E503 - Ammonium carbonates
What it is and how it is used
Ammonium carbonates — E 503(i) ammonium carbonate and E 503(ii) ammonium hydrogen carbonate — are the oldest chemical raising agents in European baking, known to bakers as hartshorn or baker's ammonia. The name is literal: the original material was distilled from deer antler.
What distinguishes them from bicarbonate is that they need no acid partner. Heat alone splits them completely into ammonia, carbon dioxide and water — three gases, all of which escape. Because nothing is left behind, they raise a biscuit without the residual salty note bicarbonate can leave, and because the ammonia has to be able to escape they only work in thin, dry, low-moisture baking. Used in a cake, the ammonia would be trapped in the crumb and the result would smell of it.
Foods commonly containing it
Crisp biscuits, crackers, gingerbread, Scandinavian and German Christmas baking (lebkuchen, speculaas, pepparkakor), and some flat wafers.
Safety summary
Ammonium carbonates are authorised in Great Britain as E 503 and sit in Group I, permitted at quantum satis.
No numerical ADI has been assigned. The practical reason is unusual and worth stating: the additive does not survive baking. It decomposes completely in the oven and the products leave the biscuit as gas, so essentially none reaches the person eating it.