E366 - Potassium fumarate

At a glance

• What it is: The potassium salt of fumaric acid, used to control acidity and add a clean, tart taste.
• What it does: Stabilizes pH, supports flavor, and can replace sodium-based acidulants when a low-sodium recipe is needed.
• Where it’s used: Drinks, flavored waters, confectionery, bakery fillings, sauces, and similar foods where gentle tartness and buffering are useful.
• Regulatory status: Listed in the European Union’s Union list of food additives as E366 and subject to purity specifications. ^{1 2}
• Typical alternatives: Fumaric acid, citric acid, malic acid, and other fumarate salts.

Why is Potassium fumarate added to food?

Food makers add potassium fumarate to fine-tune acidity and to give a clean, slightly tart note without the sharper sourness of some other acids. As a buffering agent, it helps keep pH steady so flavor and texture remain consistent over shelf life. In recipes that aim to reduce sodium, the potassium salt can stand in for sodium-based options while providing similar functionality. ¹

What foods contain Potassium fumarate?

You may find potassium fumarate in:

• Beverages and flavored waters
• Confectionery and chewing gum
• Fruit preparations, jams, and dessert toppings
• Sauces, dressings, and pickled products
• Bakery fillings and certain baked goods

Authorized uses and levels are set out in the European Union’s Union list of food additives; always check the ingredient list for “potassium fumarate” or “E366.” ¹

What can replace Potassium fumarate?

Depending on the recipe and target taste:

• For stronger sourness: citric acid or malic acid
• For similar function with different cations: sodium fumarate or calcium fumarate
• For direct acid form: fumaric acid itself
• For pH control in low-sodium formulas: potassium citrates When leavening is needed in baked goods, fumarates can be paired with baking soda like sodium bicarbonate to release carbon dioxide.

How is Potassium fumarate made?

Commercially, potassium fumarate is produced by neutralizing food-grade fumaric acid (E297) with a potassium base, such as potassium hydroxide or potassium carbonate, followed by drying and milling to the required particle size. Its composition and purity (including limits for impurities) must meet the European Union specifications for E366. ²

Is Potassium fumarate safe to eat?

In the European Union, E366 is permitted on the Union list of food additives. Only additives that meet safety requirements and have defined conditions of use are placed on this list, and their purity is laid down in separate specifications. ^{1 2} When used within these rules, potassium fumarate is considered safe for its intended technological purposes.

Does Potassium fumarate have any benefits?

• Technological benefits: Helps control acidity, stabilizes flavor, and can improve product consistency over shelf life.
• Formulation benefits: Offers a sodium-free acidulant choice and can complement other acids to fine-tune taste. It is not intended or marketed as a nutrient supplement, even though it contains potassium.

Who should avoid Potassium fumarate?

• People on potassium-restricted diets: Those with kidney disease or on certain medications may need to limit potassium from all sources; talk with a healthcare provider about total potassium intake from food and additives. ³
• Individuals with specific medical advice to limit acidic foods: Follow your clinician’s guidance.

For others, normal food-use levels are not a problem when consumed as part of a balanced diet.

Myths & facts

• Myth: “Potassium fumarate is a harsh chemical.” Fact: It is a simple food-grade salt of fumaric acid, used in small amounts to adjust pH and taste.
• Myth: “It always makes foods very sour.” Fact: Compared with some acids, fumarates provide a cleaner, less sharp tartness, and buffering moderates the overall acidity.
• Myth: “It’s the same as adding potassium supplements.” Fact: It is used for technology and flavor, not for supplementation; the potassium contribution is usually small.

Potassium fumarate in branded foods

On labels, look for “potassium fumarate” or “E366.” It appears most often in beverages, confections, sauces, and certain bakery items where pH control or gentle tartness is desired. Availability varies by region and brand, so checking the ingredient list is the best way to know if it’s present.

References

Footnotes

1. Commission Regulation (EU) No 1129/2011 establishing the Union list of food additives (amending Annex II to Regulation (EC) No 1333/2008) — EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32011R1129 ↩ ↩² ↩³ ↩⁴

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

3. Potassium Fact Sheet for Health Professionals — NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/ ↩