INS 503 (ii) is ammonium hydrogen carbonate, also called ammonium bicarbonate and often known to bakers as baker’s ammonia. It is numbered E503(ii) in Europe. INS 503 covers the ammonium carbonates: (i) is ammonium carbonate and (ii) the hydrogen carbonate. It is made by reacting ammonia with carbon dioxide and water. Codex lists it as an acidity regulator and raising agent.
Its trick is that heat breaks it down completely into ammonia, carbon dioxide and water vapour, so unlike baking soda it leaves no salt behind. In thin, dry products the ammonia escapes during baking, leaving a very crisp, open texture. In thick or moist cakes some ammonia would stay trapped and spoil the taste, so it is kept to small, dry bakes.
That makes it a favourite for crackers and small biscuits, usually together with baking soda, as in Koala’s March biscuits and Campus Choco Puff, as well as Fashion Food’s tomato and paprika crackers.
