A natural, widely occurring, plant acid, giving the strong tart taste and the characteristic flavour to acidic fruits such as grapes, lemons and oranges. In fruit it can be free or either combined with potassium, calcium or magnesium. Sometimes deposited as crystals in wine.

A dicarboxylic acid, also called dihydroxybutanedioic acid, the free acid was first isolated in 1769 by Carl Wilhelm Scheele, although, in a partially purified form tartar was known to the ancient Greeks and Romans.

Most L-tartaric acid is manufactured as a by-product of the wine industry. The sediments, and other waste products from fermentation are heated and neutralised with calcium hydroxide and then the precipitated calcium tartrate is treated with sulphuric acid to produce free tartaric acid. Can also be extracted from tamarind pulp.

Tartaric acids and the common tartrate salts are all colourless, crystalline solids readily soluble in water.

In food it is used as: an antioxidant where as a synergist it increases the antioxidant effect of other substances: for adjusting acidity in frozen dairy products, jellies, bakery products, dried egg whites, sweets, beverages, jams and preserves and wine: diluting food colours: as a sequestrant, chemically combining with undesirable oxidants and rendering them inactive: an acid in some baking powders.

Can also be found in cocoa powders, sweets and tinned asparagus, fruit and tomatoes.

Eighty per cent of ingested tartaric acid is destroyed by bacteria in the intestine, with the fraction that is absorbed into the bloodstream being excreted in the urine.

Large amounts can cause gastro-enteritis. No known adverse effects in small quantities.