Citric acid (CA), also known as citric acid, with the molecular formula C₆H₈O₇, is an important organic acid. It appears as colorless crystals, odorless, has a strong sour taste, and is easily soluble in water. It naturally exists in fruits such as lemons and citrus, and is currently mainly artificially produced through microbial fermentation. It is widely used in industries such as food, medicine, chemical, and cosmetics.
Citric acid (CA), also known as citric acid, with the molecular formula C₆H₈O₇, is an important organic acid. It appears as colorless crystals, odorless, has a strong sour taste, and is easily soluble in water. It naturally exists in fruits such as lemons and citrus, and is currently mainly artificially produced through microbial fermentation. It is widely used in industries such as food, medicine, chemical, and cosmetics.
The working principle of citric acid is mainly based on its role as an intermediate in the citric acid cycle (also known as the tricarboxylic acid cycle or Krebs cycle) in biochemistry. This cycle is a common metabolic pathway in aerobic organisms, used to store the energy produced by the breakdown of carbohydrates, fats, and proteins in the form of ATP.
In the citric acid cycle, citric acid serves as a bridge connecting oxidation and reduction reactions. Through a series of enzyme catalyzed reactions, citric acid can be converted into other organic acids and release energy. In this process, citric acid plays a crucial role as both a reactant and a product.
| Project indicators | Indicator requirements | Project indicators | Indicator requirements |
| Exterior | White crystalline powder | Oxalate | ≤0.01% |
| Odor | Tasteless | Chloride | ≤0.005% |
| Easy carbide | ≤1.0 | Iron | ≤5.0ppm |
| Water content | 0.5-9.0% | Arsenic | ≤1.0ppm |
| Sulphated ash | ≤0.05% | Lead | ≤0.5ppm |
1. Physical properties
Solubility: Easy to dissolve in water (with a solubility of about 59g/100mL at 20 ℃) and ethanol, slightly soluble in ether, and the aqueous solution is acidic.
Moisture absorption: Anhydrous citric acid easily absorbs moisture in air, while crystalline hydrates can lose their water of crystallization in dry air.
Crystal form: Depending on the crystallization conditions, anhydrous citric acid or citric acid containing crystal water (such as monohydrate citric acid C₆H₈O₇・H₂O) can be obtained.
2. Chemical properties
Acidity: As a tricarboxylic acid, it has strong acidity and can react with bases to form citrate salts (such as sodium citrate, potassium citrate, etc.).
Chelability: capable of forming stable chelates with metal ions (such as Ca²⁺、Fe³⁺), commonly used for removing metal ions or adjusting solution pH.
Reductability: Under specific conditions, oxidation-reduction reactions can occur, but their reducibility is weak, mainly characterized by acidity and chelation.
3. Application Features
Food industry: used as an acidifier, preservative, antioxidant, in beverages, jams, candies, etc., to improve taste and extend shelf life.
Pharmaceutical industry: used for preparing oral and injection
solutions (such as adjusting pH), or as anticoagulants (such as sodium citrate for blood preservation).
Chemical/daily chemical industry: used for detergents (replacing phosphate chelated metal ions), cosmetics (adjusting pH value), electroplating solutions, etc.
In the industrial field, it is used as a scale cleaning agent (such as boiler descaling), metal cleaning agent, leather processing aid, etc.
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