Ammonium carbonates
A leavening salt used in baking. It releases carbon dioxide gas in the oven, making biscuits and crackers rise, then breaks down completely so nothing remains in the finished product.
What is it?
Ammonium carbonates is a group of ammonium salts, principally ammonium bicarbonate and ammonium carbonate, produced by passing carbon dioxide and ammonia gas through water. It appears as a white powder or crystalline solid with a faint ammonia smell. It is also known as baker's ammonia or hartshorn salt, the latter name reflecting its historical origin from the distillation of deer antler.
What does it do?
When heated above roughly 60 degrees Celsius it decomposes into three gases: ammonia, carbon dioxide, and water vapour. All three escape from the dough or batter during baking, leaving no residue in the cooked product. The gas production creates bubbles in the batter matrix that expand in heat and set as the starch and protein cook, giving a light, open crumb structure. Unlike baking powder, it leaves no alkaline or acidic salt residue, so the baked product has a cleaner flavour. It is used in low-moisture products such as biscuits, crackers, and flatbreads where the thin cross-section allows all the ammonia to escape fully during baking.
Where you will see it
Dry biscuits, crackers, cream crackers, rich tea biscuits, shortbread variants, gingerbread, amaretti, speculoos spiced biscuits, and some traditional flatbreads and wafers. In baked goods with a thick cross-section (cakes, bread loaves) the ammonia cannot escape fully and the product retains an off-flavour, so its use is confined to thin, dry items. On a UK ingredient label it appears as ammonium carbonates, ammonium bicarbonate, raising agent (E503), or raising agent (503).
What the science says
Complete decomposition during baking
The defining technical characteristic of E503 is that it decomposes entirely into gases (ammonia, carbon dioxide, water) at baking temperatures, leaving no ionic residue in the finished food. This distinguishes it from sodium-based leaveners and means the body is not exposed to ammonium salts from the finished product. Dietary exposure to the additive itself is therefore negligible.
Ammonium bicarbonate decomposes completely above approximately 60 degrees Celsius into ammonia gas, carbon dioxide, and water; no ammonium salt persists in properly baked, low-moisture products.
EFSA re-evaluation and acceptable daily intake
As part of the mandatory re-evaluation of all pre-2009 food additives, the European Food Safety Authority assessed ammonium carbonates in 2018. The panel concluded that there was no concern at the levels used in food. No numerical ADI was set because dietary exposure through food was considered to be minimal given the complete decomposition at baking temperatures. The panel found no evidence of genotoxicity or carcinogenicity.
EFSA's ANS panel concluded there was no safety concern from the use of ammonium carbonates as a food additive at current permitted levels; no numerical ADI was considered necessary given negligible residual exposure.
Ammonia and normal metabolism
Ammonia is a normal metabolite in human biochemistry, produced in the gut during protein digestion and detoxified in the liver as part of the urea cycle. The trace quantities of ammonia gas that could theoretically remain in food from E503 are far below those generated endogenously from dietary protein. Toxicological studies on ammonium salts have not identified reproductive, developmental, or organ-specific effects at realistic food-use levels.
Ammonia is an endogenous metabolite present in human tissues; the liver converts it to urea continuously, and dietary exposure from ammonium salt residues in food is small relative to endogenous production.
Where it stands with the regulators
Who should be careful
People with severe ammonia-metabolism disorders (such as urea cycle disorders) are sometimes advised by their clinician to limit ammonium intake from all sources, though residual ammonium from baked goods is very small. There are no allergen declarations required for E503 under UK food law. Anyone instructed by a doctor to restrict ammonium intake should check with their healthcare team about biscuits and crackers that list raising agent (E503) or ammonium bicarbonate in the ingredients.
The honest read
Ammonium carbonates is one of the oldest leavening agents in European baking, predating baking powder by centuries. The science is straightforward: it decomposes in the oven and nothing remains in the finished biscuit or cracker. EFSA reviewed it formally in 2018 and found no reason to set a numerical limit or restrict its use. The main practical question is whether the ammonia escapes fully during baking, which depends on the product being thin and dry enough. In correctly made biscuits and crackers it does. There is no live scientific debate about this additive.
Related additives
Common questions
Is E503 banned in the UK?
No. E503 (ammonium carbonates) is approved for use in the UK under the UK FSA's approved-additives list, which has retained this authorisation since the UK left the EU. It remains permitted across Great Britain.
Does ammonia end up in the food I eat?
In properly baked, thin, dry products such as biscuits and crackers, the ammonia generated during baking escapes as a gas and is not present in the finished food. EFSA confirmed this in its 2018 re-evaluation. The additive is not used in thick, moist products like bread loaves because the ammonia cannot escape fully, which affects the taste rather than safety.
What foods contain E503?
Dry biscuits, cream crackers, rich tea biscuits, gingerbread, amaretti, speculoos, wafers, and similar thin baked goods. Check the ingredients list for ammonium carbonates, ammonium bicarbonate, or raising agent (E503).
Is E503 vegan?
Yes. Ammonium carbonates is synthesised from ammonia and carbon dioxide; it contains no animal-derived ingredients and is suitable for vegans.
Sources
- FSA Regulated Products Database: E503 Ammonium Carbonates
- FSA Approved Additives and E Numbers
- EFSA ANS Panel: Re-evaluation of ammonium carbonates (E 503i, E 503ii) as food additives, EFSA Journal 2018
- Assimilated Regulation (EC) No. 1333/2008 on food additives, Annex II
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
See this on every food you scan
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
Get NutraSafe on the App Store