Citric acid is the largest acid among organic acids. Because of its physical, chemical and derivative properties, it is the most important organic acid, which is widely used in food, medicine, daily chemical and other industries.
1. Used in food industry; Because of its mild and refreshing sour taste, citric acid is widely used to make various drinks, soda, wine, candy, snacks, biscuits, canned fruit juice, dairy products and other foods. In all organic acid markets, the market share of citric acid is above 70%, and so far there is no sour agent that can replace citric acid. One molecule of crystal water citric acid is mainly used as an acidic flavoring agent for refreshing drinks, fruit juice, jam, fruit candy and canned food, and can also be used as an antioxidant for edible oil. At the same time, it can improve the sensory characteristics of food, enhance appetite and promote the digestion and absorption of calcium and phosphorus in the body. Anhydrous citric acid is widely used in solid drinks. Salts of citric acid, such as calcium citrate and iron citrate, are fortifiers that need to add calcium ions and iron ions to some foods. Esters of citric acid, such as triethyl citrate, can be used as nontoxic plasticizers to make plastic films for food packaging, and as acidulants and preservatives in beverage and food industries.
2. Used in chemical industry and textile industry: citric acid can be used as a reagent for chemical analysis in chemical technology, as an experimental reagent, a chromatographic analysis reagent and a biochemical reagent; Used as complexing agent and masking agent; Used to prepare buffer solution. Using citric acid or citrate as builder can improve the performance of washing products, quickly precipitate metal ions, prevent pollutants from reattaching to fabrics, and maintain the alkalinity necessary for washing; Disperse and suspend dust and ashes; It is an excellent chelating agent to improve the performance of surfactants; It can be used as a reagent to detect the acid resistance of building tiles.
Clothing formaldehyde pollution is a very sensitive issue. Citric acid and modified citric acid can be made into formaldehyde-free crease-resistant finishing agent, which can be used for crease-resistant finishing of cotton fabric. Not only the anti-wrinkle effect is good, but also the cost is low.
3. Used for environmental protection: citric acid-sodium citrate buffer is used for flue gas desulfurization. China is rich in coal resources, which is the main source of energy. However, there has been a lack of effective flue gas desulfurization technology, which leads to serious SO2 pollution in the atmosphere. At present, the annual emission of SO2 in China is nearly 40 million tons, so it is urgent to study effective desulfurization technology. Citric acid-sodium citrate buffer solution has low vapor pressure, non-toxicity, stable chemical properties and high SO2 absorption rate, so it is a desulfurization absorbent with great development value.
4. Used in livestock production: adding citric acid to piglet feed can wean early, improve feed utilization rate by 5% ~ 10%, and increase litter size of sows. Adding 1% ~ 2% citric acid to the diet of growing-finishing pigs can increase daily gain, reduce feed-meat ratio, increase protein digestibility, reduce back fat thickness and improve meat quality and carcass characteristics. Rare earth citrate is a new and efficient feed additive, which is suitable for pigs, chickens, fish, shrimp, cattle, sheep, rabbits, silkworms and other animals. It has the characteristics of promoting animal growth, improving product quality, improving disease resistance and survival rate, improving feed conversion rate and shortening feeding cycle.
5. Used in cosmetics: Citric acid is a kind of fruit acid, and its main function is to accelerate keratin renewal. It is often used in lotions, creams, shampoos, whitening products, anti-aging products and acne products. The renewal of keratin contributes to the shedding of melanin, the shrinking of pores and the dissolution of blackheads.
6. Used for sterilization: citric acid and the temperature of 80℃ have a good killing effect on bacterial spores, which can effectively kill contaminated bacterial spores in the pipeline of hemodialysis machine. Lemon, which enjoys the reputation of "king of western food", has a strong bactericidal effect and is very beneficial to food hygiene. In addition, people always like to make cold dishes with lemons, which are not only delicious and refreshing, but also stimulate appetite.
7. Used in medicine: In the formation of prothrombin activator and the subsequent coagulation process, calcium ions must participate. Citrate ion and calcium ion can form a soluble complex which is difficult to dissociate, thus reducing the concentration of calcium ion in blood and blocking blood coagulation. This product is used as an anticoagulant in vitro when blood transfusion or laboratory blood samples are anticoagulated.
8. Chemical processing or deep processing of citric acid: In addition to the above-mentioned uses of citric acid itself, another main use of citric acid is deep processing, which is a colorful industrial chain.