Citric acid is a common ingredient found in numerous products, including foods, beverages, cleaning agents, and cosmetics. Its widespread presence often leads to questions about its origins, particularly whether it comes from mold. This article explores the methods used to produce citric acid and addresses concerns regarding its safety and natural counterparts.
The Fungal Factory
The vast majority of citric acid, about 99% of the world’s supply, originates from a biological process involving specific fungi. This industrial method relies primarily on the mold Aspergillus niger, cultivated under controlled conditions. These fungi are fed a sugar-rich medium, often derived from inexpensive sources like molasses, corn syrup, or hydrolyzed corn starch.
Within large bioreactors, Aspergillus niger metabolizes these sugars, converting them into citric acid as a metabolic byproduct. This process is an efficient, scalable fermentation, differing significantly from uncontrolled mold growth on food. This fungal fermentation method became widespread after American food chemist James Currie discovered Aspergillus niger’s efficiency in 1917, leading to industrial production by Pfizer by 1919. This biotechnological approach quickly surpassed traditional extraction from citrus fruits due to its cost-effectiveness and ability to meet growing global demand.
Ensuring Safety and Purity
Despite its fungal origin, the citric acid found in commercial products undergoes rigorous purification processes, ensuring it is safe for consumption and use. After fermentation, the fungal material is separated from the liquid containing citric acid. The solution then proceeds through several purification stages, including filtration, precipitation as calcium citrate, and subsequent conversion back into pure citric acid using sulfuric acid. Further steps like decolorization and crystallization yield the final, highly pure product.
The U.S. Food and Drug Administration (FDA) has affirmed citric acid as “Generally Recognized As Safe” (GRAS) for use as a direct food additive. This designation signifies that experts consider it safe under its intended conditions of use. The widespread incorporation of citric acid into countless food, beverage, pharmaceutical, and cosmetic items further underscores its established safety profile, with the mold itself being entirely absent from the pure final product.
Natural Versus Industrial Citric Acid
The citric acid molecule produced through fungal fermentation is chemically identical to the citric acid found naturally in fruits like lemons and limes. Both forms share the same molecular structure (C₆H₈O₇) and exhibit similar properties, such as being a colorless, weak organic acid with a sour taste. While Carl Wilhelm Scheele first isolated citric acid from lemon juice in 1784, the sheer volume required for modern industrial applications made direct extraction from fruit impractical and expensive.
The transition to industrial fermentation became a necessity to meet global demand efficiently. Consumers can therefore be confident that the citric acid added to their products, regardless of its source, is the same chemical compound. Although natural citric acid may contain trace amounts of other compounds, the industrially produced version is highly purified, offering consistent quality for various applications.