Agar
What it does
Gelling agent (vegan gelatine substitute).
How it's made
Extracted from red seaweed.
Agar (agar-agar) is a natural gelling agent extracted from red seaweeds, used to set jellies, desserts and confectionery and as a vegetarian alternative to gelatine. It forms a firm gel that, unusually, stays solid at room temperature and even in warm conditions, and it is also the classic gel used to grow microbes in laboratories.
It is obtained from red seaweeds (such as Gelidium and Gracilaria), which are washed and then boiled in water to dissolve out the agar. The hot extract is filtered to remove seaweed residue, and the agar is recovered by cooling it into a gel, which is then frozen and thawed (or pressed) to squeeze out water and concentrate it, before drying.
The dried agar is milled into a powder or flakes. It gels very strongly, so only a small amount is needed, and its high melting point makes it useful for jellies that must hold up in warmth; being seaweed-derived, it is fully vegetarian and vegan, which is a major reason for its popularity.
Possible reactions
Generally safe; laxative in large amounts.