YenzoWhat is E521 (aluminium sodium sulphate)?
E521 is aluminium sodium sulphate, INS number 521.
E521Aluminium sodium sulphate
E521 is aluminium sodium sulphate. Circular 24/2019/TT-BYT has no row for INS 521 in Appendix 1, the list of additives permitted in food.
- Code
- E521 · INS 521
- Group
- Firming agent
In Vietnam✕ Not permitted in VietnamNot on Vietnam's list of permitted additives (Circular 24/2019); it may be used only in a product whose declaration is registered with the Vietnam Food Administration
Risk level on the Yenzo Scalehigh?Because it is not permitted in Vietnam; by the scientific evaluations alone: moderate
EFSA (2008) found that intake in some population groups can exceed the tolerable weekly intake (TWI); the EU therefore cut the maximum use levels and removed some of these additives (Regulation (EU) 380/2012). This is what puts it at the middle level of the Yenzo Scale.
How E521 appears on labels
IngredientsIllustrative example
Wheat flour, vegetable oil, salt, sugar, firming agent (521), dried onion and garlic, pepper, natural colour (160a).
firming agent (521)firming agent 521E521INS 521
Aluminium sodium sulphate in food
Questions about aluminium sodium sulphate
Is aluminium sodium sulphate harmful?
In 2018 EFSA concluded that the aluminium sulphates (E520–E523) are of no safety concern in the current authorised uses and use levels. EFSA noted that they are permitted only in a few specific products, so real exposure is most probably near zero.
Is E521 permitted in Vietnam?
It was not found. Appendix 1 of Circular 24/2019/TT-BYT (consolidated text 09/VBHN-BYT), the list of additives permitted in food, has no row with INS 521, and neither does Appendix 2B.
Can children and pregnant women have INS 521?
In 2018 EFSA estimated exposure to aluminium from this group of additives (E520–E523, E541) by age group. In a highly conservative scenario based on the maximum permitted levels, mean exposure in toddlers and children exceeded the TWI of 1 mg aluminium/kg body weight per week. However, because these additives are only authorised in niche products, EFSA considered the estimates highly uncertain and the real exposure most probably near zero, and concluded there is no safety concern at the current authorised uses and use levels. EFSA's conclusions do not single out pregnant women. If you have a particular health condition, ask a doctor.
Other firming agents
E516Calcium sulphatevery lowE518Magnesium sulphatevery lowE520Aluminium sulphatehighE522Aluminium potassium sulphatehighE523Aluminium ammonium sulphatemoderateE526Calcium hydroxidevery low
See all firming agents →Updated 21 October 2026
Sources (4)
- Commission Regulation (EU) No 380/2012 amending Annex II to Regulation (EC) No 1333/2008 as regards the conditions of use and the use levels for aluminium-containing food additives, https://eur-lex.europa.eu/eli/reg/2012/380/oj. EFSA Journal: Safety of aluminium from dietary intake (2008): tolerable weekly intake 1 mg/kg bw.
- Thông tư 24/2019/TT-BYT (văn bản hợp nhất 09/VBHN-BYT), Phụ lục 1
- EFSA Journal (2018). Re-evaluation of aluminium sulphates (E 520-523) and sodium aluminium phosphate (E 541) as food additives
- Codex CAC/GL 36-1989 (Rev. 2008, Amd. 2015), Section 3: INS 521 Aluminium sodium sulfate