Sodium citrate

Sodium citrate is used as a flavoring agent and stabilizer in the food and beverage industry; as an anticoagulant, expectorant, and diuretic in the pharmaceutical industry; in the detergent industry, it can replace sodium tripolyphosphate as an additive in non-toxic detergents; chemically, it is an excellent chelating/complexing agent, and its industrial applications leverage this property. It is also used in brewing, injections, photographic chemicals, and electroplating.

Sodium citrate is currently the most important citrate, primarily produced by fermenting starchy materials to generate citric acid, which is then neutralized with alkaline substances. It possesses the following excellent properties: (1) Safety and non-toxicity. Since the raw materials for preparing sodium citrate are largely derived from grains, it is absolutely safe and reliable, posing no harm to human health. The FAO and WHO impose no daily intake restrictions, deeming it non-toxic. (2) Biodegradability. After being diluted by large amounts of water in nature, sodium citrate partially converts into citric acid, with both coexisting in the same system. Citric acid in water easily undergoes biodegradation through the action of oxygen, heat, light, bacteria, and microorganisms. Its decomposition pathway typically involves aconitic acid, itaconic acid, and citraconic anhydride, eventually transforming into carbon dioxide and water. (3) Metal ion complexation ability. Sodium citrate has excellent complexation capabilities for metal ions such as Ca²⁺ and Mg²⁺, as well as for other metal ions like Fe²⁺. (4) Excellent solubility, which increases with water temperature. (5) Good pH regulation and buffering performance. Sodium citrate is a salt of a weak acid and strong base, and when combined with citric acid, it forms a strong pH buffer, making it particularly useful in situations where large pH fluctuations are undesirable. Additionally, sodium citrate also exhibits excellent retarding and stabilizing properties.