Natural citric acid is widely distributed in nature, and it exists in the fruits of plants such as lemons, citrus fruits, pineapples, as well as in the bones, muscles, and blood of animals. Artificially synthesized citric acid is produced by fermenting sugar containing substances such as sugar, molasses, starch, and grapes.

Many types of fruits and vegetables, especially citrus fruits, contain a high amount of citric acid, especially lemon and lime - they contain a large amount of citric acid, and after drying, the content can reach 8% (the content in fruit juice is about 47 g/L). In citrus fruits, the content of citric acid ranges from 0.005mol/L for oranges and grapes to 0.30mol/L for lemons and limes. This content varies with the growth of different cultivated species and plants