Citric acid is a weak organic acid naturally occurring in citrus fruits and playing a central role in the citric acid cycle (Krebs cycle) for cellular energy production. It is widely used as a food additive for flavoring, preservation, and pH adjustment, as well as in pharmaceuticals, cosmetics, and cleaning products. Chemically, it features three carboxylic acid groups and one hydroxyl group, conferring high water solubility and chelating properties for metal ions. It appears as a white crystalline powder with a sour taste and is produced industrially via fermentation of sugars by Aspergillus niger. Its buffering capacity and antioxidant effects make it valuable in food science and biochemistry.