It is the sodium salt of alginic acid (E400). Alginic acid and its salts are used in unlimited quantities in many foodstuffs. They are good thickeners and their use is particularly common in puddings, mousses, jams, ice cream, mayonnaise, yoghurt, soups and sauces. Their consumption does not raise any particular concern.
Very many food categories, prohibited in certain confectionery (choking hazard), authorised in certain baby foods only (desserts and sweets).