Calcium aluminium silicate

Calcium aluminium silicate is a synthetic aluminosilicate compound approved for use as an anti-caking agent in powdered and granulated food products. It prevents particle adhesion and moisture-induced caking, preserving the free-flowing texture of table salt, dried soup powders, powdered creamers, and similar products during storage. As with related compounds in the E550–E559 range, it is used in very small quantities and functions by adsorbing surface moisture before it can promote inter-particle bonding.

JECFA last evaluated calcium aluminium silicate in 2006 and concluded that a numerical ADI could not be allocated. This "not allocated" outcome resulted from a combination of insufficient quantitative data and wider concerns about total dietary aluminium intake. The calcium content does not confer a safety advantage over the pure silicate form; the aluminium component remains the focus of the precautionary approach. Aluminium bound within a mineral silicate lattice is less bioavailable than ionic aluminium, but this does not eliminate concern at high cumulative dietary intakes.

Calcium aluminium silicate is approved in the EU and listed under E556 for use in specific permitted food categories with defined maximum levels. The European Food Safety Authority has issued guidance recommending that total aluminium intake from additives, packaging, and naturally occurring sources be monitored, particularly for high consumers. Informed shoppers who wish to minimise aluminium in their diets may seek out products using non-aluminium anti-caking agents. Most healthy adults process dietary aluminium without issue, but children and individuals with kidney conditions may benefit from more careful monitoring of exposure from food sources.