E503: Ammonium Bicarbonate (Baker's Ammonia / Hartshorn)

Direct Answer

E503 (Ammonium Bicarbonate / (NH4)HCO3) is a historic chemical leavening salt. INS 503(ii), ADI is Not Limited (Quantum Satis), decomposing 100% into gaseous CO2, ammonia, and water at temperatures >60°C to create ultra-crisp, airy crackers and cookies.

Source: Codex Alimentarius / EFSA · Last reviewed Aug 28, 2026

Specs

E-Number Code	E503
INS / Codex Number	INS 503(ii)
Functional Class	Raising Agent, Acidity Regulator
Acceptable Daily Intake (ADI)	Not Limited (Quantum Satis)
Chemical Formula	(NH4)HCO3
Primary Mechanism	Thermal decomposition leaves zero residual water or alkali salts: (NH4)HCO3 -> NH3(g) + CO2(g) + H2O(g)
Common Target Foods	Thin crispy crackers, Italian biscotti, Greek koulourakia, sugar wafer shells
Dietary Compliance	Vegan (Mineral synthesis), Halal, Kosher
Safety Approval	EFSA Authorized / FDA GRAS (21 CFR 184.1137)

Why Baker's Ammonia Yields Supreme Crispness

Because both ammonia (NH3) and CO2 evaporate completely as hot gases during baking, E503 leaves no residual water or metallic sodium ions behind, producing an incomparably porous, feather-light, crispy cracker snap.