Principle of sodium citrate as a preservatives

Adjust the pH of food

Sodium citrate is a kind of weak acid and strong alkali salt, with good pH regulation and buffering properties, it can be used with citric acid to form a strong pH buffer. Most microorganisms can grow and reproduce only in specific acid and alkaline environment. By adjusting the pH of food, it can make it deviate from the pH range suitable for microorganisms to grow, so as to inhibit microorganisms' growth and reproduction and achieve the purpose of preservation. For example, by adding sodium citrate to some foods, the pH of the food can be controlled in an interval that is unfavorable to the survival of microorganisms.

Complexation of metal ions

Sodium citrate has good complexing ability for metal ions such as Ca²⁺ and Mg²⁺, and also for other metal ions such as Fe²⁺ ions. Metal ions play an important role in the growth and metabolic process of microorganisms, such as participating in the regulation of enzyme activity. By complexing these metal ions, sodium citrate prevents microorganisms from obtaining enough metal ions to maintain normal physiological activities, thus inhibiting microbial growth and realizing antiseptic effect. For example, in some beverages, sodium citrate can prevent microorganisms from multiplying rapidly due to the presence of metal ions by complexing metal ions.

Influence on microbial metabolism

Sodium citrate can interfere with microbial metabolic pathways to some extent. It may affect the enzyme activity in microbial cells and hinder their normal processes of material and energy metabolism. When the metabolism of microorganisms is inhibited, their growth and reproduction will slow down or even stop, thus prolonging the shelf life of food. However, more in-depth studies are needed to further clarify the specific mechanism of action in this regard.