I. Food industry
Citric acid is the largest organic acid produced by biochemical methods in the world. Citric acid and salts are one of the pillar products of the fermentation industry and are mainly used in the food industry, such as sour agents, solubilizers, buffers, antioxidants, Deodorizing agents, flavor enhancers, gelling agents, toners, etc.
1), in terms of food additives, it is mainly used in carbonated drinks, fruit drinks, lactic acid drinks and other refreshing drinks and pickled products.
2) Adding citric acid to canned fruits can maintain or improve the flavor of the fruits, increase the acidity (lower pH value) of some fruits with low acidity when canned, weaken the heat resistance of microorganisms and inhibit their growth, and prevent acidity. Bacterial bloating and damage often occur with canned fruits.
3) Adding citric acid as a sour agent to candies can easily harmonize with the fruity flavor.
4) The use of citric acid in gel foods such as jams and jelly can effectively reduce the negative charge of pectin, thereby causing hydrogen bonding between pectin molecules and gelation.
5) When processing canned vegetables, some vegetables show an alkaline reaction. Using citric acid as a pH adjuster can not only play a seasoning role, but also maintain their quality.
6) Citric acid's chelating and pH-adjusting properties enable it to increase antioxidant properties, inhibit enzyme activity, and extend the shelf life of food in the processing of quick-frozen foods.
II. Metal Cleaning
Citric acid is an organic acid produced through microbial fermentation. It is widely used in detergent production. Its specificity and chelation effect 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 grains, which are safe food-grade microorganisms. The use of citric acid will not have any impact on the environment. It is relatively easy to degrade under the action of microorganisms and heat. Its own chelating ability is also relatively strong. Mainly in time, citrate has relatively strong chelation of manganese ions and iron ions. The ability and usage effect are also outstanding. Citric acid in detergents also has outstanding corrosion inhibition properties. Pickling is an important link in chemical cleaning. Compared with inorganic acids, citric acid is relatively weak in acidity, so it is harmful to the equipment. The corrosiveness produced is also relatively small, citric acid cleaning is relatively safe and reliable, the waste liquid is relatively easy to handle, and will not cause harm to the human body.
(1) Citric acid cleaning mechanism
Citric acid has little corrosion to metal 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 promotion effect of Fe3+ on corrosion.
Citric acid can dissolve iron oxide and copper oxide to form lemon iron and copper complexes. If ammoniated citric acid solution is used, it can form ferrous ammonia citrate and ferric citrate complexes with high solubility. The cleaning effect is Very good. Citric acid is mainly used to remove rust, so it is mainly used to clean newly built boilers. Citric acid is mixed with sulfamic acid, glycolic acid or formic acid and can be used to clean calcium, magnesium scale and rust in boilers. Citric acid and ethylene glycol can Aminetetraacetic acid (EDTA) is mixed and can be used to clean the superheater.
Citric acid and its derivatives have broad 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 water flow and pneumatics to produce water flow oscillation, which peels off the old scale in the water pipes, leaving the water pipes smooth and clean.
(3) Use compound surfactant to clean gas water heaters
Use chemical cleaning agents prepared from citric acid, AES and benzotriazole to clean gas water heaters that have been used for many years. Inject the cleaning agent into the inverted water heater. After soaking for 1 hour, pour out the cleaning solution, rinse it with clean water, and reuse the water heater. Under the same flow rate, the outlet water temperature increases by 5°C to 8°C.
(4) Clean the water dispenser
Dilute edible citric acid (powder) with water, pour it into the heated inner tank of the water dispenser, and soak for about 20 minutes. Finally, rinse the inner tank repeatedly with clean water until it is clean. It is non-toxic and effective.
