citric acid

Citric acid (carbon one), also known as Citric acid ，It is an important organic weak acid. It is a colorless crystal, odorless, easily soluble in water, and its solution is acidic. In biochemistry, it is an intermediate in the citric acid cycle (tricarboxylic acid cycle), which occurs in the metabolism of all aerobic organisms. Citric acid is widely used as an acidity regulator (national standard 2760-2014), flavoring agent and Chelating agents 。

Application areas:

Food Industry

Citric acid is the world's largest organic acid produced by biochemical methods. Citric acid and its salts are one of the mainstay products of the fermentation industry and are mainly used in the food industry as acidulants, solubilizers, buffers, antioxidants, deodorants, flavor enhancers, gelling agents, colorants, etc.

In terms of food additives, it is mainly used in carbonated beverages, fruit juice drinks, lactic acid drinks and other refreshing drinks and pickled products. Its demand varies with seasonal climate changes. Citric acid accounts for about 2% of the total consumption of acidulants./3。Adding citric acid to canned fruit can maintain or improve the flavor of the fruit and increase the acidity of some low-acid fruits during canning (reducingpHvalue), weakening the heat resistance of microorganisms and inhibiting their growth, preventing bacterial bulging and damage that often occurs in canned fruits with low acidity. Adding citric acid as an acidifier in candies can easily coordinate with the fruit flavor. Using citric acid in gel foods such as jams and jellies can effectively reduce the negative charge of pectin, thereby allowing hydrogen bonds between pectin molecules to gel. When processing canned vegetables, some vegetables have alkaline reactions, and using citric acid aspHAs a regulator, it not only plays a role in seasoning, but also maintains its quality.pHIts worthy properties enable it to increase the performance of antioxidants, inhibit enzyme activity and extend the shelf life of food during the processing of quick-frozen foods.

Metal Cleaning

Citric acid is an organic acid produced by microbial fermentation. It is widely used in detergent production. Its own specificity and chelation play a positive role. In the actual use process, citric acid has good performance, mainly in terms of safety. The raw materials for preparing citric acid are all derived from grain, which is a safe food-grade microorganism. The use of citric acid will not affect the environment. It is easy to degrade under the action of microorganisms and heat. Its own chelating ability is also relatively strong. The main time is that citrate has a strong chelating ability for manganese ions and iron ions, and the use effect is also outstanding. The corrosion inhibition of citric acid in detergents is also outstanding. Pickling is an important link in chemical cleaning. Compared with inorganic acids, the acidity of citric acid is relatively weak, so the corrosion to the equipment is also relatively small. The safety and reliability of citric acid cleaning are relatively strong, and the waste liquid is relatively easy to handle, which will not cause harm to the human body.

（1）Citric Acid Cleaning Mechanism

Citric acid has little corrosion to metals and is a safe cleaning agent. Since citric acid does not contain chloride ions, it will not cause stress corrosion of equipment. It can complex iron 3+，Weakened Iron 3+The promotion of corrosion.

Citric acid can dissolve iron oxide and copper oxide to form citric iron and copper complexes. If an ammoniated citric acid solution is used, it can generate highly soluble ferrous citrate and ferric citrate complexes, which have a very good cleaning effect. Citric acid is mainly used to remove rust, so it is mainly used to clean newly built boilers. Citric acid mixed with aminosulfonic acid, glycolic acid or formic acid can be used to clean calcium and magnesium scale and rust in boilers. Citric acid and ethylenediaminetetraacetic acid (EDTA）Mixed use, can be used to clean superheater.

Citric acid and its derivatives have a wide range of uses in many fields such as chemical cleaning due to their special physical and chemical properties.

（2）Citric Acid Pipe Cleaning

This is the latest cleaning technology for hard water with high impurities. It uses food-grade citric acid to soften stubborn scale, and then uses a microcomputer to control the water flow and pneumatics to generate water flow oscillations, which peels off the old scale in the water pipes and keeps the water pipes unobstructed and clean.

