Citric Acid Anhdrous Food Grade

Melting point: 153 - 159 °C
Boiling point: 309.6 ± 42.0 °C (760 mmHg)
Vapor density: 7.26 (vs air) [3]
Vapor pressure: < 0.1 hPa (20 °C) [3]
Refractive index: 1.493 - 1.509 [1]
Flash point: 155.2 ± 24.4 °C [1]
Solubility: Soluble in water, ethanol, and ether; insoluble in benzene; slightly soluble in chloroform
pH value: 3.24 (1 mM aqueous solution); 2.62 (10 mM aqueous solution); 2.08 (100 mM aqueous solution)

Food Industry
Citric acid is the largest organic acid produced by biochemical methods in the world. Citric acid and its salts are one of the pillar products in the fermentation industry and are mainly used in the food industry as acidulants, solubilizers, buffers, antioxidants, deodorants, flavor enhancers, gelling agents, and colorants, etc. [22].
In terms of food additives, it is mainly used in carbonated beverages, fruit juice beverages, lactic acid beverages, and other refreshing drinks and pickled products. Its demand varies with seasonal and climatic changes. Citric acid accounts for about two-thirds of the total consumption of acidulants. Adding citric acid to canned fruits can maintain or improve the flavor of the fruits, increase the acidity (lower the pH value) of some fruits with lower acidity during canning, weaken the heat resistance of microorganisms and inhibit their growth, and prevent bacterial spoilage and bulging of canned fruits with lower acidity. Adding citric acid as an acidulant in candies makes it easier to coordinate with fruit flavors. Using citric acid in gel foods such as jams and jellies can effectively reduce the negative charge of pectin, allowing pectin molecules to combine through hydrogen bonds and form gels. In the processing of canned vegetables, some vegetables have an alkaline reaction. Using citric acid as a pH adjuster not only serves as a flavoring agent but also helps maintain their quality. The chelating ability and pH adjustment properties of citric acid make it effective in increasing the performance of antioxidants, inhibiting enzyme activity, and extending the shelf life of frozen foods [23].
Metal Cleaning
Citric acid is an organic acid produced through microbial fermentation and is widely used in detergent production. Its specific properties and chelating ability play a positive role. In practical use, citric acid demonstrates excellent performance, especially in terms of safety. The raw materials for preparing citric acid are all derived from food grains, which are safe food-grade microorganisms. The use of citric acid does not affect the environment and is easily degraded under the action of microorganisms and heat. Its chelating ability is also strong, especially the chelating ability of citrate salts to manganese and iron ions, and the usage effect is also prominent. The corrosion inhibition performance of citric acid in detergents is also outstanding. As an important part of chemical cleaning, acid washing, compared with inorganic acids, citric acid has relatively weak acidity and thus causes less corrosion to equipment. Citric acid cleaning is safe and reliable, and the waste liquid is easy to handle and does not pose a threat to human health [24].
(1) Mechanism of Citric Acid Cleaning
Citric acid causes less corrosion to metals and is a safe cleaning agent. Since citric acid does not contain Cl-, it will not cause stress corrosion of equipment. It can chelate Fe3+ and weaken the promoting effect of Fe3+ on corrosion.
Citric acid can dissolve iron oxide and copper oxide, forming citric acid-iron and citric acid-copper complexes. If an ammonia-citric acid solution is used, it can form highly soluble complexes such as ammonium ferrous citrate and ammonium ferric citrate, resulting in excellent cleaning effects. Citric acid is mainly used for rust removal, so it is mainly used to clean newly built boilers. When mixed with sulfamic acid, glycolic acid, or formic acid, it can be used to clean calcium and magnesium scale and rust in boilers. When mixed with ethylenediaminetetraacetic acid (EDTA), it can be used to clean superheaters [5].
Citric acid and its derivatives, with their unique physical and chemical properties, have broad applications in many fields such as chemical cleaning.
(2) Citric Acid Cleaning of Pipes
This is the latest cleaning technology for high-impurity hard water. It uses food-grade citric acid to soften stubborn scale, and then uses microcomputer-controlled water flow and pneumatic pressure to generate water flow oscillation, causing the accumulated scale in the pipes to peel off and fall off, making the pipes unobstructed and clean [3].
(3) Cleaning Gas Water Heaters with Compound Surfactants Chemical cleaning agents composed of citric acid, AES and benzotriazole can be used to clean gas water heaters that have been in use for many years. The cleaning agent is injected into the upside-down water heater and soaked for 1 hour. Then, the cleaning solution is drained and the heater is rinsed thoroughly with clean water before being used again. Under the same flow rate, the outlet water temperature can be increased by 5℃ to 8℃ [5].

(4) Cleaning water dispensers
Dilute edible citric acid (powder form) with water and inject it into the heating tank of the water dispenser. Soak for about 20 minutes. Finally, rinse the tank repeatedly with clean water until it is clean. It is non-toxic and effective [5].

