Citric acida colorless translucent crystalline acid, C6H8O7, principally derived by fermentation of carbohydrates or from lemon, lime, and pineapple juices and used in preparing citrates and in flavorings and metal polishes.
Today, essentially all of the commercial citric acid is produced by surface or submerged fermentation by mold (Aspergillus niger) and submerged fermentation by yeast (Candida guilliermondii, C. lipolytica), using a variety of substrates including sucrose, molasses, corn syrup, enzyme-treated starch, and normal paraffins.