Citric Acid Anhydrous Food Grade

Product Name: Citric acid anhydrous

CAS Number: 77-92-9
EINECS Number: 201-069-1
Chemical Formula: C6H8O7
Melting Point: 153 - 159 °C
Boiling Point: 309.6 ± 42.0 °C (760 mmHg)
Vapor Density: 7.26 (compared to air)
Vapor Pressure: < 0.1 hPa (at 20 °C)
Refractive Index: 1.493 - 1.509
Flash Point: 155.2 ± 24.4 °C
Solubility: Soluble in water, ethanol, 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)

Citric acid can exist in either anhydrous or monohydrate form. The crystalline form of citric acid varies depending on the crystallization conditions. It is slightly hygroscopic in dry air and has hygroscopicity in humid air. Heating can decompose it into various products and it can react with acids, bases, glycerol, etc. Anhydrous citric acid is crystallized from hot water, while monohydrate citric acid is crystallized from cold water. Monohydrate citric acid can lose its bound water at around 78 °C to convert into anhydrous citric acid. Citric acid can also dissolve in anhydrous ethanol at 15 °C (76 parts of citric acid per 100 parts of ethanol) and can react with ethanol to form citric acid ethyl ester. When the temperature exceeds approximately 175 °C, citric acid will decompose and release carbon dioxide.

