INS 341 (i) is calcium dihydrogen phosphate, better known as monocalcium phosphate (MCP), and numbered E341(i) in Europe. INS 341 covers the calcium phosphates; sub-index (i) is the most acidic of the three, the others being (ii) dicalcium phosphate and (iii) tricalcium phosphate.
It is made by reacting phosphoric acid with a calcium source such as lime. Codex gives it a long list of functions, among them acidity regulator, anticaking agent, firming agent, flour treatment agent and raising agent.
Its classic role is as the acid in baking powder. As soon as a batter is mixed, MCP reacts with sodium bicarbonate (INS 500 (ii)) and releases carbon dioxide, so bubbles start forming early. On Violet Orange Flavoured Wafer it is listed with baking soda and with disodium diphosphate, a slower acid, a common pairing that spreads the release of gas across mixing and baking.
