Food additives database

E503 – Ammonium carbonates

Green grain dots symbol for safe food additive (E number classification – GREEN level).

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Safety grading GREEN – SAFE

JECFA assigned E503 an ADI (Acceptable Daily Intake) of “not specified,” which means no numerical mg/kg body weight per day limit was considered necessary for its normal use in food. The decision was based on a weight-of-evidence evaluation rather than a single NOAEL (No Observed Adverse Effect Level) or LOAEL (Lowest Observed Adverse Effect Level). Direct compound-specific data were limited, but a 5-week rat study with 5% ammonium carbonate in the diet found depressed growth and increased blood urea nitrogen, while the broader evidence base showed that the ammonium and bicarbonate parts are normal physiological metabolites and that food-use exposure is far below levels that disturb acid-base balance. On that basis, JECFA concluded that ordinary dietary exposure from additive use did not present a toxicological hazard.

The main caveat is technological rather than toxicological. E503 is used mostly in dry baked goods, where it breaks down during heating and helps create a light, crisp texture. In those products, recipe design and oven conditions matter because ammonium bicarbonate can influence the formation of heat-generated compounds such as acrylamide, even though that does not make E503 itself a high-risk additive at permitted use levels. Studies in biscuits and bread show that ammonium salts can strongly affect texture, flavour chemistry, and process contaminants, so the practical safety question is usually how the finished food is formulated, not whether E503 is inherently dangerous at normal food-use levels (Canali et al., 2020; PMID: 32904002; DOI: 10.1007/s13197-020-04418-1; Haase et al., 2012; PMID: 22784192; DOI: 10.1080/19440049.2012.690349; Faro et al., 2022; PMID: 35954109; DOI: 10.3390/foods11152343).

Side effects

  • No specific side effects are expected at normal food-use levels. The available evidence supports low risk when E503 is used as intended in food.
  • Very high exposure can disturb acid-base balance. That effect is seen in experimental loading studies with related ammonium salts at doses far above ordinary dietary intake.
  • Poorly formulated thick baked goods can retain ammonia odour or taste. This is mainly a quality problem rather than a toxicity signal.
  • Some baked foods made with ammonium bicarbonate can form more acrylamide under certain conditions. That concern depends on the full recipe and baking process, not on E503 alone.

Should You Avoid This Additive?

Most people do not need to avoid E503. It is generally a low-risk raising agent used in small amounts, especially in biscuits, crackers, and similar dry baked goods. Avoidance makes more sense for people who are sensitive to ammonia odours, for those who want to reduce processed snack food. The bigger nutritional issue is usually the product carrying the additive, not E503 itself.

Common Uses

  • Biscuits and cookies. It gives fast lift and helps create a dry, crisp bite.
  • Crackers. It supports expansion without leaving the denser texture common with some other raising agents.
  • Gingerbread and spiced biscuits. Traditional formulas often use baker’s ammonia for texture and spread.
  • Flat bakery items. It works best where gases can escape easily during baking.
  • pH adjustment. Some forms of E503 can also be used as mild acidity regulators.

Common names / Synonyms

  • Ammonium carbonates.
  • Ammonium carbonate.
  • Ammonium bicarbonate.
  • Ammonium hydrogen carbonate.
  • Baker’s ammonia.
  • Baking ammonia.
  • Hartshorn.
  • E503(i).
  • E503(ii).

What is it?

E503 is the collective E-number for ammonium carbonates, a small group of alkaline ammonium salts used mainly as raising agents in baking. In practice, the group covers E503(i) ammonium carbonate and E503(ii) ammonium hydrogen carbonate, which is also widely called ammonium bicarbonate. These compounds release gases when heated, especially ammonia and carbon dioxide, and that is what makes doughs expand. Because the gases escape efficiently from thin, low-moisture doughs, E503 is especially useful in crackers, biscuits, and similar crisp baked products. It is much less suitable for thick cakes or moist breads, where residual ammonia can remain trapped and affect flavour.

Modern food-grade ammonium bicarbonate is typically made from ammonia, carbon dioxide, and water. Food-grade ammonium carbonate is usually a mixture that contains ammonium bicarbonate and ammonium carbamate in varying proportions. Historically, related materials were sold as hartshorn, but current manufacture is controlled and standardized. In baking, E503 is valued because it leaves strong leavening power without adding sodium and can produce a lighter, more open structure than some alternatives (Canali et al., 2020; PMID: 32904002; DOI: 10.1007/s13197-020-04418-1; Sun et al., 2024; PMID: 39296202; DOI: 10.1016/j.heliyon.2024.e37397).

Where it’s allowed (EU vs US)

E503 is authorised in the European Union food additive list as ammonium carbonates. In the United States, ammonium bicarbonate and ammonium carbonate are affirmed as generally recognized as safe direct human food ingredients under 21 CFR 184.1135 and 21 CFR 184.1137, used under current good manufacturing practice.

Further reading