Fumaric Acid, as a food additive, it is used as an acidity regulator and is denoted by the E number E297. Fumaric acid is a food acidulent used since 1946. It is generally used in beverages and baking powders for which requirements are placed on purity.
It is generally used as a substitute for tartaric acid and occasionally in place of citric acid, at a rate of 1.36 g of citric acid to every 0.91 grams of fumaric acid to add sourness, similar to the way malic acid is used. It is also used as a coagulant in stovetop pudding mixes.