E521: Aluminium Sodium Sulphate
Main role: firming specified foods
Also listed as: sodium alum, soda alum, aluminum sodium sulfate
What is E521 (Aluminium Sodium Sulphate)?
E521 is a double sulphate salt containing aluminium and sodium. It belongs to the specified alum group with limited food applications and has a different identity from sodium sulphate E514.
What does it do in food?
Its main role is firming specified foods. Mineral ingredients can adjust acidity, firm a food, or keep powders flowing. A technical mineral ingredient does not establish a nutritional dose; use the nutrition declaration to assess amounts per serving.
Food and formulation examples
- Specified fruit preparations
- Narrowly authorized firming uses
These examples describe formulation roles, not a list of unrestricted legal uses. Availability and permitted applications differ by country and food category.
Label names and ingredient questions
Look for E521, E 521, or the ingredient name. Related names and label terms include sodium alum, soda alum, aluminum sodium sulfate. A family code can cover more than one specified form; check the full declaration when the distinction matters.
Sodium alum and ordinary sodium sulphate are distinct ingredients. Use the complete name and permitted category rather than assuming the word sodium describes the whole compound.
Is E521 safe?
EFSA’s 2018 review assessed aluminium sulphates and acidic sodium aluminium phosphate specifically. This is a different assessment from the 2019 review of other phosphate additives. EFSA aluminium-containing additives review (2018).
A label identifies the ingredient but usually not its concentration. Calculating daily intake requires the amount in the food and the quantities eaten.
Authorization and conditions of use
The Great Britain food additive register lists E521 as Aluminium sodium sulphate. This is an entry subject to its stated conditions, not unrestricted permission for every food. The record links to the applicable authorization terms. For an EU product, use the European Commission food additive database to check the relevant food category and limits. Other countries may use different names or rules.