（3）Cleaning gas water heaters with compound surfactants Citric acid,AESThe chemical cleaning agent prepared with benzotriazole and benzotriazole was used to clean the gas water heater that had been used for many years. The cleaning agent was injected into the inverted water heater, soaked for 1 hour, poured out the cleaning liquid, rinsed with clean water, and reused the water heater. At the same flow rate, the water outlet temperature increased by 5℃～8℃ 。

（4）Cleaning the water dispenser

Dilute edible citric acid (powdered) with water, inject it into the heating tank of the water dispenser, and soak it for about 20 minutes. Finally, rinse the tank repeatedly with clean water until it is clean. It is non-toxic and has good effects.[5]。

Fine Chemicals

Citric acid is a kind of fruit acid, which can accelerate the renewal of cuticle and is often used in lotions, creams, shampoos, whitening products, anti-aging products, acne products, etc. In chemical technology, citric acid can be used as experimental reagents, chromatographic analysis reagents and biochemical reagents; used as chelating agents, masking agents; and used to prepare buffer solutions. Using citric acid or citrates as detergents can improve the performance of washing products, quickly precipitate metal ions, prevent pollutants from reattaching to fabrics, maintain the alkalinity necessary for washing, disperse and suspend dirt and ash, improve the performance of surfactants, and is an excellent chelating agent; It can be used as a reagent to test the acid resistance of architectural ceramic tiles. Citric acid-sodium citrate buffer solution is used for flue gas desulfurization. Citric acid-sodium citrate buffer solution is a desulfurization absorbent with great development value due to its low vapor pressure, non-toxicity, stable chemical properties, and high absorption rate of sulfur dioxide.

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

Citrate esters have been approved by the U.S. 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, plasticizers for polyvinyl chloride, etc. In particular, butyl citrate and acetylated tributyl citrate are universally recognized non-toxic plasticizers. In addition to being non-toxic, they are also superior in terms of compatibility, extraction resistance, and low volatility. For example, acetylated trihexyl citrate and butyrylated tributyl citrate can be used to produce component blood transfusion tubes and catheters with high hygiene requirements.

Sterilization and coagulation process

Citric acid and 80 ℃The combined effect of temperature has a good effect of killing bacterial spores, and can effectively kill bacterial spores contaminated in the hemodialysis machine pipeline. Calcium ions must participate in the formation of prothrombin activators and the subsequent coagulation process. Citrate ions and calcium ions can form a soluble complex that is difficult to dissociate, thereby reducing the calcium ion concentration in the blood and hindering blood coagulation.

Animal farming

Citric acid is formed by the carboxylation of acetyl coenzyme A and oxaloacetate in the body's tricarboxylic acid cycle and participates in the metabolism of sugar, fat and protein in the body. Natural citric acid exists in the fruits of plants (such as lemons, citrus, pineapples, etc.) and the bones, muscles and blood of animals. Artificial synthesis is produced by fermenting sugar, molasses, starch, grapes and other sugar-containing substances. Adding citric acid to compound feed can disinfect, prevent mildew, and prevent salmonella and other infections in animal feed. Animals eating citric acid can reduce the proliferation of pathogens and inhibit the production of toxic metabolites, thereby improving animal stress resistance.[25]。

（1）Increase feed intake and promote nutrient digestion and absorption

Adding citric acid to livestock diets can directly stimulate the taste buds in the mouth, increase saliva secretion, act as a flavoring agent, enhance animal appetite, and thus increase animal feed intake.pHAfter the animal eats, the acidity in the stomach increases, and the inactive pepsinogen is converted into active pepsin, or the secretion of digestive enzymes is directly stimulated; in addition, after the acidic chyme enters the small intestine, it stimulates the small intestine to secrete enterogastrone, which reflexively inhibits gastric peristalsis, delays the time of gastric emptying, prolongs the time for chyme to pass through the intestine, and promotes the digestion of nutrients.[25]。

（2）Promotes healthy intestinal flora

Organic acids can enter the bacterial cell wall, causing the inside and outside of the bacteria to appearpHGradient changes inhibit bacterial growth. Suitable growth conditions for several common pathogenspHAll are neutral and alkaline, such as Escherichia colipH6.0～8.0，Streptococcus is 6.0～7.5，Probiotics such as lactic acid bacteria thrive in an acidic environment.pHDecreased, probiotics such as lactic acid bacteria in the intestines get good growth conditions, thus maintaining the normal balance of microbial flora in the digestive tract of livestock and poultry.

（3）Enhance the body's anti-stress and immune capabilities

Immunocompetent cells, namely TV lymphocytes and B lymphocytes, play an immune surveillance role in the body. Studies have shown that feeding citric acid to broilers can increase the density of immunocompetent cells, keep the chickens in a better immune state, inhibit the reproduction of intestinal pathogens and prevent the occurrence of infectious diseases.

（4）As mildew inhibitor and antioxidant

Citric acid is a natural preservative. Since citric acid can reduce the pH value of feed, the proliferation of harmful microorganisms and the production of toxins are inhibited, and it has a significant anti-mold effect. As a synergist of antioxidants, mixing citric acid with antioxidants can improve the antioxidant effect, prevent or delay feed oxidation, improve the stability of compound feed and extend the storage period.