Fumaric Acid
What it does
Sour flavour, acidity regulator.
How it's made
Synthesised.
Fumaric acid is a sharp-tasting organic acid used to add sourness and to regulate acidity, valued because it is a strong acid that goes a long way and stays stable in dry products such as baking mixes and instant desserts. It occurs naturally in many plants (its name comes from the plant fumitory) and is even a normal intermediate in the body's own energy metabolism.
Industrially it is made from petrochemical raw materials: benzene or butane is oxidised to maleic anhydride, which is converted to maleic acid, and this is then rearranged (isomerised) into fumaric acid using heat and a catalyst. A fermentation route using fungi such as Rhizopus also exists and was historically important, but the synthetic route from maleic anhydride dominates today.
The finished acid is purified and dried into a white powder. Because fumaric acid dissolves slowly in cold water, food-grade grades are often milled to specific particle sizes, and specially treated versions are sold so that it disperses properly in applications like tortillas, fruit drinks and gelatine desserts.
Possible reactions
Generally safe.