III. Fine chemical industry
Citric acid is a type of fruit acid that can speed up cuticle renewal and is commonly used in lotions, creams, shampoos, whitening products, anti-aging products, acne products, etc. Citric acid can be used as experimental reagents, chromatographic analysis reagents and biochemical reagents 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 citrate as a builder can improve the performance of washing products, quickly precipitate metal ions, prevent pollutants from re-attaching to fabrics, and maintain the necessary alkalinity for washing; it can disperse and suspend dirt and ash; It is an excellent chelating agent that improves the performance of surfactants; it can be used as a reagent to test the acid resistance of building ceramic tiles. Citric acid-sodium citrate buffer 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 SO2 absorption rate.
Citric acid can be used as a formaldehyde-free dyeing and finishing agent to improve the wearing properties of fabrics or make fabrics water-repellent 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 butylated citrates can be used as foaming agents for methyl methacrylate polymers, stabilizers for acrylamide, initiators for polyamide adhesives, and plasticizers for polyvinyl chloride, etc. In particular, butyl citrate and acetylated tributyl citrate are world-recognized non-toxic plasticizers. In addition to being non-toxic, it has superior performance in terms of compatibility, extraction resistance, and low volatility. For example, acetylated trihexyl citrate and butyrylated tributyl citrate can be used to produce transfusion tubes and catheters with high hygiene requirements.
Sterilization and coagulation process
The combined effect of citric acid and 80°C temperature has a good effect on killing bacterial spores, and can effectively kill bacterial spores contaminated in the pipelines of hemodialysis machines. Calcium ions must participate in the formation of prothrombin activator and subsequent coagulation process. Citrate ions and calcium ions can form a soluble complex that is difficult to dissociate, thus reducing the concentration of calcium ions in the blood and hindering blood coagulation.
IV. Animal Breeding
Citric acid is carboxylated from acetyl-CoA and oxaloacetate in the tricarboxylic acid cycle of the body 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 citric acid is produced through the fermentation of 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, inhibit the production of toxic metabolites, and increase animal stress [25].
(1) Increase feed intake and promote digestion and absorption of nutrients
Adding citric acid to livestock diets can directly stimulate the taste bud cells in the mouth, increase saliva secretion, act as a flavoring agent, enhance the animal's appetite, and thereby increase the animal's feed intake. Adding citric acid to the diet can lower the pH of the feed. After the animal eats, the acidity in the stomach increases, and inactive pepsinogen is converted into active pepsin, or directly stimulates the secretion of digestive enzymes; in addition, acidic chyme After entering the small intestine, it stimulates the secretion of enterogastrin in the small intestine, causing it to reflexively inhibit gastric motility, delay gastric emptying, increase the time for chyme to pass through the intestine, and promote the digestion of nutrients.
(2) Promote the health of intestinal flora
Organic acids can enter the cell wall of bacteria, causing pH gradient changes inside and outside the bacteria, inhibiting bacterial growth. The suitable pH for the growth of several common pathogenic bacteria is neutral to alkaline. For example, the suitable pH for Escherichia coli is 6.0 to 8.0, Streptococcus is 6.0 to 7.5, and probiotics such as lactic acid bacteria are suitable for breeding in an acidic environment. Citric acid reduces the pH in the gastrointestinal tract and provides good growth conditions for probiotics such as lactic acid bacteria in the intestine, 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
Immune active cells, namely T lymphocytes and B lymphocytes, play an immune surveillance role in the body. Studies have shown that feeding citric acid to broiler chickens can increase the density of immune active cells, put the chickens in a better immune state, inhibit the reproduction of intestinal pathogenic bacteria and prevent the occurrence of infectious diseases .
(4) As an antifungal agent 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 obvious anti-fungal effects. As an antioxidant synergist, mixing citric acid with antioxidants can improve the antioxidant effect, prevent or delay feed oxidation, improve the stability of compound feeds and extend the storage period.
V. Chemical production
Citric acid is a versatile precursor to many other organic compounds. Citraconic acid can be produced by the thermal isomerization reaction of citraconic anhydride, and the required citraconic anhydride can be obtained by dry distillation of citric acid. Aconitic acid can be synthesized by dehydrating citric acid with sulfuric acid:
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I. Food industry
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