Citric acid is an organic acid that is a component of all aerobic living organisms—most abundantly, and not surprisingly, in citrus fruit. This weak acid has been used as an additive in processed foods for more than 100 years as a preservative, a sour flavoring, or an emulsifying agent. Because of its effective preservative properties, citric acid can be found in most canned and jarred foods to prevent botulism.
Known from the eighth century, but first isolated in 1784 by Carl Wilhelm Scheele from lemon juice, industrial scale citric acid production began in the late nineteenth century—made from Italian lemons. World War I interrupted this cycle and an American food chemist, James Currie, discovered a process for making citric acid from mold in 1917. Pfizer started to produce citric acid from molds in 1919.
Citric acid is considered to be a harmless additive by food regulating agencies all over the world. However, public concern has arisen from its erosive effects on tooth enamel.
A small percentage of the population is allergic to citric acid, though the allergy may actually be to trace amounts of corn or black mold that may remain after processing.
There are also questions about what part citric acid plays in acid reflux in infants who eat jarred baby food, much of which is preserved with citric acid. People who have peptic ulcers or other GI sensitivities may experience irritation from citric acid.