E336i - Monopotassium tartrate

Monopotassium tartrate is cream of tartar — and unusually among the numbered additives, it is a genuine by-product of winemaking. Tartaric acid occurs naturally in grapes; during fermentation its potassium salt crystallises out on the inside of the vat as a hard crust called argol, which is then purified into the white powder sold to bakers.

In the kitchen it does three jobs. As the acid half of baking powder it reacts with bicarbonate to raise a cake. Whisked into egg whites it stabilises the foam so a meringue holds. Added to a sugar syrup it inverts some of the sucrose, which stops boiled sweets and icings crystallising into grit.

Baking powder and self-raising flour, meringues and royal icing, boiled sweets and fondant, some wines and grape products, and home-made playdough.

Potassium tartrates are authorised in Great Britain as E 336 and sit in Group I, permitted at quantum satis. Monopotassium tartrate is specified as E 336(i).

EFSA re-evaluated the tartrates in 2020 and set a group ADI of 240 mg per kg of body weight per day, expressed as tartaric acid, for E 334–337 and E 354. Estimated exposure did not exceed that figure in any population group. The Panel was able to use an unusually small uncertainty factor of 10 rather than the default 100, because human data showed lower internal exposure than in rats.

• FSA Register of Food Additive Authorisations — E 336
• EFSA (2020), 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)
• Assimilated Regulation (EU) No 231/2012 (specifications, E 336(i))