Silicon Dioxide
What it does
Anti-caking agent.
How it's made
Purified silica.
Silicon dioxide, also known as silica, is used as an anti-caking agent to keep powdered and granular foods (such as spices, powdered soups, salt and coffee whitener) dry and free-flowing. It is chemically the same substance as quartz and sand, but the food-grade material is an extremely fine, fluffy powder rather than gritty grains.
The food-grade product is generally a synthetic "amorphous" silica rather than mined sand. It is made either by a flame process, in which a silicon compound is burned to produce very fine fumed silica, or by a wet route in which a solution of sodium silicate ("water glass") is treated with acid to precipitate silica particles. Both give a very pure, high-surface-area powder.
The precipitated or fumed silica is washed, dried and milled to a light powder whose enormous surface area lets it soak up small amounts of moisture and coat other particles, keeping them separate. The food grade is amorphous, meaning it lacks the crystalline structure of quartz that makes mineral dust a workplace hazard.
Possible reactions
Generally inert and safe.