Aluminium ammonium sulphate

Aluminium ammonium sulphate — ammonium alum — is a double sulphate salt composed of aluminium, ammonium, and sulphate. Like other aluminium alum forms, it has historically been used as a firming agent for pickled vegetables and as a leavening acid in baking powder formulations. The ammonium ion it releases during processing can also contribute to pH reduction in certain food applications. Its use in modern food processing is less common than it was historically, as aluminium-free alternatives have become widely available and preferred.

JECFA evaluated aluminium ammonium sulphate in 2006 as part of the comprehensive aluminium additive review and issued a "not allocated" ADI, reflecting the absence of sufficient data to establish a safe daily intake and the general precautionary concern about dietary aluminium accumulation. The ammonium component is metabolised via the urea cycle in healthy individuals and presents no specific concern at food additive use levels; it is the aluminium fraction that drives the precautionary regulatory classification.

Aluminium ammonium sulphate is approved in the EU as E523 for specific food applications with controlled maximum levels. Total aluminium intake from the combination of naturally occurring aluminium in foods and aluminium from multiple food additives (E520–E523, E541, E554–E556) has been identified by EFSA as an area where European populations, particularly children and high consumers of processed foods, may be at risk of exceeding the tolerable weekly intake. Consumers who are aluminium-conscious — including those with kidney conditions or those following precautionary dietary approaches — may prefer to avoid products containing multiple aluminium-containing additives.