Fine Chemical Industry
Citric acid is a type of fruit acid that can accelerate the renewal of keratin and is commonly used in lotions, creams, shampoos, whitening products, anti-aging products, and acne products. In chemical technology, citric acid can be used as an experimental reagent, chromatographic analysis reagent, and biochemical reagent; as a chelating agent and masking agent; and to prepare buffer solutions. Using citric acid or citrate as a detergent additive can improve the performance of washing products, quickly precipitate metal ions, prevent contaminants from reattaching to fabrics, maintain the necessary alkalinity for washing; disperse and suspend dirt and ash; and enhance the performance of surfactants. It is an excellent chelating agent and can be used as a reagent to test the acid resistance of building ceramic tiles. Citric acid-citrate buffer solution is used for flue gas desulfurization. Due to its low vapor pressure, non-toxicity, chemical stability, and high SO2 absorption rate, it is a highly valuable desulfurization absorbent.

Citric acid can be used as a formaldehyde-free dyeing and finishing agent to improve the wearing performance of fabrics or give them water-repellent and oil-repellent properties.

Citrate esters, approved by the US Food and Drug Administration, are used as non-toxic plasticizers for food packaging polyvinyl chloride and cellulose plastic films. Acetylated and butyrylated citrate esters can be used as foaming agents for methyl methacrylate polymers, stabilizers for acrylamide, initiators for polyamide adhesives, and plasticizers for polyvinyl chloride. Particularly, butyl citrate and acetylated tributyl citrate are globally recognized as non-toxic plasticizers. Besides being non-toxic, they have superior properties in terms of compatibility, resistance to extraction, and low volatility. For example, acetylated trihexyl citrate and butyrylated tributyl citrate can be used to produce components such as high-hygiene requirement blood transfusion tubes and catheters.

Killing bacteria and blood coagulation process
The combination of citric acid and 80℃ temperature has a good effect on killing bacterial spores and can effectively kill bacterial spores in the tubing of hemodialysis machines. In the formation of prothrombin activator and subsequent blood coagulation process, calcium ions must be involved. Citrate ions can form a stable and poorly dissociable soluble complex with calcium ions, thereby reducing the concentration of calcium ions in the blood and hindering blood coagulation.

Animal husbandry
Citric acid is formed in the tricarboxylic acid cycle in the body from acetyl-CoA and oxaloacetic acid and participates in the metabolism of sugar, fat, and protein. Natural citric acid exists in the fruits of plants (such as lemons, oranges, pineapples, etc.) and in the bones, muscles, and blood of animals. It can be artificially synthesized through the fermentation of sugar-containing substances such as sugar, molasses, starch, and grapes. Adding citric acid to compound feed can disinfect, prevent mold, and prevent infections such as Salmonella in animal feed. Feeding citric acid to animals can reduce the proliferation of pathogens and inhibit the production of toxic metabolites, thereby enhancing the stress resistance of animals [25].

(1) Increase feed intake and promote the digestion and absorption of nutrients
Adding citric acid to the daily diet of livestock can directly stimulate the taste cells in the mouth, increase saliva secretion, act as a flavoring agent, enhance animal appetite, and thereby increase feed intake. Adding citric acid to the diet can lower the pH of the feed. After animals consume it, the acidity in the stomach increases, inactive pepsinogen is converted into active pepsin, or it directly stimulates the secretion of digestive enzymes; In addition, when acidic chyme enters the small intestine, it stimulates the secretion of enterogastrone by the small intestine, which reflexively inhibits gastric motility and delays gastric emptying time, thereby increasing the time chyme spends in the intestine and promoting the digestion of nutrients [25].

(2) Promoting the health of intestinal flora
Organic acids can enter the cell walls of bacteria, causing pH gradient changes both inside and outside the bacteria, and inhibiting bacterial growth. Common pathogenic bacteria typically grow in a neutral to slightly alkaline pH range, such as Escherichia coli, which thrives at pH 6.0 to 8.0, and Streptococcus, which prefers pH 6.0 to 7.5. In contrast, beneficial bacteria like Lactobacillus thrive in acidic environments. Citric acid lowers the pH in the gastrointestinal tract, providing favorable growth conditions for Lactobacillus and other beneficial bacteria, thereby maintaining the normal balance of microbial flora in the digestive tracts of livestock and poultry [25].

(3) Enhancing the body's stress resistance and immune capacity
Immune active cells, namely T lymphocytes and B lymphocytes, play a role in immune surveillance for the body. Studies have shown that feeding citric acid to broiler chickens can increase the density of immune active cells, keeping the chickens in a better immune state, which can inhibit the reproduction of intestinal pathogenic bacteria and prevent the occurrence of infectious diseases [25].

(4) As a mold inhibitor and antioxidant
Citric acid is a natural preservative. By lowering the pH of feed, it inhibits the proliferation of harmful microorganisms and the production of toxins, thus having a significant anti-mold effect. As an enhancer for antioxidants, when citric acid is mixed with antioxidants, it can enhance the antioxidant effect, prevent or delay feed oxidation, improve the stability of compound feed, and extend its storage period.

Chemical production
Citric acid is a versatile precursor for many other organic compounds. Succinic acid can be obtained through the thermal isomerization of succinic anhydride, and the required succinic anhydride can be obtained by dry distillation of citric acid. Dehydrating citric acid with sulfuric acid can synthesize aconitic acid:

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