Citric acid is a common, naturally occurring compound. Despite its name, citric acid itself is not mold. While a specific type of mold plays a crucial role in its industrial production, the final product is a highly purified substance distinct from the microorganism.
What is Citric Acid?
Citric acid is a weak organic acid with the chemical formula C₆H₈O₇, appearing as a colorless and odorless crystalline solid. It is known for its distinctly sour taste. This compound is a tricarboxylic acid, meaning it possesses three carboxylic acid groups, which contribute to its acidic properties.
Citric acid occurs naturally in many fruits and vegetables. Citrus fruits such as lemons, limes, oranges, and grapefruits contain particularly high concentrations. It is also present in smaller amounts in fruits like pineapples, strawberries, and tomatoes. In living organisms, citric acid is an intermediate in the citric acid cycle, also known as the Krebs cycle, a fundamental metabolic pathway central to cellular respiration.
The “Mold” Connection: Industrial Production
The association of citric acid with mold stems from its primary industrial production method. While citric acid was historically extracted from citrus fruits, this method proved inefficient and costly for large-scale demand. In the early 20th century, researchers discovered that the fungus Aspergillus niger, a common black mold, could efficiently produce citric acid through fermentation.
Today, the vast majority of citric acid is produced using this microbial fermentation process with Aspergillus niger. In this process, the mold metabolizes sugars, such as molasses or corn starch, in a controlled environment. The fungus acts as a “microbial factory,” converting these sugars into citric acid as a metabolic byproduct. After fermentation, the citric acid is rigorously separated and purified from the fungal biomass and other byproducts. This purification ensures the final product is pure citric acid, not the mold itself.
Safety and Regulation of Citric Acid
Citric acid is widely considered safe for consumption and use across various industries. Regulatory bodies around the world, such as the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), classify it as “Generally Recognized As Safe” (GRAS). This designation reflects its long history of safe use and extensive scientific evaluation.
While generally safe, some individuals may experience sensitivities or intolerances, though true allergic reactions to citric acid itself are rare. Any reported reactions are often attributed to residual impurities from the manufacturing process or other components in the food rather than the citric acid molecule. The rigorous purification steps in industrial production are designed to remove any fungal residues, ensuring the final product is highly pure.
Everyday Uses of Citric Acid
Citric acid’s versatile properties make it a widely used ingredient across numerous everyday products. In the food and beverage industry, it functions as a flavoring agent, providing a tart taste to soft drinks, candies, and jams. It also serves as a preservative by lowering pH, which inhibits microbial growth and extends shelf life, and acts as an emulsifier.
Citric acid is a common component in many cleaning products. Its chelating ability allows it to bind with metal ions, making it effective at removing limescale, hard water stains, and soap scum from surfaces. It also contributes to the antibacterial and antifungal properties of some cleaners. In cosmetics and pharmaceuticals, citric acid is used as a pH adjuster, antioxidant, and effervescent agent. Its diverse applications underscore its importance in modern manufacturing.