What is the main use of citric acid

Citric acid is the largest organic acid, soluble in water, and is a natural preservative and food additive. According to its water content, it can be divided into citric acid monohydrate and anhydrous citric acid. Because of its physical properties, chemical properties and derivative properties, it is the most important organic acid widely used in food, medicine, daily chemical and other industries. So, what are the specific functions and uses of citric acid?

1. Effect of citric acid

Citric acid is mainly used as an acidifying agent, a solvent, a buffer, an antioxidant, a deodorant, a flavor enhancer, a gelling agent, a toner, etc. In addition, citric acid can also inhibit bacteria, protect color, improve flavor and promote sucrose conversion. Citric acid also has chelating effect and can remove some harmful metals. Citric acid can prevent oxidation caused by enzyme catalysis and metal catalysis, thus preventing discoloration and flavor change of quick-frozen fruit.

2.Use of citric acid

A. For food industry

Because citric acid has a mild and refreshing sour taste, in terms of food additives, it is mainly used in carbonated drinks, fruit juice drinks, lactic acid drinks and other cool drinks and pickled products, and its demand varies with seasonal climate changes. Citric acid accounts for about 2/3 of the total consumption of acid flavor agent. Adding citric acid to canned fruit can maintain or improve the flavor of fruits in the museum, increase the acidity of some fruits with low acidity (lower pH value), weaken the heat resistance of microorganisms and inhibit their growth, and prevent the bacterial expansion and destruction of canned fruits with low acidity. Adding citric acid into candy as an acid is easy to coordinate with fruit taste. The use of citric acid in gel food, jam and jelly can effectively reduce the negative charge of pectin, so that the hydrogen bond between pectin molecules can bind to gel. When processing canned vegetables, some vegetables show alkaline reaction. Using citric acid as pH regulator can not only play a role in seasoning, but also maintain its quality. Citric acid has the characteristics of chelation and pH regulation, which can increase the performance of antioxidants, inhibit enzyme activity, and extend the shelf life of foods in the processing of quick-frozen foods.

Citric acid monohydrate is mainly used as an acidic flavoring agent for cool drinks, fruit juice, jam, fruit sugar and canned food, and also as an antioxidant for edible oil. At the same time, it can improve the sensory properties 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. Citric acid salts, such as calcium citrate and iron citrate, are fortifiers that need to be added with calcium and iron ions in some foods. Esters of citric acid, such as triethyl citrate, can be used as non-toxic plasticizers, making plastic films for food packaging, and as acid and preservative in the beverage and food industry.

B. For water treatment industry

Citric acid can sterilize and regulate the pH value of water in water treatment. The acidity of citric acid can change the pH value of cells and affect the normal metabolism of bacteria. High concentration of acidic hydrogen ions can also change the biological activity of bacteria and directly damage cells.

C.For chemical reagent and washing

Citric acid can be used as chemical analysis reagent in chemical technology, as experimental reagent, chromatographic analysis reagent and biochemical reagent; It is used as complexing agent and masking agent to prepare buffer solution.

Using citric acid or citrate as a detergent aid can improve the performance of washing products, rapidly precipitate metal ions, prevent pollutants from re-attaching to the fabric, maintain the necessary alkalinity for washing, disperse and suspend dirt and ash, and improve the performance of surfactants.

Citric acid can also be made into formaldehyde-free anti-crease finishing agent for anti-crease finishing of pure cotton fabrics.

D.For cosmetics

Citric acid can prevent and eliminate skin pigmentation. Citric acid is a kind of fruit acid, which is mainly used to accelerate the renewal of cutin, and is commonly used in lotion, cream, shampoos, whitening products, anti-aging products, acne products, etc. The renewal of cutin is helpful for skin melanin peeling, pore thinning, blackhead dissolution, etc.

E.For environmental protection

China is rich in coal resources, which constitute the main part of energy. However, there has been a lack of effective flue gas desulfurization technology, resulting in serious atmospheric SO2 pollution. At present, the annual emission of SO2 in China has reached nearly 40 million tons. It is urgent to study effective desulfurization technology. Because of its low vapor pressure, non-toxic, stable chemical properties and high SO2 absorption rate, citric acid-sodium citrate buffer solution is a desulfurization absorbent with great development value.

F. For livestock additives

Adding citric acid to piglet feed can wean early, improve feed utilization rate by 5%~10%, and increase sow litter size. Adding 1%~2% citric acid to the diet of growing-finishing pigs can increase daily gain, reduce the ratio of feed to meat, improve protein digestibility, reduce the thickness of back fat, and improve meat quality and carcass characteristics.

G. For sterilization

The combined action of citric acid and 80 ℃ has a good effect on killing bacterial spores, and can effectively kill bacterial spores contaminated in the pipeline of hemodialysis machine. Lemon, which enjoys the reputation of "king of western food", has a strong bactericidal effect and is good for food hygiene. In addition to the fragrance of lemon, people have always liked to use it to make cold dishes. It is not only delicious and refreshing, but also can improve appetite, such as the very popular "lemon chicken feet" recently.

H. For medicine

Citric acid, also known as citric acid, must have calcium ions in the formation of prothrombin activator and subsequent coagulation process. Citrate ion and calcium ion can form a soluble complex that is difficult to dissociate, thus reducing the concentration of calcium ion in blood and preventing blood coagulation. It is used as anticoagulant in vitro during blood transfusion or anticoagulation of laboratory blood samples.

3. Precautions

A. Industrial hazards

Health hazard: concentrated citric acid solution has irritation on mucous membrane. In industrial use, the contact may cause eczema;

Explosion hazard: citric acid is flammable. The powder and air can form explosive mixture, which may cause combustion and explosion in case of open fire, high heat or contact with oxidant.

B. Storage conditions

Citric acid monohydrate loses crystal water in dry air or when heated to about 40 ℃, and deliquests slightly in wet air. The dilute citric acid aqueous solution can ferment when standing still. Therefore, solid monohydrate or anhydrous substances should be stored in airtight containers in a cool and dry place.