Sour taste of ‘Coca Cola’ is due to the presence of

Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas, but not without controversy regarding its health effects. It provides a tangy or sour taste and, being a mass-produced chemical, is available cheaply and in large quantities. The low cost and bulk availability is unlike more expensive seasonings that give comparable flavors, such as citric acid which is obtainable from citrus, but usually fermented by Aspergillusniger mold from scrap molasses, waste starch hydrolysates and phosphoric acid.