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Views: 0 Author: Site Editor Publish Time: 2026-02-12 Origin: Site
Citric acid is an organic acid widely found in citrus fruits and is one of the most widely used acidulants and acidity regulators in the food industry. Due to its high safety, mild flavor, and stable source, it has wide applications in food, pharmaceuticals, daily chemicals, cleaning agents, and other industrial fields.
Based on the presence or absence of water of crystallization in its molecule, citric acid is mainly divided into two common forms: citric acid monohydrate and anhydrous citric acid.
The core difference between the two lies in the presence or absence of water of crystallization in their chemical structure. This difference exists only in the solid form. When both dissolve in water, they dissociate to release the same citrate ion, therefore their chemical activities are completely identical.
1. Specific differences between citric acid monohydrate and anhydrous citric acid
(1) Differences in molecular structure
Citric acid monohydrate contains one molecule of water of crystallization, and its chemical formula is:
C₆H₈O₇·H₂O
Anhydrous citric acid does not contain water of crystallization, and its chemical formula is:
C₆H₈O₇
Both have the same core chemical components, but due to the presence of water of crystallization, citric acid monohydrate has a slightly higher molecular weight.
(2) Differences in physical properties
In terms of appearance and physicochemical properties, the two exhibit the following differences:
Comparison Items | Citric acid monohydrate | Anhydrous citric acid |
Crystallization Water | Contains one molecule | / |
Appearance | White crystals | white crystals or granules |
Hygroscopicity | Relatively low | Relatively high |
Stability | Stable at low temperatures | More stable at high temperatures |
Dissolution Rate | Slightly slow | Dissolves faster |
Citric acid typically crystallizes in its monohydrate form at temperatures below 36°C; at temperatures above this, it more readily forms anhydrous crystals.
2. Differentiated Applications in the Food Additives Industry
(1) A Clever Choice in the Beverage Industry
Anhydrous citric acid, due to its high purity and consistent acidity, is commonly used in carbonated beverages and fruit juice production. Anhydrous citric acid provides stable and controllable acidity regulation and does not affect product standardization due to changes in the water of crystallization content. For example, globally renowned cola brands often use anhydrous citric acid to ensure consistent taste across their global products.
Monohydrate citric acid, due to its rapid dissolution properties, is frequently used in solid instant beverages. Products such as solid beverages and effervescent tablets utilize monohydrate citric acid to achieve an "instant dissolution in water" effect. Data shows that monohydrate citric acid dissolves in cold water approximately 30% faster than its anhydrous form.
(2) Differences in Applications in Candies and Baked Goods
Citric acid, as an acidity regulator, is frequently added to candies. Anhydrous citric acid is often used in savory soft candies. Due to its low moisture content, it does not easily absorb water, maintaining the dry texture of the candy surface. Citric acid monohydrate is used for adjusting the internal acidity of filled candies because it dissolves quickly and creates a uniform acidity distribution within the candy.
In baked goods, the carbon dioxide produced by the reaction of anhydrous citric acid and baking soda creates uniform pores in cakes and cookies, preventing moisture from affecting the dough's stability.
(3) Preservative Considerations for Canned and Pickled Foods
Citrate monohydrate is often added to canned products. It can more stably maintain pH values and effectively inhibit pathogenic bacteria such as Clostridium botulinum. Anhydrous citric acid is mostly used in pickled foods. Its strong initial acidity effectively prevents spoilage.
3. Key Applications in the Pharmaceutical Industry
(1) Precise Considerations in Formulation Processes
In the pharmaceutical field, the choice between these two forms of citric acid reflects the refinement of formulation science:
Anhydrous citric acid: Injectable and infusion products. Anhydrous citric acid has higher purity and is more stable. It can effectively regulate pH values and enhance drug solubility, thereby ensuring the sterility and stability of the product. In addition, anhydrous citric acid also has hangover relief, anti-fatigue, and antioxidant effects. In recent years, it has been used in functional health product formulations, with an annual market demand growth rate of 4.1%.
Citrate monohydrate: Oral liquid preparations and effervescent tablets and granules. Citric acid monohydrate dissolves rapidly and has moderate buffering capacity, ensuring that the product releases the drug quickly upon contact with water.
(2) Drug Stability and Absorption Promotion
Anhydrous citric acid and monohydrate citric acid exhibit subtle differences in drug stability. In some formulations containing metal ion active ingredients, anhydrous citric acid is used to utilize its metal ion chelating ability to prevent the drug from being oxidized and decomposed. Monohydrate citric acid, due to its buffering properties, can maintain a suitable pH environment in gastric-soluble formulations, promoting the absorption of alkaline drugs.
4. Innovative Applications in the Cosmetics Industry
(1) pH Adjustment in Skincare Products
Citrate monohydrate is commonly used in cleansers, toners, etc. Its mild acidity helps adjust the pH value of skincare products. It has low irritation to the human body and strong cleansing ability.
Anhydrous citric acid is often used in creams, lotions, and other products with a high oil content. It has minimal impact on the stability of the emulsion system, thus offering greater advantages.
(2) Preservative Enhancement and Antioxidant Effects
Citrate acid is not only a pH adjuster in cosmetics but also an important preservative enhancer. Anhydrous citric acid works more effectively when combined with potassium sorbate, expanding the antibacterial spectrum and reducing the total amount of preservatives used. Furthermore, its ability to chelate metal ions helps prevent oil oxidation and extend product shelf life.
(3) Development of Novel Delivery Systems
In recent years, two forms of citric acid have shown unique value in cosmetic nano-delivery systems. Studies have shown that the water of crystallization of citric acid monohydrate can help construct porous microsphere carriers with specific pore sizes, achieving sustained release of active ingredients. Anhydrous citric acid is used to regulate the stability of certain liposome formulations and prevent particle aggregation.
5. Other Industrial Applications
(1) Detergents and Cleaning Products
In household detergents, there is little difference between monohydrate and anhydrous citric acid, mainly because: if both are soluble in water, they are essentially the same product.
Industrial cleaning agents are selected based on specific needs. High-temperature cleaning processes often use anhydrous citric acid, while room-temperature or low-temperature cleaning uses monohydrate citric acid, which dissolves quickly and has higher cleaning efficiency.
(2) Environmental Protection and Water Treatment
In the water treatment field, both forms of citric acid are used as corrosion inhibitors and cleaning agents. Monohydrate citric acid dissolves quickly and has relatively low corrosiveness, making it widely used in medium- and low-temperature boiler cleaning. Anhydrous citric acid is mostly used in high-temperature system cleaning and industrial circulating water treatment.
(3) Construction and Building Materials Industry
In concrete admixtures, anhydrous citric acid is used as a retarder, which can extend the workable time of concrete and is particularly suitable for construction in high-temperature environments. It effectively ensures the stability of concrete strength.
6. How to Choose Between Monohydrate and Anhydrous Citric Acid?
Priority given to dissolution speed: Choose monohydrate citric acid.
Priority given to purity and stability: Choose anhydrous citric acid.
Cost-sensitive, high-volume production: Evaluate the effective cost per unit for both forms.
Storage or use in high-humidity environments: Prioritize anhydrous citric acid.
Requirement for precise acidity control: Anhydrous citric acid is easier to measure accurately.
Environmental friendliness and sustainability: Monohydrate citric acid production processes typically have lower energy consumption.
Conclusion
Both monohydrate and anhydrous citric acid play important roles in various aspects of life. In the future, Polifar will continue to provide high-quality citric acid products globally, offering optimal product support for the robust growth of global businesses. Polifar remains committed to providing excellent service to customers worldwide!
