E-numbers / Acidity regulators / E337
also: Rochelle salt · Potassium sodium tartrate · Seignette salt
A double salt of tartaric acid, used to control acidity and stabilise texture in jams, confectionery and processed cheese.
Scan a barcode to check a food for sodium potassium tartrate. NutraSafe Pro · £6.99/month · iPhone and Android
Sodium potassium tartrate is a crystalline double salt formed from tartaric acid, a naturally occurring acid found in grapes and other fruits.
UK supermarket foods that declare E337: 13 of the 43,325 we checked (under 0.1%)
Counted by its code or its name in the ingredient list.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Sodium potassium tartrate is a crystalline double salt formed from tartaric acid, a naturally occurring acid found in grapes and other fruits. It is also known historically as Rochelle salt or Seignette salt after the French pharmacist who first prepared it. It occurs as a white, odourless powder.
It acts as an acidity regulator, buffering the pH of food to keep it stable during processing and storage. It also functions as a sequestrant, binding trace metal ions that would otherwise trigger rancidity or colour change. In processed cheese production it works as an emulsifying salt, helping fat and water bind smoothly.
Most commonly found in processed cheese and cheese spreads, jams, jellies and marmalades, chocolate and cocoa-based products, baking powder blends, soft drinks, and some confectionery. On a UK ingredient label it will appear as either 'sodium potassium tartrate' or 'E337'.
Tartaric acid and its salts occur naturally in grapes, wine, tamarinds and bananas. The body absorbs only a small fraction; most passes through unchanged to be broken down by gut bacteria or excreted. This means dietary exposure from the additive is a small addition to a background that already comes from everyday fruit and wine consumption.
Tartaric acid and tartrate salts (E334-337, E354) are metabolised partly by intestinal bacteria and partly excreted; absorbed amounts are low and no accumulation in tissues has been identified at food-use levels.
EFSA completed a full re-evaluation of the tartrate group (which includes E337) in 2020 as part of its systematic review of all approved EU food additives. The panel found no toxicological concern at the levels used in food and did not set a numerical acceptable daily intake, judging the existing approvals to be sound.
EFSA concluded that tartaric acid and its salts, including sodium potassium tartrate (E337), raised no safety concern at current permitted and estimated dietary exposure levels, and no numerical ADI was considered necessary.
In large amounts, tartrate salts can have a laxative effect because unabsorbed tartrate draws water into the colon. This is a well-documented property that was once exploited medicinally. At the levels present in food it is not a practical concern, but products eaten in quantity, such as certain baking powders, could contribute meaningfully to intake.
High oral doses of tartrate salts produce osmotic laxative effects in humans; the threshold is well above realistic dietary exposure from approved food uses.
People advised by a doctor to follow a low-sodium or low-potassium diet may want to note that this additive contributes both minerals. Look for 'sodium potassium tartrate' or 'E337' on the label. Amounts in typical food portions are small, but the label check is relevant for those on clinical dietary restrictions.
Tartrate has been in food and pharmaceutical use for centuries and is one of the most thoroughly reviewed acidity regulators in the EU system. EFSA completed its formal re-evaluation in 2020 and found no new concerns. The main thing to know is that it is a salt of a fruit acid, it performs a real technological function, and the science on it is not contested.
No. E337 is approved under the UK FSA approved-additives list and the assimilated EU Regulation 1333/2008. It is permitted across a wide range of food categories.
Sodium potassium tartrate contributes a small amount of both sodium and potassium. For most people the quantities in food are negligible. People on a medically supervised low-sodium or low-potassium diet should be aware of it and can check labels for 'E337' or 'sodium potassium tartrate'.
Processed cheese and cheese spreads, jams and marmalades, chocolate products, baking powder, confectionery and some soft drinks are among the most common sources.
Yes. Sodium potassium tartrate is produced from tartaric acid, which is typically derived from wine production by-products (grape pomace and lees). It contains no animal-derived ingredients and is considered vegan.
Last reviewed: 20 June 2026
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