Potassium Tartrate
The short version
Cream of tartar — the slow acid in classic baking powders.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Crystallizes out of wine during fermentation as a natural by-product (the deposit on the inside of barrels and stoppers). Purified by recrystallization. Cream of tartar is the monopotassium form (KHC4H4O6).
How it's used
The acid component of classic baking powders, where it reacts with bicarbonate (E500) on hydration to release CO2 — a slow, dough-cool leavening. Also stabilizes whipped egg whites and meringues (acidifies and chelates trace metals), prevents sugar-syrup crystallization, and gives angel-food cakes their characteristic texture.
Safety profile
ADI of 0–30 mg/kg body weight (as tartrate, combined with E334). Negligible toxicity; very high doses are laxative. Long history of safe use in home and commercial baking.
Physical & chemical properties
White crystalline powder, sparingly soluble in cold water, more soluble in hot. Mildly acidic. Stable in dry storage.
Regulation worldwide
Permitted globally without restrictive limits.
Educational information only. Not medical or dietary advice.