E523 - Aluminium ammonium sulphate

At a glance

• What it is: a crystalline alum salt (ammonium alum) used as a stabiliser and firming aid.
• How it looks: clear to white crystals, usually as a hydrated solid.
• Where you might see it: selected pickled or preserved foods, and other niche uses; labeling may show “E523” or “aluminium ammonium sulphate.”
• Related additives: other aluminium sulphates such as aluminium sulphate (E520) and aluminium potassium sulphate (E522).
• Regulation: permitted with specifications; total aluminium intake from all sources is regulated and monitored.
• Typical role: helps firm or stabilise texture; can provide acidity in certain leavening systems.

Why is Aluminium ammonium sulphate added to food?

Manufacturers use E523 because it helps food hold its shape and texture. As a stabiliser, it can strengthen gels and plant tissues, support foams, and help keep mixtures uniform during processing and storage. In some recipes, alum-type salts provide a mild, slow-acting acidity that pairs with baking soda for controlled leavening.

What foods contain Aluminium ammonium sulphate?

E523 is a niche additive. You’re most likely to find it in certain pickled or preserved vegetables, or in specialty bakery and confectionery systems where a stabilising alum salt is useful. Usage varies by country and product type. If present, it will appear on the ingredient list as “aluminium ammonium sulphate” or “E523.”

What can replace Aluminium ammonium sulphate?

Alternatives depend on the job it is doing in a recipe:

• For firming or crispness in pickles and vegetables: calcium chloride or calcium sulphate.
• For acidity or leavening systems: citric acid with baking soda (sodium bicarbonate).
• For thickening or stabilising: pectins, xanthan gum, agar, or carrageenan.

If the goal is to avoid aluminium altogether, choose non-aluminium options rather than other alum salts such as aluminium sulphate or aluminium potassium sulphate.

How is Aluminium ammonium sulphate made?

Ammonium alum is produced by dissolving aluminium sulphate and ammonium sulphate in water and crystallising the mixed solution to form the hydrated salt, typically the dodecahydrate. Its defined composition for food use is ammonium aluminium sulphate dodecahydrate, written as NH4Al(SO4)2·12H2O.¹ The same identity and formula are also listed in major chemical databases.²

Is Aluminium ammonium sulphate safe to eat?

In the United States, “alum” (including ammonium alum) is listed by the Food and Drug Administration (FDA) as Generally Recognized as Safe (GRAS) when used in accordance with good manufacturing practice.³ In the European Union, E523 is authorised as a food additive with purity specifications set in law.¹

Safety assessments also consider total aluminium from all dietary sources. The European Food Safety Authority (EFSA) set a tolerable weekly intake (TWI) of 1 mg aluminium per kilogram of body weight per week for aluminium compounds in food and drinking water.⁴ This means all sources of aluminium in the diet—including aluminium-containing additives—should be managed so average intake stays below that level.

Does Aluminium ammonium sulphate have any benefits?

• It helps keep pickled vegetables crisp and maintains structure during heat processing.
• It can stabilise foams and gels, supporting consistent texture in certain sweets or bakery fillings.
• In some leavening systems, it provides a controlled, slow-acting acidity that works with baking soda for even rise.

Who should avoid Aluminium ammonium sulphate?

• People aiming to reduce aluminium exposure should read labels and choose non‑aluminium alternatives where possible, especially if their diet already includes other aluminium sources. Guidance in the EU uses the TWI of 1 mg/kg body weight/week to frame overall intake.⁴
• Individuals with reduced kidney function, and very young infants, may clear aluminium from the body less efficiently; a cautious approach to aluminium intake is sensible for these groups.⁵

If you have a medical condition or specific dietary needs, consult a healthcare professional for personalised advice.

Myths & facts

• Myth: “All alums are the same.”
  Fact: There are several alum salts. E523 is ammonium alum; others include aluminium sulphate (E520) and aluminium potassium sulphate (E522). They have similar chemistry but different uses and specifications.
• Myth: “Aluminium additives are unregulated.”
  Fact: Aluminium‑containing additives are regulated, with strict identity and purity criteria, and authorities set health‑based guidance levels for total aluminium intake.¹
• Myth: “If an ingredient contains aluminium, it’s automatically unsafe.”
  Fact: Safety depends on total exposure. Regulators evaluate overall aluminium intake from all foods and set limits intended to protect health.⁴

Aluminium ammonium sulphate in branded foods

Brand use varies by country and product style. To check a product:

• Look for “aluminium ammonium sulphate,” “ammonium alum,” or “E523” on the ingredient list.
• For similar roles without aluminium, look for alternatives such as calcium chloride, citric acid, or stabilising gums like xanthan gum.

References

Footnotes

1. Commission Regulation (EU) No 231/2012: Specifications for food additives (includes E523 ammonium aluminium sulphate). https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0231 ↩ ↩² ↩³

2. Aluminum Ammonium Sulfate Dodecahydrate — PubChem, NIH. https://pubchem.ncbi.nlm.nih.gov/compound/24811 ↩

3. Sec. 182.1125 Alum (ammonium, potassium, and sodium) — U.S. FDA (eCFR). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-182/subpart-B/section-182.1125 ↩

4. Aluminium in food and drinking water: Scientific Opinion — European Food Safety Authority (EFSA). https://www.efsa.europa.eu/en/efsajournal/pub/754 ↩ ↩² ↩³

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