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E337AcidulantLow concern
Sodium Potassium Tartrate
In plain words
The short version
Rochelle salt — a mixed-cation tartrate buffer; also famous for its piezoelectric crystals.
Why it's green
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
EFSA (2020) set a group ADI of 240 mg/kg body weight per day for L(+)-tartaric acid and tartrates (E 334–337, E 354), expressed as tartaric acid, and withdrew the earlier EU ADI of 30 mg/kg body weight per day (SCF, 1990). JECFA's ADI (1973) is 0–30 mg/kg body weight, expressed as L(+)-tartaric acid. Same safety profile as the other tartrate salts. Mild laxative at high doses, like other tartrates.
The detail
Discovered in 1675 by Pierre Seignette of La Rochelle, France (the historic name). Produced by neutralizing tartaric acid with mixed sodium and potassium hydroxides. The crystalline form is famously piezoelectric — used in early phonograph pickups and pressure sensors.
Used as a buffer in processed cheese (where the mixed-cation form gives a softer melt than pure sodium or potassium citrate), in jellies, and in instant puddings. Outside food, the Fehling and biuret reagents for sugar and protein assays use Rochelle salt to keep copper soluble in alkali.
Colorless crystalline powder, very soluble in water. Mildly alkaline solution. Hygroscopic. Forms piezoelectric crystals when grown slowly.
In the EU, since 16 December 2024 (Regulation (EU) 2024/1451), tartaric acid and tartrates (E 334–337, E 354) are no longer in the quantum satis Group I. Authorisations in food categories for which industry provided no use data were withdrawn, and numerical maximum levels were set for categories where use data were provided. In the US, sodium potassium tartrate is GRAS for cheeses and for jams and jellies, at levels set by good manufacturing practice (21 CFR 184.1804).
Sources
- EFSA — Re-evaluation of L(+)-tartaric acid (E 334), sodium tartrates (E 335), potassium tartrates (E 336), potassium sodium tartrate (E 337) and calcium tartrate (E 354) as food additives (EFSA Journal 2020;18(3):6030) — European Food Safety Authority (EFSA), 2020. Group ADI 240 mg/kg bw/day (as tartaric acid), replacing the 30 mg/kg ADI
- WHO JECFA database — Potassium sodium L(+)-tartrate (INS 337), evaluation 1973 — Joint FAO/WHO Expert Committee on Food Additives (JECFA), 1973. JECFA ADI 0–30 mg/kg bw (as L(+)-tartaric acid); synonyms Rochelle/Seignette salt
- EUR-Lex — Commission Regulation (EU) 2024/1451 on tartaric acid and tartrates (E 334–337, E 354), applicable from 16 December 2024 — European Union (EUR-Lex), 2024. Removal from quantum satis Group I; numerical maximum levels; withdrawal of unused authorisations
- eCFR — 21 CFR 184.1804 Sodium potassium tartrate (GRAS) — U.S. Government Publishing Office / FDA (eCFR), 1983. US GRAS status: cheeses and jams/jellies at GMP levels
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.