INS 331 (iii) is trisodium citrate, often just called sodium citrate, and numbered E331(iii) in Europe. INS 331 covers the sodium citrates; sub-index (iii) is the fully neutralised salt, while (i) and (ii) are the monosodium and disodium salts. Codex lists it as an acidity regulator, emulsifier, emulsifying salt, sequestrant and stabilizer.
It is made by neutralising citric acid with a sodium base such as sodium hydroxide or sodium carbonate. The result tastes mildly salty and slightly tart, much softer than citric acid itself.
Snack makers often pair it with citric acid as a buffer. On Jolly Bears the label lists both under acidity regulator: the acid gives the sour taste, while the citrate holds the acidity at a steady level so the gel sets properly and keeps its texture. It is also on the ingredient list of Denma filled cookies, whose fruit fillings are the kind of product where such buffers are common.