Food Industry
Citric acid is the most produced organic acid through 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, such as ascorbic acid, emulsifier, buffer, antioxidant, deodorizer, flavor enhancer, gelling agent, colorant, etc. [22].
In terms of food additives, it is mainly used in refreshing beverages like carbonated drinks, fruit juices, and lactic acid beverages, as well as pickled products. The demand for citric acid varies with seasonal and climatic changes. Citric acid accounts for approximately two-thirds of the total consumption of ascorbic acid. In canned fruits, adding citric acid can maintain or improve the flavor of fruits and increase the acidity of fruits with lower acidity during canning (lowering the pH value), weakening the heat resistance of microorganisms and inhibiting their growth, preventing bacterial spoilage and damage in canned fruits with low acidity. In candies, adding citric acid as an ascorbic acid agent is easy to coordinate with the fruit flavor. In gel foods such as sauces and jellies, using citric acid can effectively reduce the negative charge of pectin, allowing hydrogen bonds between pectin molecules to form a gel. In processing vegetable canned foods, some vegetables have a basic reaction, using citric acid as a pH adjuster not only has a flavoring effect but also can maintain their quality. The chelating and pH-regulating properties of citric acid make it possible to increase the antioxidant performance in frozen food processing, inhibit enzyme activity, and extend food preservation period [23].
Metal Cleaning
Citric acid is an organic acid produced through microbial fermentation and is widely used in detergent production. Its own specificity and chelating effect play a positive role. In actual use, citric acid has good performance, mainly in terms of safety, as the raw materials for preparing citric acid are all derived from grains, which are safe food-grade microorganisms. The use of citric acid does not cause any impact on the environment. It is relatively easy to degrade under the action of microorganisms and heat, and its own chelating ability is also strong. Mainly because citrate has strong chelating ability for manganese ions and iron ions, and the use effect is also prominent. The corrosion inhibition performance of citric acid in detergent use is also prominent. Acid washing, as an important part of chemical cleaning, is relatively important compared to inorganic acids. Citric acid has a relatively weak acidity and thus causes less corrosion to equipment compared to inorganic acids. The safety and reliability of citric acid cleaning are strong, and the waste liquid is relatively easy to handle, without causing harm to the human body [24].
(1) Mechanism of Citric Acid Cleaning
Citric acid has low 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 complex Fe3+ and weaken the promoting effect of Fe3+ on corrosion.
Citric acid can dissolve iron oxide and copper oxide, generating citric iron and copper complexes. If using ammonia-treated citric acid solution, it can generate very soluble citric iron-ammonium and citric ferric complexes, with excellent cleaning effect. Citric acid mainly removes rust, so it is mainly used for cleaning newly built boilers. Citric acid can be mixed with aminosulfonic acid, hydroxyacetic acid or formic acid to clean calcium and magnesium scale and rust in boilers. Citric acid can be mixed with ethylenediaminetetraacetic acid (EDTA) to clean superheaters [5].
Citric acid and its derivatives have very broad applications in many fields such as chemical cleaning.
(2) Cleaning Pipes with Citric Acid
This is the latest cleaning technology for high-impurity hard water. It uses food-grade citric acid to soften stubborn scale, and then uses a microcomputer to control water flow and air pressure to generate water flow oscillation, causing the accumulated scale in the pipes to peel off and become clean and unobstructed [3].
(3) Re-combining Surfactants for Cleaning Gas Water Heaters The chemical cleaning agent prepared with citric acid, AES and benzothiazole was used to clean the gas water heater that had been in use for many years. The cleaning agent was injected into the inverted water heater and left to soak for 1 hour. Then the cleaning liquid was drained and the water heater was rinsed with clean water. The water heater was reused. Under the same flow rate, the water temperature increased by 5℃ to 8℃ [5].
(4) Cleaning the water dispenser
Use edible citric acid (powder form) diluted with water and inject it into the heating inner tank of the water dispenser. Let it soak for about 20 minutes. Finally, rinse the inner tank with clean water repeatedly until it is clean. It is non-toxic and has a good effect [5].
Fine chemical field
Citric acid belongs to a type of fruit acid and can accelerate the renewal of keratin. It is often used in emulsions, creams, shampoos, whitening products, anti-aging products, acne products, etc. Citric acid can be used as an experimental reagent, chromatographic analysis reagent and biochemical reagent in chemical technology; it can be used as a complexing agent and masking agent; it can be used to prepare buffer solutions. Using citric acid or its salts as a detergent can improve the performance of cleaning products, quickly precipitate metal ions, prevent contaminants from re-attaching to the fabric, and maintain the necessary alkalinity for cleaning; it disperses and suspends dirt and dust; enhances the performance of surfactants, is an excellent chelating agent; can be used as a test reagent for the acid resistance of building ceramic tiles. Citric acid-citric acid sodium buffer solution is used for sulfur dioxide removal in flue gas. The citric acid-citric acid sodium buffer solution is due to its low vapor pressure, non-toxicity, stable chemical properties, and high absorption rate of SO2, etc., has great development value as a desulfurization absorption agent.
Citric acid can be used as a formaldehyde-free dyeing and finishing agent, improving the wearing performance of the fabric or giving the fabric water-repellent and oil-repellent properties.
Citrate esters, which have been approved by the US Food and Drug Administration as non-toxic plasticizers for polyvinyl chloride and cellulose plastic films used in food packaging. 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. Especially citrate butyrate and acetylated citrate tributyrate are recognized as non-toxic plasticizers. In addition to being non-toxic, they have superior performance in compatibility, extractability resistance, and low volatility. For example, acetylated citrate trihexylate and butyrylated citrate tributyrate can be used to produce components such as blood vessels and catheters with high hygiene requirements.
Bactericidal and coagulation process
The combination of citric acid and 80 ℃ temperature has a good bactericidal effect on spores and can effectively kill the spores of bacteria in the blood dialysis machine pipeline. In the formation of prothrombin activator and the subsequent coagulation process, calcium ions must participate. Citrate ions can form a soluble complex that is difficult to dissociate with calcium ions, thereby reducing the concentration of calcium ions in the blood and blocking blood coagulation.
Animal breeding
Citric acid is formed in the tricarboxylic acid cycle of the body from acetyl coenzyme A and oxaloacetic acid through condensation. It participates in the metabolism of sugar, fat and protein in the body. Natural citric acid is found in the fruits of plants (such as lemon, orange, pineapple, etc.) and in the bones, muscles and blood of animals. Artificial synthesis is obtained through fermentation of sugar substances such as sugar cane, molasses, starch, grapes, etc. Adding citric acid to the compound feed can disinfect, prevent mold, and prevent Salmonella and other infections of animal feed. Animals consuming citric acid can reduce the proliferation of pathogens and inhibit the production of toxic metabolites, improving the animal's stress resistance [25].
(1) Increase feed intake and promote nutrient digestion and absorption
Adding citric acid to the livestock diet can directly stimulate the taste buds cells in the mouth, increase saliva secretion, play a role as a flavoring agent, enhance animal appetite, and thereby increase the animal's feed intake. Adding citric acid to the diet can lower the pH of the feed, and after the animals consume it, the acidity in the stomach increases, inactive pepsinogen is converted into active pepsin, or directly stimulates the secretion of digestive enzymes; Additionally, when acidic chyme enters the small intestine, it stimulates the secretion of intestinal inhibitory gastrin, which reflexively inhibits gastric peristalsis, delays the gastric emptying time, and prolongs the time for chyme to pass through the intestinal tract, thereby promoting the digestion of nutrients [25].
(2) Promote intestinal flora health
Organic acids can enter the cell walls of bacteria, causing pH gradient changes inside and outside the bacteria, and inhibiting bacterial growth. The pH suitable for the growth of several common pathogenic bacteria is neutral to slightly alkaline, such as Escherichia coli with an optimal pH of 6.0-8.0, Streptococcus with 6.0-7.5, while lactic acid bacteria and other probiotics are suitable for acidic environments for reproduction. Citric acid lowers the pH in the gastrointestinal tract, providing favorable growth conditions for probiotics such as lactobacilli in the intestinal tract, thereby maintaining the normal balance of microflora in the digestive tract of livestock and poultry [25].
(3) Enhance the body's stress resistance and immune capacity
Immune-active cells, namely T lymphocytes and B lymphocytes, play an immune surveillance role in the body. Studies have shown that feeding meat chickens with citric acid can increase the density of immune-active cells, place the chickens in a better immune state, and inhibit the reproduction of intestinal pathogenic bacteria and prevent the occurrence of infectious diseases [25].
(4) Use as a mold inhibitor and antioxidant
Citric acid is a natural preservative. Because citric acid can lower the pH of the feed, the proliferation of harmful microorganisms and the production of toxins are inhibited, and it has a significant anti-mold effect. As an enhancer of antioxidant synergists, mixing citric acid with antioxidant agents can improve the antioxidant effect, prevent or delay feed oxidation, improve the stability of formulated feed and extend the storage period.
Chemical production
Citric acid is a multifunctional precursor for many other organic compounds. Citric acid can be obtained through the thermal isomerization reaction of citric acid anhydride, and the required citric acid anhydride can be obtained from the dry distillation of citric acid. Dehydration with sulfuric acid can synthesize aconitic acid:
The dehydrocoupling reaction of citric acid in fuming sulfuric acid can also be used to prepare acetaldicarboxylic acid. 

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