E337 - Potassium sodium tartrate

At a glance

This additive keeps foods consistent by tying up metal ions and supporting texture.

• What it is: a tartrate salt also called Rochelle salt
• E‑number: E337
• Main roles: sequestrant (binds metal ions) and stabiliser
• Typical uses: confectionery, syrups, beverages, jams and jellies
• Dietary notes: non-animal origin; suitable for vegetarian and vegan diets
• On labels: “potassium sodium tartrate,” “sodium potassium tartrate,” or “E337”

Why is Potassium sodium tartrate added to food?

Food makers use E337 to control metal ions such as iron and copper that can cause off-colors, off-flavors, or haze. By binding these metals (a function called “sequestration”), the additive helps protect flavor and color and keeps products clearer and more stable. It can also act as a stabiliser, helping a formula hold together during processing and storage. In the European Union (EU), it is an authorised additive with an E‑number and defined specifications.¹ It is listed as an approved additive under the EU’s food additive framework law.²

What foods contain Potassium sodium tartrate?

You may find E337 in sugar-rich and liquid products where clarity and color matter, or where mineral control helps texture. Examples include:

• Flavored syrups and cordial concentrates
• Soft drinks and powdered beverage mixes
• Confectionery (such as fondants and caramels)
• Jams, jellies, and dessert toppings Under EU law, its use is authorised only in certain food categories and at levels set by regulation or by “quantum satis” (use only as much as needed for the effect).²

What can replace Potassium sodium tartrate?

Depending on the recipe, formulators may swap in other sequestrants or acidity regulators:

• Organic acids and their salts, such as citric acid or sodium citrates (including disodium citrate and trisodium citrate)
• Phosphate systems like sodium phosphates or polyphosphates
• Chelating agents for tough metal control, such as calcium disodium EDTA The best substitute depends on pH, flavor impact, labeling goals, and the target metals in the food.

How is Potassium sodium tartrate made?

E337 is the double salt of L(+)-tartaric acid with potassium and sodium. Industry produces it from L(+)-tartaric acid and suitable sodium and potassium sources, then crystallises and dries it to meet purity specifications set in EU law.¹ It is also known in chemistry as “Rochelle salt,” a widely used synonym.³

Is Potassium sodium tartrate safe to eat?

Regulators assess food additives for safety before approval. In the EU, potassium sodium tartrate is authorised under the general food additive regulation and must meet strict identity and purity criteria.²¹ Only the L(+)-tartaric acid form (the natural optical form) is permitted for food use in the EU.¹ As with any additive, manufacturers are required to use no more than is needed to achieve the intended technical effect.²

Does Potassium sodium tartrate have any benefits?

Its benefits are technological, not nutritional. By tying up metal ions, E337 can:

• Protect flavor and color during shelf life
• Help keep beverages and syrups clear
• Support stable texture in sweets and spreads These effects can reduce quality loss without adding noticeable taste at typical use levels.

Who should avoid Potassium sodium tartrate?

Most people do not need to avoid E337 when it is used as intended. However:

• People on medically advised low-sodium or low-potassium diets should consider the small contribution from this salt
• Individuals who must avoid specific tartrates for personal reasons should check labels If you have a kidney, heart, or blood pressure condition requiring mineral restriction, ask a healthcare professional about your total sodium and potassium intake.

Myths & facts

• Myth: It’s the same as cream of tartar. Fact: Cream of tartar is potassium bitartrate (monopotassium tartrate), while E337 is the mixed sodium–potassium salt.
• Myth: It’s an artificial sweetener. Fact: E337 is not a sweetener; it is a sequestrant and stabiliser.
• Myth: “Rochelle salt” means it isn’t food-grade. Fact: Rochelle salt is simply a common name for potassium sodium tartrate; food-grade material must meet official specifications.¹³
• Myth: All tartaric acid salts are interchangeable. Fact: Different tartrates (for example, L(+)-tartaric acid, monopotassium tartrate, or dipotassium tartrate) have different properties and allowed uses.

Potassium sodium tartrate in branded foods

On ingredient lists, look for “potassium sodium tartrate,” “sodium potassium tartrate,” “Rochelle salt,” or “E337.” You’re most likely to see it in beverages, syrups, confectionery, and fruit spreads where color and clarity are important. If you are tracking sodium or potassium, compare serving sizes and consider your full diet.

References

Footnotes

1. 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/eli/reg/2012/231/oj ↩ ↩² ↩³ ↩⁴ ↩⁵

2. Regulation (EC) No 1333/2008 of the European Parliament and of the Council on food additives — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2008/1333/oj ↩ ↩² ↩³ ↩⁴

3. Potassium sodium tartrate — PubChem, National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/Potassium-sodium-tartrate ↩ ↩²