Citric acid is a white, crystalline organic compound with the chemical formula C₆H₈O₇. As a strong acid, citric acid is widely used in industry and daily life. It is found in almost all plants and in the body fluids of many animals. It is especially abundant in citrus fruits. Citric acid was first isolated from lemon juice in England in 1784.
Chemical and Physical Properties of Citric Acid:
- Molecular Weight: 210.14 g/mol
- Melting Point: 153 °C
- Boiling Point: 175 °C
- Density: 1.66 g/mL
- Solubility: Highly soluble in water and alcohol, low solubility in ether
- pKa Values: -3.1, 4.7, and 6.4
Production Methods of Citric Acid:
- Isolation from Natural Sources: This is the most natural production method of citric acid. It is obtained by pressing fruits rich in citric acid, such as citrus fruits, and evaporating the juice.
- Biochemical Synthesis: This is the most common production method of citric acid. It is produced by fermenting sugary solutions with mold fungi such as Aspergillus niger. Carbon dioxide and water are also byproducts of this process.
- Microbial Fermentation: This is an alternative production method of citric acid. Yeasts such as Candida albicans produce citric acid by utilizing substrates like glucose or molasses.
Applications of Citric Acid:
- Food Industry: Citric acid is one of the most widely used additives in the food sector. It is used to add sour flavor, regulate acidity, stabilize color, prevent oxidation, and extend shelf life. For example, citric acid is used in products such as jams, canned goods, confectionery, frozen foods, fruit juices, carbonated beverages, and instant teas.
- Pharmaceutical Industry: Citric acid is also used in the pharmaceutical sector for various purposes. It is used to increase the solubility of drugs, prepare buffer solutions, and act as an antacid.
- Cosmetic Industry: Citric acid plays an important role in the cosmetic industry. It is used as a moisturizer, exfoliant, and pH regulator in skincare products. It is also used in hair care products to add shine and preserve color.
- Cleaning Industry: Citric acid is effectively used in the cleaning sector. It is used to remove rust from metal surfaces, clean lime scale, and eliminate bad odors.
- Disinfectant Industry: Citric acid is also used in the disinfectant sector. It is used to kill bacteria and viruses, prevent infections, and clean wounds.