quality: by supporting texture, it can help maintain an appealing bite in certain preserved foods

It does not add nutritional value.

Who should avoid Aluminium potassium sulphate?

• People with significantly reduced kidney function may need to limit aluminium exposure, because the kidneys clear aluminium from the body less efficiently.⁵
• Infants and very young children are more sensitive to overall aluminium intake on a body-weight basis; caregivers may prefer non‑aluminium alternatives when practical.⁴
• Confusion alert: “sulfate” (as in potassium alum) is chemically different from “sulfite” preservatives. Sulfite sensitivity does not automatically apply to sulfate salts.

If you have a medical condition or a physician’s advice to limit aluminium, choose products that use non‑aluminium firming agents or leavening acids.

Myths & facts

• Myth: “Alum in food is banned.” Fact: Alum is permitted for food use under specific regulations and good manufacturing practice in the U.S. and has EU specifications; authorities control overall aluminium exposure.¹³
• Myth: “All aluminium additives act the same.” Fact: Aluminium salts have different properties and uses. For example, aluminium sulphate, aluminium sodium sulphate, aluminium ammonium sulphate, and sodium aluminium phosphate are not interchangeable in every recipe.
• Myth: “Sulfate equals sulfite.” Fact: Sulfates (like alum) and sulfites (like E220–E228) are different chemical groups; sulfite sensitivity does not mean a person will react to sulfate salts.

Aluminium potassium sulphate in branded foods

On ingredient lists, look for “alum,” “potassium alum,” “aluminium potassium sulfate/sulphate,” or “E522.” You’re most likely to see it on jars of pickled vegetables, some canned produce, and occasionally in baking powders or dry baking mixes that use an alum-based leavening acid. Many brands now favor calcium- or phosphate-based alternatives, so alum may appear less often than in older recipes.

References

Footnotes

1. Food Additive Status List — U.S. FDA. https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩ ↩² ↩³

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

3. Commission Regulation (EU) No 231/2012 — Specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0231 ↩ ↩² ↩³

4. Safety of aluminium from dietary intake — EFSA Journal (2008). https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2008.754 ↩ ↩²

5. Toxicological Profile for Aluminum — ATSDR/CDC. https://www.atsdr.cdc.gov/toxprofiles/tp22.pdf ↩