E500III - Sodium sesquicarbonate

At a glance

Sodium sesquicarbonate is part of the “sodium carbonates” family (E500), alongside sodium carbonate and sodium bicarbonate.

• What it does: acidity regulator (buffer) and gentle raising agent
• Where it’s used: permitted in many food categories in the EU; label may read “E500iii” or “sodium sesquicarbonate”
• Taste/texture: milder than washing soda (sodium carbonate), steadier than baking soda (sodium bicarbonate)
• Safety: re‑evaluated by the European Food Safety Authority with no safety concern at reported uses
• Sodium: it contributes dietary sodium, so amounts matter for sodium‑restricted diets

Why is Sodium sesquicarbonate added to food?

Food makers use sodium sesquicarbonate to regulate acidity (keep pH steady) and to release carbon dioxide when combined with an acid, which helps batters and doughs rise. Within the EU, it is listed under the sodium carbonates group (E500) for use as an acidity regulator and raising agent.¹²

Compared with its sister salts, sodium carbonate is strongly alkaline, while sodium bicarbonate is milder but less buffering on its own. Sodium sesquicarbonate sits in between, providing a gentle, sustained alkalinity that can fine‑tune browning, tenderness, and flavor in baked goods.²

What foods contain Sodium sesquicarbonate?

You may find E500iii in bakery mixes, crackers, cookies, and other processed cereal products where controlled alkalinity or a mild leavening effect is needed. In the European Union, sodium carbonates (including E500iii) are authorized in a wide range of foods according to Annex II of the food‑additives regulation and must meet purity specifications.¹³

On labels in the EU, it may appear as “E500iii,” “E500(iii),” or “sodium sesquicarbonate.” Outside the EU, it may be grouped simply as “sodium carbonates” alongside E500(i) and E500(ii), depending on local rules.³

What can replace Sodium sesquicarbonate?

Alternatives depend on the job you need done:

• For similar leavening with a bit less alkalinity: sodium bicarbonate used with a suitable acid (for example, citric acid, monocalcium phosphate, or disodium diphosphate).
• For stronger alkalinity or “alkaline treatment” effects (more browning, distinctive flavor): sodium carbonate.
• For reduced sodium formulas: potassium carbonates may play a similar pH‑control role.
• For buffering without leavening gas: sodium citrates or sodium phosphates can act as acidity regulators.

How is Sodium sesquicarbonate made?

Sodium sesquicarbonate is the double salt formed from sodium carbonate and sodium hydrogen carbonate (sodium bicarbonate). Food‑grade material is typically produced by crystallizing it from solutions containing the two salts under controlled conditions, or via processing routes used for the sodium carbonates family.¹²

It is specified in EU law as part of E500, with detailed purity and identity criteria (including limits for contaminants) that manufacturers must meet for food use.¹

Is Sodium sesquicarbonate safe to eat?

The European Food Safety Authority (EFSA) re‑evaluated the sodium carbonates group (E500) and concluded there was no safety concern for their use at reported levels in foods; a numerical Acceptable Daily Intake (ADI) was not deemed necessary.² In the EU, only material meeting the official purity specifications may be placed on the market for use in food.¹

In the United States, closely related ingredients sodium carbonate and sodium bicarbonate are affirmed as Generally Recognized as Safe (GRAS) when used in line with good manufacturing practice.⁴⁵

Does Sodium sesquicarbonate have any benefits?

For food processing, its benefits are mainly technological. It buffers acidity to help stabilize flavor and color, and it acts as a gentle leavening base when paired with suitable acids. This can support even browning and tender textures in baked goods while avoiding the harsh alkalinity of washing soda.²

Who should avoid Sodium sesquicarbonate?

• People limiting sodium: As a sodium salt, it adds to daily sodium intake. Dietary guidance in the U.S. recommends keeping sodium below 2,300 mg per day for most adults; check labels and serving sizes if you are on a sodium‑restricted plan.⁶
• Individuals advised by a healthcare professional to restrict specific salts or buffer additives should follow that guidance.

Myths & facts

• Myth: “E500iii is the same as washing soda.”
  Fact: Washing soda is sodium carbonate (E500i). Sodium sesquicarbonate is a different double salt with milder alkalinity and its own food‑grade specification.¹
• Myth: “Carbonate additives always need an ADI.”
  Fact: EFSA concluded no safety concern for E500 at reported uses and did not set a numerical ADI.²
• Myth: “All forms of E500 are interchangeable.”
  Fact: E500(i), E500(ii), and E500(iii) differ in alkalinity and buffering behavior, so formulators choose among them for specific texture, browning, and flavor targets.²

Sodium sesquicarbonate in branded foods

To spot it on packages, look for “E500iii,” “E500(iii),” or “sodium sesquicarbonate” in the ingredient list. Some products may instead list the broader class “sodium carbonates (E500).” Availability in specific brands varies by country and recipe; baked snacks, mixes, and certain biscuits are common places to look.

References

Footnotes

1. Commission Regulation (EU) No 231/2012 — Specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0231 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

2. Re-evaluation of sodium carbonates (E 500), potassium carbonates (E 501) and ammonium carbonates (E 503) as food additives — EFSA Journal. https://www.efsa.europa.eu/en/efsajournal/pub/5364 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

3. Regulation (EC) No 1333/2008 on food additives — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2008/1333/oj ↩ ↩²

4. 21 CFR §184.1736 — Sodium carbonate; affirmed as GRAS — U.S. FDA. https://www.ecfr.gov/current/title-21/section-184.1736 ↩

5. 21 CFR §184.1768 — Sodium bicarbonate; affirmed as GRAS — U.S. FDA. https://www.ecfr.gov/current/title-21/section-184.1768 ↩

6. Dietary Guidelines for Americans, 2020–2025 — U.S. HHS/USDA. https://www.dietaryguidelines.gov/resources/2020-2025-dietary-guidelines-online-materials ↩